Motor drive device having failure detection function

Abstract

This motor drive device comprises: an inverter that is a three-phase bridge circuit in which each of the upper arm on the high potential side and lower arm on the low potential side of each of three phases is provided with a switching element; a power line that supplies the AC voltage output from an inverter to a motor; a current detection unit that detects the value of current output from the inverter; an overcurrent detection unit that detects the presence or absence of an overcurrent flowing through the upper arm or the lower arm; a voltage detection unit that detects the value of the DC voltage; a dynamic brake circuit that is connected between the current detection unit in the power line and the motor and is capable of short-circuiting between phases of the windings of the motor via a resistor by closing switches; a switching command unit that commands a switching operation of each switching element; a dynamic brake command unit that commands an opening / closing operation of each switch; and a failure detection unit that detects a failure in the motor drive device on the basis of respective detection results by the current detection unit, the overcurrent detection unit, and the voltage detection unit when the switching operation of each switching element is commanded by the switching command unit and the opening / closing operation of each switch is commanded by the dynamic brake command unit.

Description

Motor drive device with fault detection function

[0001] The present disclosure relates to a motor drive device having a fault detection function.

[0002] In a motor drive device, AC power output from an inverter is supplied to the motor via a power line. A dynamic braking circuit is widely used to brake the motor. The dynamic braking circuit consists of a dynamic braking circuit switch (hereinafter simply referred to as the "switch") provided between the input terminals of the motor and a dynamic braking resistor (DB resistor) connected in series with the dynamic braking circuit switch. When dynamic braking is applied, the supply of AC power to the motor from the inverter is interrupted, and the dynamic braking circuit switch is closed to short-circuit the motor input terminals (between the phases of the motor windings).

[0003] JP 2019-152456 A JP 2009-50059 A JP 2021-35150 A

[0004] There is a demand for a technology in a motor drive device that can detect, through a series of processes, any of open circuit faults and short circuit of switching elements in an inverter, open circuit faults and short circuit of switches in a dynamic braking circuit, breaks and ground faults in power lines connecting the inverter and motor, and short circuits between power lines.

[0005] According to one aspect of the present disclosure, a motor drive device includes an inverter including a three-phase bridge circuit in which switching elements are provided in each of an upper arm on the high potential side and a lower arm on the low potential side of each of three phases, the inverter converting a DC voltage of a DC link into an AC voltage by switching operations of the switching elements and outputting the AC voltage; a power line provided between the inverter and the motor and supplying the AC voltage output from the inverter to the motor; a current detection unit provided in the power line and detecting a value of a current output from the inverter; an overcurrent detection unit detecting presence or absence of an overcurrent flowing in the upper arm or the lower arm; a voltage detection unit detecting a value of the DC voltage; a dynamic braking circuit connected in the power line between the current detection unit and the motor, and capable of short-circuiting phases of motor windings via a resistor by closing a switch; a switching command unit that commands switching operations of each switching element; a dynamic braking command unit that commands opening and closing operations of each switch; and a fault detection unit that detects a fault in the motor drive device based on detection results by the current detection unit, the overcurrent detection unit, and the voltage detection unit when the switching command unit commands switching operations of each switching element and the dynamic braking command unit commands opening and closing operations of each switch.

[0006] FIG. 1 is a circuit diagram illustrating a motor drive device according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of a command pattern according to an embodiment of the present disclosure. FIG. 3 is a circuit diagram illustrating an example of a current path in a state in which a switching element of one phase of the upper arm and switching elements of two phases of the lower arm are in an ON state and three switches in the dynamic braking circuit are closed. FIG. 4 is a circuit diagram illustrating an equivalent circuit of the current path shown in FIG. 3. FIG. 4A is a circuit diagram illustrating a result of combining the impedances of the equivalent circuit shown in FIG. 4B. FIG. 6A is a circuit diagram illustrating a result of combining the impedances of the equivalent circuit shown in FIG. 6A. FIG. 7 is a diagram illustrating a determination criterion table showing the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q1 used in the state determination process by the determination unit. FIG. 8 is a diagram illustrating the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q2 used in the state determination process by the determination unit. FIG. 10 is a diagram showing a determination criterion table illustrating the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q3 used in the state determination process by the determination unit. FIG. 10 is a diagram showing a determination criterion table illustrating the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q4 used in the state determination process by the determination unit. FIG. 10 is a diagram showing a determination criterion table illustrating the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q5 used in the state determination process by the determination unit. FIG. 10 is a diagram showing a determination criterion table illustrating the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q6 used in the state determination process by the determination unit. FIG. 10 is a diagram showing a determination criterion table illustrating the relationship between the state of the motor drive device and combinations of current reference values ​​and the presence or absence of overcurrent in command pattern Q7 used in the state determination process by the determination unit. FIG. 10 is a diagram showing fault determination conditions used in the fault detection process by the determination unit. FIG. 10 is a flowchart showing the operation flow of fault determination process in the motor drive device according to an embodiment of the present disclosure.This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the U-phase upper arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the U-phase upper arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the U-phase upper arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the V-phase upper arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the V-phase upper arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the V-phase upper arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the W-phase upper arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the W-phase upper arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the W-phase upper arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the U-phase lower arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the U-phase lower arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when an open-circuit failure occurs in a switching element of the U-phase lower arm, showing the state of the motor drive device operating under command pattern Q3.This is a circuit diagram showing the state of a motor drive device when an open circuit failure occurs in a switching element of a V-phase lower arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when an open circuit failure occurs in a switching element of a V-phase lower arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when an open circuit failure occurs in a switching element of a W-phase lower arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when an open circuit failure occurs in a switching element of a W-phase lower arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when an open circuit failure occurs in a switching element of a W-phase lower arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a U-phase upper arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the switching element of the U-phase upper arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the switching element of the U-phase upper arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the switching element of the V-phase upper arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the switching element of the V-phase upper arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the switching element of the V-phase upper arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the switching element of the W-phase upper arm, showing the state of the motor drive device operating under command pattern Q1.This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a W-phase upper arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a W-phase upper arm, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a U-phase lower arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a U-phase lower arm, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a V-phase lower arm, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a V-phase lower arm, showing the state of the motor drive device operating under command pattern Q2.

[0023] Figure 1 is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a V-phase lower arm, the state showing the state of the motor drive device operating under command pattern Q3.

[0024] Figure 2 is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a W-phase lower arm, the state showing the state of the motor drive device operating under command pattern Q1.

[0025] Figure 3 is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a W-phase lower arm, the state showing the state of the motor drive device operating under command pattern Q2.

[0026] Figure 4 is a circuit diagram showing the state of a motor drive device when a short circuit occurs in a switching element of a W-phase lower arm, the state showing the state of the motor drive device operating under command pattern Q3.

[0027] Figure 5 is a circuit diagram showing the state of a motor drive device when an open fault occurs in a switch of two or more phases of a dynamic braking circuit, the state showing the state of the motor drive device operating under command pattern Q1.

[0023] Figure 1 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in a switch of two or more phases of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q2.

[0024] Figure 2 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in a switch of the U-phase of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q1.

[0025] Figure 3 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in a switch of the U-phase of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q2.

[0026] Figure 4 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in a switch of the V-phase of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q1.

[0027] Figure 5 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in a switch of the V-phase of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q2.

[0028] Figure 6 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in a switch of the W-phase of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q1.

[0023] Figure 1 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in the W-phase switch of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q2.

[0024] Figure 2 is a circuit diagram showing the state of the motor drive device when an open-circuit fault occurs in the W-phase switch of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q3.

[0025] Figure 3 is a circuit diagram showing the state of the motor drive device when a short-circuit occurs in the U-phase and V-phase switches of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q4.

[0026] Figure 4 is a circuit diagram showing the state of the motor drive device when a short-circuit occurs in the U-phase and V-phase switches of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q5.

[0027] Figure 5 is a circuit diagram showing the state of the motor drive device when a short-circuit occurs in the V-phase and W-phase switches of the dynamic braking circuit, the state of the motor drive device operating under command pattern Q4.

[0023] Figure 1 is a circuit diagram showing the state of the motor drive device when short-circuiting occurs in the W-phase and U-phase switches of the dynamic braking circuit, showing the state of the motor drive device operating under command pattern Q4.

[0024] Figure 2 is a circuit diagram showing the state of the motor drive device when short-circuiting occurs in all three-phase switches of the dynamic braking circuit, showing the state of the motor drive device operating under command pattern Q4.

[0025] Figure 3 is a circuit diagram showing the state of the motor drive device when a break occurs in the U-phase power line, showing the state of the motor drive device operating under command pattern Q6.

[0026] Figure 4 is a circuit diagram showing the state of the motor drive device when a break occurs in the V-phase power line, showing the state of the motor drive device operating under command pattern Q6.

[0027] Figure 5 is a circuit diagram showing the state of the motor drive device when a break occurs in the W-phase power line, showing the state of the motor drive device operating under command pattern Q6.

[0028] Figure 6 is a circuit diagram showing the state of the motor drive device when a break occurs in the W-phase power line, showing the state of the motor drive device operating under command pattern Q7.

[0029] Figure 7 is a circuit diagram showing the state of the motor drive device when a break occurs in two or more phase power lines, showing the state of the motor drive device operating under command pattern Q6. This is a circuit diagram showing the state of a motor drive device when a break occurs in two or more phase power lines, showing the state of the motor drive device operating under command pattern Q7. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between a U-phase power line and a V-phase power line, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between a U-phase power line and a V-phase power line, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between a U-phase power line and a V-phase power line, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between a V-phase power line and a W-phase power line, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between a V-phase power line and a W-phase power line, showing the state of the motor drive device operating under command pattern Q2.This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between the W-phase power line and the U-phase power line, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between the W-phase power line and the U-phase power line, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between the W-phase power line and the U-phase power line, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between all three-phase power lines, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between all three-phase power lines, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a motor drive device when a short circuit occurs between all three-phase power lines, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of a motor drive device when a ground fault occurs in the U-phase power line, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the U-phase power line, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the U-phase power line, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the U-phase power line, showing the state of the motor drive device operating under command pattern Q4. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the V-phase power line, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the V-phase power line, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the V-phase power line, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the V-phase power line, showing the state of the motor drive device operating under command pattern Q4.This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the W-phase power line, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the W-phase power line, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the W-phase power line, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of the motor drive device when a ground fault occurs in the W-phase power line, showing the state of the motor drive device operating under command pattern Q4. This is a circuit diagram showing the state of a normal motor drive device, showing the state of the motor drive device operating under command pattern Q1. This is a circuit diagram showing the state of a normal motor drive device, showing the state of the motor drive device operating under command pattern Q2. This is a circuit diagram showing the state of a normal motor drive device, showing the state of the motor drive device operating under command pattern Q3. This is a circuit diagram showing the state of a normal motor drive device, showing the state of the motor drive device operating under command pattern Q4. This is a circuit diagram showing the normal state of the motor drive device, showing the state of the motor drive device operating under command pattern Q5, this is a circuit diagram showing the normal state of the motor drive device, showing the state of the motor drive device operating under command pattern Q6, and this is a circuit diagram showing the normal state of the motor drive device, showing the state of the motor drive device operating under command pattern Q7.

[0007] Hereinafter, an embodiment of a motor drive device having a fault detection function will be described with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of those components may be omitted. The scale of the drawings has been appropriately changed to facilitate understanding.

[0008] In the following description, "electrically connected" may be simply referred to as "connected." A converter that converts AC voltage supplied from a three-phase AC power source into DC voltage and outputs it is also called a "rectifier," "rectifier device," "rectifier circuit," or "forward converter." An inverter that converts DC voltage into AC voltage and outputs it is also called an "inverter." A "DC link" refers to a circuit portion that electrically connects the DC output side of a converter and the DC input side of an inverter. A "DC link" is also called a "DC link section," "DC link," "DC link section," "DC bus," or "DC intermediate circuit." A "DC link voltage" refers to the potential difference between the positive potential of the positive power line of the DC link and the negative potential of the negative power line. The "on" operation of a switching element means that the switching element is closed, thereby forming an electric path through the switching element. The "off" operation of a switching element means that the switching element is opened, thereby interrupting the electric path through the switching element. An "on command" refers to a command to turn on a switching element. An "off command" refers to a command to turn off a switching element. "Closing" a switch in a dynamic braking circuit refers to the switch being closed, thereby establishing an electrical path through that switch. "Opening" a switch in a dynamic braking circuit refers to the switch being opened, thereby interrupting an electrical path through that switch. "Close command" refers to a command to close a switch. "Open command" refers to a command to open a switch. "Open-circuit fault of a switching element" refers to a failure in which a switching element does not turn on despite being commanded to turn on. "Open-circuit fault of a switch in a dynamic braking circuit" refers to a failure in which a switching element does not close despite being commanded to close. "Short-circuit fault of a switching element" refers to a failure in which a switching element does not turn off despite being commanded to turn off. "Short-circuit fault of a switch in a dynamic braking circuit" includes both a failure of the switch itself, in which the switch does not open despite being commanded to open, and a short-circuit fault caused by foreign matter adhering to the switch contacts.Furthermore, in the following description, when a phrase "a switching command is sent to the control terminal (gate terminal or base terminal) of a switching element" is used, the phrase "to the control terminal" may be omitted and simply expressed as "a switching command is sent to the switching element." "Motor current" refers to the current flowing through the motor windings. "Dynamic braking current" refers to the current flowing through a dynamic braking resistor. Furthermore, the numerical examples given below are merely examples, and numerical values ​​other than those described here may also be used.

[0009] <Configuration of a Motor Drive Device According to an Embodiment of the Present Disclosure> FIG. 1 is a circuit diagram showing a motor drive device according to an embodiment of the present disclosure.

[0010] In the embodiment of the present disclosure described below, as an example, a case is shown in which a motor 3 is driven by a motor drive device 1 connected to an AC power source 2. The number of phases of the AC power source 2 is not particularly limited in each embodiment and each modified example, and may be, for example, three-phase or single-phase. Examples of the AC power source 2 include a three-phase 400V AC power source, a three-phase 200V AC power source, a three-phase 600V AC power source, and a single-phase 100V AC power source. Here, as an example, the AC power source 2 is three-phase. Furthermore, the number of motors 3 is not particularly limited in each embodiment, and may be multiple. When multiple motors 3 are provided, the inverter 11, the current detection unit 13, the overcurrent detection unit 14, the dynamic braking circuit 16, the switching command unit 17, and the dynamic braking command unit 18 are provided for each motor 3. Here, as an example, there is one motor 3. Machines in which the motor 3 is provided include, for example, machine tools and robots.

[0011] A motor drive device 1 according to an embodiment of the present disclosure includes a converter 10, an inverter 11, a capacitor 9, a U-phase power line 12U, a V-phase power line 12V, a W-phase power line 12W, a current detection unit 13, an overcurrent detection unit 14, a voltage detection unit 15, a dynamic braking circuit 16, a switching command unit 17, a dynamic braking command unit 18, a fault detection unit 19, and other circuits. Although not shown here, power lines that supply power to drive the current detection unit 13, the overcurrent detection unit 14, the voltage detection unit 15, the switching command unit 17, the dynamic braking command unit 18, and the fault detection unit 19 are provided in a system separate from the power line that supplies power from the AC power supply 2 to the converter 10.

[0012] The converter 10 converts AC power supplied from the AC power source 2 into DC power and outputs it to a DC link. In the example shown in FIG. 1 , the AC power source 2 is a three-phase AC power source, so the converter 10 is configured as a three-phase bridge circuit. If the AC power source 2 is a single-phase AC power source, the converter 10 is configured as a single-phase bridge circuit. Examples of the converter 10 include a diode rectifier, a PWM switching control rectifier, and a 120-degree conduction rectifier. For example, if the converter 10 is configured as a diode rectifier, it is configured as a three-phase bridge circuit of diodes. If the converter 10 is configured as a PWM switching control rectifier or a 120-degree conduction rectifier, it is configured as a three-phase bridge circuit of switching elements and diodes connected in reverse parallel to the switching elements. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used. An electromagnetic contactor, an AC reactor, an AC line filter, and the like may be provided on the AC input side of the converter 10, but these are not shown here.

[0013] A capacitor 9 is connected to the DC link between the converter 10 and the inverter 11. The capacitor 9 is sometimes referred to as a "DC link capacitor," "direct-current link capacitor," or "smoothing capacitor." The capacitor 9 has the function of suppressing oscillations in the DC output of the converter 10 and the function of storing DC power used by the inverter 11 to generate AC power. Examples of the capacitor 9 include an electrolytic capacitor and a film capacitor. A pre-charging circuit for pre-charging the capacitor 9 may be provided, but is not shown here.

[0014] An inverter 11 provided inside a servo amplifier (not shown) is connected to the converter 10 via a DC link. The inverter 11 is a three-phase bridge circuit in which a switching element is provided in each of the upper arms on the high-potential side and the lower arms on the low-potential side of each of the three phases. A diode is connected in antiparallel to each switching element. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used. In the illustrated example, for the U phase, a switching element S1 is provided in the upper arm and a switching element S2 is provided in the lower arm. For the V phase, a switching element S3 is provided in the upper arm and a switching element S4 is provided in the lower arm. For the W phase, a switching element S5 is provided in the upper arm and a switching element S6 is provided in the lower arm.

[0015] The inverter 11 receives on / off commands from the switching command unit 17 and turns on / off the switching elements S1, S2, S3, S4, S5, and S6, thereby converting the DC voltage in the DC link into an AC voltage for driving the motor and outputting this to the motor 3. As a result, the motor 3 is driven based on the AC voltage output from the inverter 11. Furthermore, the inverter 11 receives on / off commands from the switching command unit 17 and turns on / off the switching elements S1, S2, S3, S4, S5, and S6, thereby converting the AC voltage regenerated during deceleration of the motor 3 into a DC voltage and outputting this to the DC link.

[0016] The switching command unit 17 generates on / off commands for controlling the on / off operation of the switching elements S1, S2, S3, S4, S5, and S6 in the inverter 11 based on the rotational speed of the motor 3 (rotational speed feedback), the current flowing through the windings of the motor 3 (current feedback), the rotational speed command, the torque command, the position command, and the operation program of the motor 3. The on / off commands generated by the switching command unit 17 are transmitted to the switching elements S1, S2, S3, S4, S5, and S6. The power conversion operation of the inverter 11 is controlled by the drive commands generated by the switching command unit 17, thereby controlling the position, rotational speed, or torque of the rotor or rotating shaft of the motor 3. Note that the configuration of the switching command unit 17 defined here is merely an example, and the configuration of the switching command unit 17 may be defined by including terms such as a position command generation unit, a torque command generation unit, a current control unit, a position control unit, and a torque control unit.

[0017] U-phase power line 12U, V-phase power line 12V, and W-phase power line 12W are provided between the AC output side of inverter 11 and the input terminal of motor 3. Since inverter 11 is provided inside the servo amplifier, U-phase power line 12U, V-phase power line 12V, and W-phase power line 12W electrically connect the U-phase output terminal, V-phase output terminal, and W-phase output terminal of inverter 11 to the U-phase input terminal, V-phase input terminal, and W-phase input terminal of motor 3 via the terminals of the servo amplifier. U-phase power line 12U, V-phase power line 12V, and W-phase power line 12W each consist of a portion provided inside the servo amplifier and a portion provided outside the servo amplifier. U-phase power line 12U supplies the U-phase AC voltage output from the U-phase output terminal of inverter 11 to the U-phase input terminal of motor 3. V-phase power line 12V supplies the V-phase AC voltage output from the V-phase output terminal of inverter 11 to the V-phase input terminal of motor 3. W-phase power line 12W supplies the V-phase AC voltage output from the W-phase output terminal of inverter 11 to the W-phase input terminal of motor 3.

[0018] A current detection unit 13 is provided on the U-phase power line 12U, the V-phase power line 12V, and / or the W-phase power line 12W inside the servo amplifier. The current detection unit 13 includes, for example, a current sensor or a shunt resistor. The current detection unit 13 detects the values ​​of at least two of the three-phase currents output from the inverter 11 in the servo amplifier. In the example shown here, the current detection unit 13 detects the values ​​of the U-phase current and the V-phase current output from the inverter 11, for example.

[0019] The overcurrent detection unit 14 detects whether or not an overcurrent is flowing in the upper arm or the lower arm of each phase in the inverter 11. In the example shown here, as an example, the overcurrent detection unit 14 detects whether or not an overcurrent is flowing in the lower arm of each phase in the inverter 11.

[0020] The voltage detection unit 15 detects the value of the DC voltage, which is the potential difference between the positive potential appearing on the positive power line and the negative potential appearing on the negative power line in the DC link between the converter 10 and the inverter 11. The value of the DC voltage in the DC link detected by the voltage detection unit 15 corresponds to the voltage applied between the positive and negative terminals of the capacitor 9.

[0021] The dynamic braking circuit 16 is connected between the current detector 13 and the AC input terminals of the motor 3 in the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line 12W. The dynamic braking circuit 16 is provided inside or outside the inverter 11. The dynamic braking circuit 16 includes dynamic braking resistors 31U, 31V, and 31W and switches 32U, 32V, and 32W. The switches 32U, 32V, and 32W are formed by relays, switching elements, or the like.

[0022] As shown in the figure, a series circuit consisting of a dynamic braking resistor 31U and a switch 32U is connected between the U-phase current probe of the current detection unit 13 in the U-phase power line 12U and the U-phase AC input terminal of the motor 3. A series circuit consisting of a dynamic braking resistor 31V and a switch 32V is connected between the V-phase current probe of the current detection unit 13 in the V-phase power line 12V and the V-phase AC input terminal of the motor 3. A series circuit consisting of a dynamic braking resistor 31W and a switch 32W is connected between the W-phase current probe of the current detection unit 13 in the W-phase power line 12W and the W-phase AC input terminal of the motor 3. These series circuits are connected to each other in a Y connection (star connection). When the switches 32U, 32V, and 32W are closed, the three phases of the windings of the motor 3 are short-circuited via the dynamic braking resistors 31U, 31V, and 31W, respectively.

[0023] The switches 32U, 32V, and 32W are opened and closed in response to an open / close command generated by a dynamic braking command unit 18. When braking the motor 3 using the dynamic braking circuit 16, the switching command unit 17 outputs an OFF command to the switching elements S1, S2, S3, S4, S5, and S6 of the inverter 11, and the dynamic braking command unit 18 outputs a close command to the dynamic braking circuit 16. Upon receiving the OFF command, the inverter 11 stops outputting AC voltage. Upon receiving the close command, the dynamic braking command unit 18 closes the switches 32U, 32V, and 32W, shorting the input terminals of the motor 3 via the dynamic braking resistors 31U, 31V, and 31W. Even though the motor 3 is electrically disconnected from the power supply, a field magnetic flux exists, and the motor 3, rotating by inertia, functions as a generator, generating a dynamic braking current, which is a regenerative current. The regenerative current flows into dynamic brake resistors 31U, 31V, and 31W via the turned-on switches 32U, 32V, and 32W, and the regenerative power is converted into Joule heat and consumed in dynamic brake resistors 31U, 31V, and 31W. As a result, a deceleration torque is generated in motor 3. This deceleration torque brakes motor 3, and motor 3 coasts for a certain distance before finally coming to a stop.

[0024]

[0033] When there is no fault in any of the inverter 11, the power lines 12U, 12V, and 13W, and the dynamic braking circuit 16, the inverter 11 operates normally as described above in response to the on / off command from the switching command unit 17, and the dynamic braking circuit 16 operates normally as described above in response to the open / close command from the dynamic braking command unit 18.

[0025] However, if a fault occurs in any of the inverter 11, the power lines 12U, 12V, and 13W, or the dynamic braking circuit 16, the inverter 11 or the dynamic braking circuit 16 will not operate normally despite the on / off commands from the switching command unit 17 and the open / close commands from the dynamic braking command unit 18. Furthermore, the detection results from the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15 in the event of a fault will differ from the detection results in a normal state. Therefore, in one embodiment of the present disclosure, when the switching command unit 17 issues an on / off command and the dynamic braking command unit 18 issues an open / close command, the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15 obtain their detection results, and based on these, the presence or absence of a fault is detected, and if a fault is detected, the nature and location of the fault are identified.

[0026] Fault detection unit 19 detects faults in motor drive device 1 based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15 when switching command unit 17 commands the switching operation of each switching element S1, S2, S3, S4, S5, and S6 and when dynamic braking command unit 18 commands the opening and closing operation of each switch 32U, 32V, and 32W. Faults in motor drive device 1 that can be detected by fault detection unit 19 include open faults in switching elements S1, S2, S3, S4, S5, and S6, short circuits in switching elements S1, S2, S3, S4, S5, and S6, open faults in switches 32U, 32V, and 32W, short circuits in switches 32U, 32V, and 32W, breaks in power lines 12U, 12V, and 13W, short circuits in power lines 12U, 12V, and 13W, and ground faults in power lines 12U, 12V, and 13W. The fault detection unit 19 detects whether or not there is a fault in the motor drive device 1, and if there is a fault, it can identify the type and location of the fault.

[0027] The fault detection unit 19 includes a storage unit 21 , a calculation unit 22 , a comparison unit 23 , and a determination unit 24 .

[0028] In one embodiment of the present disclosure, there are seven types of command patterns, as will be described later, each of which is a combination of on / off commands for the switching operation of the switching elements S1, S2, S3, S4, S5, and S6 in the inverter 11 and open / close commands for the open / close operation of the switches 32U, 32V, and 32W in the dynamic braking circuit 16. When the switching elements S1, S2, S3, S4, S5, and S6 are switched and the switches 32U, 32V, and 32W are opened and closed in accordance with each command pattern, a detection result is obtained by the current detection unit 13 corresponding to the command pattern. The detection result by the current detection unit 13 corresponding to the command pattern depends on the presence or absence of a fault and the type and location of the fault. Therefore, in one embodiment of the present disclosure, a current reference value corresponding to each of the seven types of command patterns is used in the fault detection process to be able to determine the presence or absence of a fault and, if a fault exists, to be able to identify the type and location of the fault.

[0029] The current reference value corresponding to each of the seven types of command patterns is calculated according to a calculation formula corresponding to the command pattern. The calculation formula for calculating the current reference value corresponding to each of the seven types of command patterns is stored in the storage unit 21. The calculation formula corresponding to each command pattern will be described in detail later.

[0030] The calculation unit 22 calculates a current reference value corresponding to each command pattern according to a calculation formula stored in the memory unit 21, using the value of the DC voltage in the DC link detected by the voltage detection unit 15 when issuing commands to perform the switching operations of the switching elements S1, S2, S3, S4, S5, and S6 and to perform the opening and closing operations of the switches 32U, 32V, and 32W in accordance with each command pattern.

[0031] The comparison unit 23 compares the current value detected by the current detection unit 13 when instructing the switching operation of each switching element S1, S2, S3, S4, S5 and S6 and the opening and closing operation of each switch 32U, 32V and 32W in accordance with each command pattern with the current reference value corresponding to the command pattern calculated by the calculation unit 22.

[0032] The judgment unit 24 detects whether or not there is a fault based on the comparison results by the comparison unit 23 when the switching operations of each switching element S1, S2, S3, S4, S5 and S6 and the opening and closing operations of each switch 32U, 32V and 32W are instructed in accordance with the command pattern, and based on whether or not an overcurrent is detected by the overcurrent detection unit 14, and if there is a fault, determines the location and content of the fault.

[0033] As described above, the detection result by the voltage detection unit 15 used for the calculation processing by the calculation unit 22, the detection result by the current detection unit 13 used for the comparison processing by the comparison unit 23, and the detection result by the overcurrent detection unit 14 used for the judgment processing by the judgment unit 24 are obtained based on switching commands and opening / closing commands output at the same time.

[0034] The detection results by fault detection unit 19 are notified to an operator by a notification unit (not shown) such as a display device, audio device, or printer. Based on the detection results by fault detection unit 19 notified by the notification unit, the operator can quickly and reliably determine whether or not a fault has occurred within motor drive device 1, and if there is a fault, the content and location of the fault.

[0035] The display device indicates whether or not there is a fault, and if there is a fault, displays the nature and location of the fault within motor drive device 1. Examples of display devices include a standalone display monitor, a display monitor attached to motor drive device 1, a display monitor attached to a higher-level control device (not shown) that controls motor drive device 1, and a display monitor attached to a personal computer or mobile terminal. Alternatively, the display device may be configured with an illuminant such as an LED or lamp. For example, if there is no fault, the illuminant does not emit light, and if there is a fault, an illuminant provided corresponding to the nature and location of the fault may emit light.

[0036] For example, if there is no malfunction, the audio device does not emit a sound, but if there is a malfunction, the audio device emits a sound corresponding to the nature and location of the malfunction. Examples of audio devices include a speaker, a buzzer, and a chime. If there is a malfunction, the speaker may emit a sound indicating the nature and location of the malfunction, or the buzzer or chime may emit a sound of a tone corresponding to the nature and location of the malfunction.

[0037] If a malfunction occurs, the printer prints out the details of the malfunction, its location, and the date and time of occurrence on paper or the like.

[0038] The notification units exemplified above may be implemented in an appropriate combination. In addition, every time a fault detection result is obtained by the fault detection unit 19, it may be stored and accumulated in memory, and by creating a database, it may be useful for maintenance work, parts ordering work, etc.

[0039] The fault detection process by fault detection unit 19 may be started automatically, for example, when motor drive device 1 is started or stopped, or may be started by an operator operating an operation panel (not shown) attached to motor drive device 1. Furthermore, for example, the fault detection process by fault detection unit 19 may be started the next time motor drive device 1 is started after a fault is detected by fault detection unit 19. Furthermore, for example, the fault detection process by fault detection unit 19 may be started the next time motor drive device 1 is started after an alarm caused by a preset fault type to be detected this time is detected.

[0040] The motor drive device 1 includes at least one processor, which is an arithmetic processing device. Examples of the arithmetic processing device include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing device includes a current detection unit 13, an overcurrent detection unit 14, a voltage detection unit 15, a switching command unit 17, a dynamic braking command unit 18, a fault detection unit 19, and other processing units. Each of these units included in the arithmetic processing device is a functional module implemented by, for example, a program executed on the processor. For example, if the current detection unit 13, the overcurrent detection unit 14, the voltage detection unit 15, the switching command unit 17, the dynamic braking command unit 18, the fault detection unit 19, and other processing units are implemented in the form of a program, the functions of each unit can be realized by operating the arithmetic processing device in accordance with the program. The programs for executing the processes in the current detection unit 13, the overcurrent detection unit 14, the voltage detection unit 15, the switching command unit 17, the dynamic braking command unit 18, the fault detection unit 19, and other processing units may be provided in the form of being recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the current detection unit 13, the overcurrent detection unit 14, the voltage detection unit 15, the switching command unit 17, the dynamic braking command unit 18, the fault detection unit 19, and other processing units may be realized as semiconductor integrated circuits into which programs for realizing the functions of the respective units are written.

[0041] The motor drive device 1 also includes at least one memory serving as a storage device. The memory includes the current detection unit 13, the overcurrent detection unit 14, the voltage detection unit 15, the switching command unit 17, the dynamic braking command unit 18, the fault detection unit 19, and various other storage units within the processing units. Examples of the memory include electrically erasable and recordable nonvolatile memory such as an EEPROM (registered trademark), or high-speed read / write random access memory such as a DRAM or an SRAM. The storage unit may also include a hard disk drive (HDD) or a solid state drive (SSD). The memory stores programs for operating the current detection unit 13, the overcurrent detection unit 14, the voltage detection unit 15, the switching command unit 17, the dynamic braking command unit 18, the fault detection unit 19, and the other processing units. The memory also stores the value of the current output from the inverter 11 detected by the current detection unit 13. The memory also stores information regarding the presence or absence of an overcurrent detected by the overcurrent detection unit 14. The memory stores the value of the DC voltage in the DC link detected by the voltage detection unit 15. The memory stores a calculation formula for calculating a current reference value. The current reference value calculated by the calculation unit 22, the comparison result by the comparison unit 23, and the determination result by the determination unit 24 are stored. The memory stores information on seven types of command patterns. The memory stores various programs and various data related to the switching command unit 17. The memory stores various programs and various data related to the dynamic braking command unit 18. The memory stores various programs and various data related to the motor drive device 1.

[0042] <Command Patterns> In one embodiment of the present disclosure, there are seven types of command patterns each consisting of a combination of ON / OFF commands for the switching operations of the switching elements S1, S2, S3, S4, S5, and S6 in the inverter 11 and open / close commands for the open / close operations of the switches 32U, 32V, and 32W in the dynamic braking circuit 16.

[0043] Each of the seven types of command patterns includes information regarding on commands and off commands for each switching element S1, S2, S3, S4, S5 and S6, information regarding the length of time for which on commands are output to each switching element S1, S2, S3, S4, S5 and S6, and information regarding open commands and close commands for each switch 32U, 32V and 32W.

[0044] FIG. 2 is a diagram illustrating an example of a command pattern according to an embodiment of the present disclosure.

[0045] Of the seven types of command patterns, the first command pattern Q1, the second command pattern Q2, and the third command pattern Q3 each include an ON command for a switching element provided in one phase of the upper arm and an OFF command for a switching element provided in two phases other than the one phase, an ON command for a switching element provided in two phases of the lower arm and an OFF command for a switching element provided in one phase other than the two phases, information about the length of time for which the ON command is output, and a close command for each of the switches 32U, 32V, and 32W. Specifically, this is as follows.

[0046] The combinations of ON / OFF commands and opening / closing commands in command pattern Q1 are as follows. That is, in command pattern Q1, the switching command unit 17 outputs ON commands to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. However, in command pattern Q1, the time during which ON commands are output from the switching command unit 17 to the switching elements S1, S4, and S6 is "short" (e.g., several tens of microseconds) so that no motor current flows through the motor 3 during the ON command. During time periods other than when the ON commands are output, the switching command unit 17 also outputs OFF commands to the switching elements S1, S4, and S6. Note that the "time during which ON commands are output" for command pattern Q1 and command patterns Q2 to Q7, which will be described later, will be described in detail later. Furthermore, while following command pattern Q1, the switching command unit 17 always outputs OFF commands to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 always outputs a close command to each of the switches 32U, 32V, and 32W while following the command pattern Q1.

[0047] The combinations of ON / OFF commands and open / close commands for command pattern Q2 are as follows. That is, in command pattern Q2, switching command unit 17 outputs ON commands to U-phase lower arm switching element S2, V-phase upper arm switching element S3, and W-phase lower arm switching element S6. However, in command pattern Q2, the ON commands are output from switching command unit 17 to switching elements S2, S3, and S6 for a "short time" (e.g., several tens of microseconds) long enough that no motor current flows through motor 3 during the ON commands. During times other than the ON commands, switching command unit 17 also outputs OFF commands to switching elements S2, S3, and S6. Furthermore, while command pattern Q2 is being followed, switching command unit 17 always outputs OFF commands to U-phase upper arm switching element S1, V-phase lower arm switching element S4, and W-phase upper arm switching element S5. Furthermore, while command pattern Q2 is being followed, dynamic braking command unit 18 always outputs close commands to switches 32U, 32V, and 32W.

[0048] The combinations of ON / OFF commands and open / close commands for command pattern Q3 are as follows: That is, in command pattern Q3, switching command unit 17 outputs ON commands to U-phase lower arm switching element S2, V-phase lower arm switching element S4, and W-phase upper arm switching element S5. However, in command pattern Q3, the ON commands are output from switching command unit 17 to switching elements S2, S4, and S5 for a "short time" (e.g., several tens of microseconds) long enough that no motor current flows through motor 3 during the ON commands. During times other than when the ON commands are output, switching command unit 17 also outputs OFF commands to switching elements S2, S4, and S5. Furthermore, while command pattern Q3 is being followed, switching command unit 17 always outputs OFF commands to U-phase upper arm switching element S1, V-phase upper arm switching element S3, and W-phase lower arm switching element S6. Furthermore, while command pattern Q3 is being followed, dynamic braking command unit 18 always outputs close commands to switches 32U, 32V, and 32W.

[0049] Of the seven types of command patterns, the fourth command pattern Q4 and the fifth command pattern Q5 each include an ON command for the switching elements provided in two phases of the upper arm and an OFF command for the switching elements provided in one phase other than the two phases, an ON command for the switching elements provided in one phase of the lower arm and an OFF command for the switching elements provided in two phases other than the one phase, information regarding the length of time for which the ON commands are output, and an open command for each of the switches 32U, 32V, and 32W. Specifically, this is as follows.

[0050] The combinations of ON / OFF commands and open / close commands for command pattern Q4 are as follows: That is, in command pattern Q4, switching command unit 17 outputs ON commands to U-phase upper arm switching element S1, V-phase upper arm switching element S3, and W-phase lower arm switching element S6. However, in command pattern Q4, the ON commands are output from switching command unit 17 to switching elements S1, S3, and S6 for a "short time" (e.g., several tens of microseconds) long enough that no motor current flows through motor 3 during the ON commands. During times other than when the ON commands are output, switching command unit 17 also outputs OFF commands to switching elements S1, S3, and S6. Furthermore, while command pattern Q4 is being followed, switching command unit 17 always outputs OFF commands to U-phase lower arm switching element S2, V-phase lower arm switching element S4, and W-phase upper arm switching element S5. Furthermore, while command pattern Q4 is being followed, dynamic braking command unit 18 always outputs open commands to switches 32U, 32V, and 32W.

[0051] The combinations of ON / OFF commands and open / close commands for command pattern Q5 are as follows: That is, in command pattern Q5, switching command unit 17 outputs ON commands to U-phase upper arm switching element S1, V-phase lower arm switching element S4, and W-phase upper arm switching element S5. However, in command pattern Q4, the ON commands are output from switching command unit 17 to switching elements S1, S4, and S5 for a "short time" (e.g., several tens of microseconds) long enough that no motor current flows through motor 3 during the ON commands. During times other than the ON commands, switching command unit 17 also outputs OFF commands to switching elements S1, S4, and S5. Furthermore, while command pattern Q5 is being followed, switching command unit 17 always outputs OFF commands to U-phase lower arm switching element S2, V-phase upper arm switching element S3, and W-phase lower arm switching element S6. Furthermore, while command pattern Q5 is being followed, dynamic braking command unit 18 always outputs open commands to switches 32U, 32V, and 32W.

[0052] Of the seven command patterns, a sixth command pattern Q6 and a seventh command pattern Q7 each include an ON command for a switching element provided in two phases of the upper arm and an OFF command for a switching element provided in one phase other than the two phases, an ON command for a switching element provided in one phase of the lower arm and an OFF command for a switching element provided in two phases other than the one phase, information about the length of time for outputting the ON command, and an open command for each of the switches. The length of time for outputting the ON command in each of the command pattern Q6 and the command pattern Q7 is long enough for a motor current to flow through the motor 3, i.e., is set to a value longer than the length of time for outputting the ON command in each of the command patterns Q1 to Q5.

[0053] The combinations of ON / OFF commands and open / close commands for command pattern Q6 are as follows: That is, in command pattern Q6, switching command unit 17 outputs ON commands to U-phase upper arm switching element S1, V-phase upper arm switching element S3, and W-phase lower arm switching element S6. However, in command pattern Q6, the ON commands are output from switching command unit 17 to switching elements S1, S3, and S6 for a "long time" (e.g., several tens of milliseconds) long enough for motor current to flow through motor 3 during the ON command. During time periods other than the ON commands, switching command unit 17 also outputs OFF commands to switching elements S1, S3, and S6. Furthermore, while command pattern Q6 is being followed, switching command unit 17 always outputs OFF commands to U-phase lower arm switching element S2, V-phase lower arm switching element S4, and W-phase upper arm switching element S5. Furthermore, while command pattern Q6 is being followed, dynamic braking command unit 18 always outputs open commands to switches 32U, 32V, and 32W.

[0054] The combinations of ON / OFF commands and open / close commands for command pattern Q7 are as follows: That is, in command pattern Q7, switching command unit 17 outputs ON commands to U-phase upper arm switching element S1, V-phase lower arm switching element S4, and W-phase upper arm switching element S5. However, in command pattern Q7, the ON commands are output from switching command unit 17 to switching elements S1, S4, and S5 for a "long time" (e.g., several tens of milliseconds) long enough for motor current to flow through motor 3 during the ON command. During time periods other than the ON commands, switching command unit 17 also outputs OFF commands to switching elements S1, S4, and S5. Furthermore, while command pattern Q7 is being followed, switching command unit 17 always outputs OFF commands to U-phase lower arm switching element S2, V-phase upper arm switching element S3, and W-phase lower arm switching element S6. Furthermore, while command pattern Q7 is being followed, dynamic braking command unit 18 always outputs open commands to switches 32U, 32V, and 32W.

[0055] <Time for which an ON command is output in a command pattern> As described above, the time for which an ON command is output by the switching command unit 17 is set to a "short time" (e.g., several tens of microseconds) for command patterns Q1 to Q5 such that no motor current flows through the motor 3 during the ON command. Also, for command patterns Q6 and Q7, it is set to a "long time" (e.g., several tens of milliseconds) such that motor current flows through the motor 3 during the ON command. The length of time for which an ON command is output in each of command patterns Q6 and Q7 is set to a value longer than the length of time for which an ON command is output in each of command patterns Q1 to Q5. The time for which an ON command is output in a command pattern will be described in more detail below with reference to FIGS. 3 to 6B.

[0056] FIG. 3 is a circuit diagram illustrating an example of a current path when one-phase switching element of the upper arm and two-phase switching elements of the lower arm are in an ON state and three switches in the dynamic braking circuit are closed.

[0057] 3 does not illustrate the AC power supply 2, converter 10, current detection unit 13, overcurrent detection unit 14, voltage detection unit 15, switching command unit 17, dynamic braking command unit 18, and fault detection unit 19. On the other hand, the motor resistance 61U and motor coil 62U of the U-phase winding of the motor 3, the motor resistance 61V and motor coil 62V of the V-phase winding of the motor 3, and the motor resistance 61U and motor coil 62W of the W-phase winding of the motor 3 are shown.

[0058] The equivalent circuit when the upper-arm switching element for one phase and the lower-arm switching elements for two phases different from the one phase are turned on is the same as the equivalent circuit when the upper-arm switching elements for the two phases and the lower-arm switching elements for the two phases different from the one phase are turned on. Thus, the example shown in FIG. 3 illustrates a case where the upper-arm switching element S1 for the U phase, the lower-arm switching element S4 for the V phase, and the lower-arm switching element S6 for the W phase in the inverter 11 are turned on. The reference symbols of the switching elements that are turned on are indicated by open circles. Furthermore, the three switches 32U, 32V, and 32W in the dynamic braking circuit 16 are closed.

[0059] For the U phase, the U phase current flowing out from the DC link via switching element S1 is separated into a motor current flowing through motor resistor 61U and motor coil 62U and a dynamic braking current flowing through dynamic braking resistor 31U and switch 32U. For the V phase, the V phase current flowing into the DC link via switching element S4 is a combination of a motor current flowing through motor resistor 61V and motor coil 62V and a dynamic braking current flowing through dynamic braking resistor 31V and switch 32V. For the W phase, the W phase current flowing into the DC link via switching element S6 is a combination of a motor current flowing through motor resistor 61W and motor coil 62W and a dynamic braking current flowing through dynamic braking resistor 31W and switch 32W.

[0060] Fig. 4A is a circuit diagram showing an equivalent circuit of the current path shown in Fig. 3. In Fig. 4A, the switches 32U, 32V, and 32W and the capacitor 9 shown in Fig. 3 are omitted.

[0061] In FIG. 4A, the resistance values ​​of the dynamic braking resistors 31U, 31V, and 31W are R DB [Ω], and the resistance value of each of the motor resistors 61U, 61V, and 61W is R M The inductance values ​​of the motor coils 62U, 62V, and 62W are set to L M [H]. The voltage of the capacitor 9 (i.e., the DC voltage in the DC link) is set to V DC It is set to [V].

[0062] U-phase current I output from inverter 11 U [A] is the dynamic braking current I flowing through the dynamic braking resistor 31U. UDB [A] and the motor current I flowing through the motor resistor 61U and the motor coil 62U UM Dynamic braking current I UDB [A] is the dynamic braking current I flowing through the dynamic braking resistor 31V VDB [A] and the dynamic braking current I flowing through the dynamic braking resistor 31W WDB [A] and the motor current I UM [A] is the motor current I flowing through the motor resistor 61V and the motor coil 62V. VM [A] and the motor current I flowing through the motor resistor 61W and the motor coil 62W WM Dynamic braking current I VDB [A] and motor current I VM [A] is added to form the V-phase current I V The dynamic braking current I WDB [A] and motor current I WM [A] is combined to form the W-phase current I W It flows into the inverter 11 as [A].

[0063] FIG. 4B is a circuit diagram showing a case where the impedances of the equivalent circuit shown in FIG. 4A are combined.

[0064] The resistance value of the combined resistance 31 of the dynamic brake resistors 31U, 31V and 31W is 3R DB The resistance value of the combined resistance 61 of the motor resistors 61U, 61V and 61W is 3R M The inductance value of the combined inductance 62 of the motor coils 62U, 62V, and 62W is 3L M / 2[H].

[0065] From Kirchhoff's first law, Equation 1 holds.

[0066]

[0067] Dynamic braking current I UDB [A] can be expressed as in Equation 2.

[0068]

[0069] According to the circuit equation for a general RL series circuit, the motor current I UM [A] can be expressed as in Equation 3. In Equation 3, t [s] represents the time of the ON operation of the switching element. The ON operation of the switching element starts at time t=0 [s].

[0070]

[0071] When the time t [s] of the ON operation of the switching element commanded to be ON is very short, the motor current I UM [A] is the dynamic braking current I UDB [A], the U-phase current I output from the inverter 11 U [A] is expressed as in Equation 4.

[0072]

[0073] If the time of the ON command to the switching elements is very short, the ON operation time t [s] of the switching elements will also be very short, and therefore, according to Equation 4, no current will flow through the combined resistance 61 of the motor resistances of the motor 3 and the combined inductance 62 of the motor coils. The "short time" during which no motor current flows through the motor 3 between ON commands to the switching elements in command patterns Q1 to Q5 is the time t [s] for which Equation 4 is valid. As an example, this is about several tens of microseconds, but other values ​​are also possible.

[0074] FIG. 5 is a circuit diagram illustrating an example of a current path when one phase switching element of the upper arm and two phase switching elements of the lower arm are in an ON state and three switches in the dynamic braking circuit are open.

[0075] 5 does not illustrate the AC power supply 2, converter 10, current detection unit 13, overcurrent detection unit 14, voltage detection unit 15, switching command unit 17, dynamic braking command unit 18, and fault detection unit 19. On the other hand, the motor resistance 61U and motor coil 62U of the U-phase winding of the motor 3, the motor resistance 61V and motor coil 62V of the V-phase winding of the motor 3, and the motor resistance 61U and motor coil 62W of the W-phase winding of the motor 3 are shown.

[0076] 5 illustrates an example in which the U-phase upper-arm switching element S1, the V-phase lower-arm switching element S4, and the W-phase lower-arm switching element S6 in the inverter 11 are turned on. The reference symbols of the switching elements that are turned on are marked with white circles. In addition, the three switches 32U, 32V, and 32W in the dynamic braking circuit 16 are open.

[0077] For the U phase, the U-phase current flowing out from the DC link via switching element S1 flows through the dynamic braking resistor 31U and switch 32U. For the V phase, the current flowing through the dynamic braking resistor 31V and switch 32V flows into the DC link via switching element S4 as a V-phase current. For the W phase, the current flowing through the dynamic braking resistor 31W and switch 32W flows into the DC link via switching element S6 as a W-phase current. Because switches 32U, 32V, and 32W are open, no dynamic braking current flows through the dynamic braking resistors 31U, 31V, and 31W.

[0078] Fig. 6A is a circuit diagram showing an equivalent circuit of the current path shown in Fig. 5. In Fig. 6A, the switches 32U, 32V, and 32W and the capacitor 9 shown in Fig. 5 are omitted.

[0079] In FIG. 6A, the resistance values ​​of the motor resistors 61U, 61V, and 61W are R M [Ω], and the inductance value of each of the motor coils 62U, 62V, and 62W is L M [H]. The voltage of the capacitor 9 (i.e., the DC voltage in the DC link) is set to V DC It is set to [V].

[0080] U-phase current I output from inverter 11 U [A] is the motor current I UM The motor current I [A] flows through the motor resistor 61U and the motor coil 62U. UM [A] is the motor current I flowing through the motor resistor 61V and the motor coil 62V. VM [A], and the motor current I flowing through the motor resistor 61W and the motor coil 62W. WM [A] and the motor current I VM [A] is the V-phase current I V The motor current I WM [A] is the W-phase current I W It flows into the inverter 11 as [A].

[0081] FIG. 6B is a circuit diagram showing a case where the impedances of the equivalent circuit shown in FIG. 6A are combined.

[0082] The resistance value of the combined resistance 61 of the motor resistors 61U, 61V and 61W is 3R M The inductance value of the combined inductance 62 of the motor coils 62U, 62V, and 62W is 3L M / 2[H].

[0083] According to the circuit equation of a general RL series circuit, the U-phase current I U [A] can be expressed as in Equation 5. In Equation 5, t [s] represents the time of the ON operation of the switching element, and the ON operation of the switching element starts at time t=0 [s].

[0084]

[0085] Since the switches 32U, 32V, and 32W are open, the U-phase current I U Current [A] flows through a combined resistance 61 of the motor resistance of the motor 3 and a combined inductance 62 of the motor coil. The "long time" during which motor current flows through the motor 3 between the ON commands to the switching elements in command pattern Q6 and command pattern Q7 is a time t [s] that allows current flow to be detected with sufficient detection accuracy by the current detection unit 13. As an example, this is about several tens of milliseconds, but other values ​​are also possible.

[0086] <State Determination Process by Comparator and Determinator for Each Command Pattern> In one embodiment of the present disclosure, the state determination process described below is executed. The determiner 24 checks the determination result of the state determination process against the fault determination conditions described below to detect the presence or absence of a fault, and if there is a fault, identifies the content and location of the fault.

[0087] In the state determination process, the comparison unit 23 compares the current reference value with the detection result by the current detection unit 13 for each of the command patterns Q1 to Q7, and the determination unit 24 executes a state determination process for each of the command patterns Q1 to Q7 to determine the state of the motor drive device 1 to which the command pattern is commanded, based on the comparison result by the comparison unit 23 and whether or not an overcurrent has been detected by the overcurrent detection unit 14.

[0088] When switching command unit 17 outputs an on / off command and dynamic brake command unit 18 outputs an open / close command in accordance with a certain command pattern, the detection result by current detection unit 13 and the result by overcurrent detection unit 14 will differ depending on whether motor drive device 1 is currently in one of the following states: (1) normal, (2) an open fault in switching element S1, S2, S3, S4, S5, or S6, (3) a short circuit in switching element S1, S2, S3, S4, S5, or S6, (4) an open fault in switches 32U, 32V, and / or 32W, (5) a short circuit in switches 32U, 32V, and / or 32W, (6) a break in power lines 12U, 12V, and / or 13W, (7) a short circuit in power lines 12U, 12V, and / or 13W, or (8) a ground fault in power line 12U, 12V, or 13W. In the state determination process by the determination unit 24, the detection results by the current detection unit 13 and the detection results by the overcurrent detection unit 14 are compared with the determination criteria tables shown in Figures 7 to 13 for each command pattern Q1 to Q7 to determine the current state of the motor drive device.

[0089] 7 to 13 are composed of the current reference value of the U-phase current, the current reference value of the V-phase current, and the presence or absence of an overcurrent. The current reference value of the U-phase current and the current reference value of the V-phase current for each of the command patterns Q1 to Q7 are calculated by the calculation unit 22. That is, the calculation unit 22 calculates the value V of the DC voltage in the DC link detected by the voltage detection unit 15 when the switching operations of the switching elements S1, S2, S3, S4, S5, and S6 and the opening and closing operations of the switches 32U, 32V, and 32W are instructed in accordance with the command pattern. DC [V] is used to calculate the current reference value of the U-phase current and the current reference value of the V-phase current corresponding to the command pattern in accordance with the calculation formula stored in the storage unit 21.DB [Ω] is the resistance value of each of the dynamic braking resistors 31U, 31V, and 31W.

[0090] FIG. 7 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in the command pattern Q1 used in the state determination process by the determination unit, and the state of the motor drive device.

[0091] The determination criteria table shown in FIG. 7 shows states A1 to G1 that are determined based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs a close command in accordance with command pattern Q1.

[0092] In the state A1, the value of the U-phase current detected by the current detection unit 13 is "V DC / ((3R DB ) / 2) and the value of the V-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2" is the case.

[0093] State B1 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0094] In the state C1, the value of the U-phase current detected by the current detection unit 13 is "V DC / (2R DB ) and the value of the V-phase current detected by the current detection unit 13 is "0".

[0095] In the state D1, the value of the U-phase current detected by the current detection unit 13 is "V DC / (2R DB ) and the value of the V-phase current detected by the current detection unit 13 is "-V DC / (2R DB )" is the case.

[0096] In the state E1, the value of the U-phase current detected by the current detection unit 13 is "V DC / ((3R DB) / 2) is greater than "-V DC / ((3R DB ) / 2) / 2 is smaller than ".

[0097] In the state F1, the value of the U-phase current detected by the current detection unit 13 is "V DC / ((3R DB ) / 2) is greater than "-V DC / ((3R DB ) / 2) / 2 or more" is the case.

[0098] State G1 corresponds to a case where the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "0".

[0099] FIG. 8 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in the command pattern Q2 used in the state determination process by the determination unit, and the state of the motor drive device.

[0100] The judgment criteria table shown in FIG. 8 shows states A2 to G2 that are judged based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs a close command in accordance with command pattern Q2.

[0101] In the state A2, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2", and the value of the V-phase current detected by the current detection unit 13 is "V DC / ((3R DB ) / 2) is applicable.

[0102] State B2 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0103] In the state C2, the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "V DC / (2R DB )" is the case.

[0104] In the state D2, the value of the U-phase current detected by the current detection unit 13 is "-V DC / (2R DB ) and the value of the V-phase current detected by the current detection unit 13 is "V DC / (2R DB )" is the case.

[0105] In the state E2, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2”, and the value of the V-phase current detected by the current detection unit 13 is “V DC / ((3R DB ) / 2) is greater than.

[0106] In the state F2, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2 or more”, and the value of the V-phase current detected by the current detection unit 13 is “V DC / ((3R DB ) / 2) is greater than.

[0107] State G2 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and the overcurrent detection unit 14 detects that "an overcurrent exists".

[0108] FIG. 9 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in the command pattern Q3 used in the state determination process by the determination unit, and the state of the motor drive device.

[0109] The judgment criteria table shown in FIG. 9 shows states A3 to H3 that are judged based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs a close command in accordance with command pattern Q3.

[0110] In the state A3, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2", and the value of the V-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2" is applicable.

[0111] State B3 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0112] In state C3, the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "-V DC / (2R DB )" is the case.

[0113] In the state D3, the value of the U-phase current detected by the current detection unit 13 is "-V DC / (2R DB ) and the value of the V-phase current detected by the current detection unit 13 is "0").

[0114] In the state E3, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2 or more”, and the value of the V-phase current detected by the current detection unit 13 is “−V DC / ((3R DB ) / 2) / 2 is smaller than ".

[0115] In the state F3, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB) / 2) / 2”, and the value of the V-phase current detected by the current detection unit 13 is “-V DC / ((3R DB ) / 2) / 2" is the case.

[0116] State G3 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "0".

[0117] In the state H3, the value of the U-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) / 2”, and the value of the V-phase current detected by the current detection unit 13 is “-V DC / ((3R DB ) / 2) / 2 is smaller than ".

[0118] FIG. 10 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in command pattern Q4 used in the state determination process by the determination unit, and the state of the motor drive device.

[0119] The determination criteria table shown in FIG. 10 shows states A4 to F4 that are determined based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs an open command in accordance with command pattern Q4.

[0120] State A4 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0121] In the state B4, the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "V DC / (2R DB )" is the case.

[0122] In state C4, the value of the U-phase current detected by the current detection unit 13 is "V DC / (2R DB) and the value of the V-phase current detected by the current detection unit 13 is "0").

[0123] State D4 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "greater than 0" and the value of the V-phase current detected by the current detection unit 13 is "0".

[0124] State E4 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "greater than 0."

[0125] In the state F4, the value of the U-phase current detected by the current detection unit 13 is "V DC / ((3R DB ) / 2) / 2", and the value of the V-phase current detected by the current detection unit 13 is "V DC / ((3R DB ) / 2) / 2" is the case.

[0126] FIG. 11 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in command pattern Q5 used in the state determination process by the determination unit, and the state of the motor drive device.

[0127] The determination criteria table shown in FIG. 11 shows states A5 to E5 that are determined based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs an open command in accordance with command pattern Q5.

[0128] State A5 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0129] In the state B5, the value of the U-phase current detected by the current detection unit 13 is "V DC / (2R DB ) and the value of the V-phase current detected by the current detection unit 13 is "-V DC / (2R DB )" is the case.

[0130] In the state C5, the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "-V DC / (2R DB )" is the case.

[0131] State D5 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "greater than 0" and the value of the V-phase current detected by the current detection unit 13 is "0".

[0132] In the state E5, the value of the U-phase current detected by the current detection unit 13 is “V DC / ((3R DB ) / 2) / 2", and the value of the V-phase current detected by the current detection unit 13 is "-V DC / ((3R DB ) / 2) is the case.

[0133] FIG. 12 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in command pattern Q6 used in the state determination process by the determination unit, and the state of the motor drive device.

[0134] The determination criteria table shown in FIG. 12 shows states A6 to D6 that are determined based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs an open command in accordance with command pattern Q6.

[0135] State A6 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "greater than 0" and the value of the V-phase current detected by the current detection unit 13 is "greater than 0".

[0136] State B6 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "greater than 0."

[0137] State C6 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "greater than 0" and the value of the V-phase current detected by the current detection unit 13 is "0".

[0138] State D6 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0139] FIG. 13 is a diagram showing a determination criteria table showing the relationship between the combination of the current reference value and the presence or absence of an overcurrent in the command pattern Q7 used in the state determination process by the determination unit, and the state of the motor drive device.

[0140] The judgment criteria table shown in FIG. 13 shows states A7 to D7 that are judged based on the detection results by the current detection unit 13 and the overcurrent detection unit 14 when the switching command unit 17 outputs an on / off command and the dynamic brake command unit 18 outputs an open command in accordance with command pattern Q7.

[0141] State A7 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "greater than 0" and the value of the V-phase current detected by the current detection unit 13 is "less than 0".

[0142] State B7 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0" and the value of the V-phase current detected by the current detection unit 13 is "less than 0".

[0143] State C7 corresponds to the case where the value of the U-phase current detected by the current detection unit 13 is "0", the value of the V-phase current detected by the current detection unit 13 is "0", and "no overcurrent" is detected by the overcurrent detection unit 14.

[0144] 1 shows a case where overcurrent detection unit 14 is configured to detect the presence or absence of an overcurrent flowing in the lower arm of each phase in inverter 11. Even when overcurrent detection unit 14 is configured to detect the presence or absence of an overcurrent flowing in the upper arm of each phase in inverter 11, the relationship between the combination of the current reference value and the presence or absence of an overcurrent in each command pattern, and the state of the motor drive device shown in the state reference tables of FIGS.

[0145] Furthermore, when comparing the current reference values ​​in each command pattern shown in the state reference tables of Figures 7 to 13 with the detection results by the current detection unit 13, a certain degree of margin may be provided for each current reference value in the state reference table, taking into account the detection accuracy of the current detection unit 13.

[0146] <Fault detection process using fault determination conditions by determination unit> The determination unit 24 determines the current state of the motor drive device 1 by state determination process based on the state reference tables in Figures 7 to 13, and then checks the determination result in the state determination process against the fault determination conditions shown in Figure 14 to detect whether or not a fault exists, and if a fault exists, identifies the content and location of the fault. The fault detection process by the determination unit 24 using the fault determination conditions will be described below.

[0147] Fig. 14 is a diagram showing the fault determination conditions used in the fault detection process by the determination unit. The fault determination conditions shown in Fig. 14 show a combination of information about the state of the motor drive device 1 that is necessary for detecting the presence or absence of a fault and for identifying the content and location of the fault. Only the states shown in Fig. 14 are involved in detecting the presence or absence of a fault and for identifying the content and location of the fault. On the other hand, states that are not involved in detecting the presence or absence of a fault and for identifying the content and location of the fault are indicated by "-" in Fig. 14.

[0148] The switching element S1 of the upper arm of the U phase is determined to have an open circuit fault when the motor drive device 1 is in state B1 or state A2.

[0149] An open fault is determined to have occurred in switching element S2 of the lower arm of the U phase when motor drive device 1 is in state A1 or state C2.

[0150] An open circuit fault is determined to have occurred in switching element S3 of the upper arm of the V phase when motor drive device 1 is in state A1 or state B2.

[0151] An open fault is determined to have occurred in switching element S4 of the lower arm of the V-phase when motor drive device 1 is in state C1 or state A2.

[0152] An open fault is determined to have occurred in switching element S5 of the upper arm of the W phase when motor drive device 1 is in state A1, state A2, or state B3.

[0153] An open fault is determined to have occurred in the switching element S6 of the lower arm of the W phase when the motor drive device 1 is in state D1, state D2, or state A3.

[0154] The switching element S1 of the upper arm of the U phase is determined to be short-circuited when the motor drive device 1 is in state A1, state G2, or state G3.

[0155] The switching element S2 of the lower arm of the U phase is determined to be short-circuited when the motor drive device 1 is in state G1, state A2, or state A3.

[0156] It is determined that switching element S3 of the upper arm of the V-phase is short-circuited when motor drive device 1 is in state G1, state G2, or state G3.

[0157] It is determined that switching element S4 of the lower arm of the V-phase is short-circuited when motor drive device 1 is in state A1, state G2, or state A3.

[0158] The switching element S5 of the upper arm of the W phase is determined to be short-circuited when the motor drive device 1 is in state G1, G2, or state A3.

[0159] The switching element S6 of the lower arm of the W phase is determined to be short-circuited when the motor drive device 1 is in state A1, state A2, or state G3.

[0160] An open circuit fault is determined to have occurred in the switches of two or more phases of the dynamic braking circuit 16 (an open circuit fault in the switches 32U and 32V, an open circuit fault in the switches 32V and 32W, an open circuit fault in the switches 32W and 32U, or an open circuit fault in the switches 32U, 32V, and 32W) when the motor drive device 1 is in state B1 or state B2.

[0161] The U-phase switch 32U of the dynamic braking circuit 16 is determined to have an open fault when the motor drive device 1 is in state B1 or state C2.

[0162] An open fault is determined to have occurred in the V-phase switch 32V of the dynamic braking circuit 16 when the motor drive device 1 is in state C1 or state B2.

[0163] The W-phase switch 32W of the dynamic braking circuit 16 is determined to have an open fault when the motor drive device 1 is in state D1, state D2, or state B3.

[0164] The U-phase switch 32U and the V-phase switch 32V of the dynamic braking circuit 16 are determined to be short-circuited when the motor drive device 1 is in state A4 or state B5.

[0165] The V-phase switch 32V and the W-phase switch 32W of the dynamic braking circuit 16 are determined to be short-circuited when the motor drive device 1 is in state B4.

[0166] The W-phase switch 32W and the U-phase switch 32U of the dynamic braking circuit 16 are determined to be short-circuited when the motor drive device 1 is in state C4.

[0167] The switches 32U, 32V, and 32W for all three phases of the dynamic braking circuit 16 are determined to be short-circuited when the motor drive device 1 is in state F4.

[0168] Note that, because the state in which a short circuit occurs in the switches 32U, 32V, and / or 32W of the dynamic braking circuit 16 is identical to the state of the switches 32U, 32V, and / or 32W resulting from a close command issued by the dynamic braking command unit 18 under the command patterns Q1 to Q3, it is not necessary to use the state determination results under the command patterns Q1 to Q3 to detect a short circuit in the switches 32U, 32V, and / or 32W of the dynamic braking circuit 16.

[0169] The U-phase power line 12U is determined to be broken when the motor drive device 1 is in state A4, state A5, or state B6.

[0170] A break in the V-phase power line 12V is determined when the motor drive device 1 is in state A4, state A5, or state C6.

[0171] The W-phase power line 12W is determined to be broken when the motor drive device 1 is in state A4, state A5, state A6, or state A7.

[0172] Two or more of the U-phase power line 12U, V-phase power line 12V, and W-phase power line 12W are determined to be disconnected when the motor drive device 1 is in state A4, state A5, state D6, or state C7.

[0173] In command patterns Q1 to Q3, for a "short time" (e.g., several tens of microseconds) during an ON command, no motor current flows through motor 3. Therefore, a state in which a break occurs in U-phase power line 12U, V-phase power line 12V, and / or W-phase power line 12W is the same as the state of motor drive device 1 under command patterns Q1 to Q3, and therefore, the state determination results under command patterns Q1 to Q3 do not need to be used to detect breaks in U-phase power line 12U, V-phase power line 12V, and / or W-phase power line 12W.

[0174] A short circuit between U-phase power line 12U and V-phase power line 12V is determined when motor drive device 1 is in state E1 or state E2.

[0175] A short circuit between V-phase power line 12V and W-phase power line 12W is determined when motor drive device 1 is in state A1 or state F2.

[0176] A short circuit between W-phase power line 12W and U-phase power line 12U is determined when motor drive device 1 is in state F1, state A2, or state F3.

[0177] A short circuit is determined to have occurred among U-phase power line 12U, V-phase power line 12V, and W-phase power line 12W when motor drive device 1 is in state E1, state E2, or state H3.

[0178] A ground fault is determined to have occurred in U-phase power line 12U when motor drive device 1 is in state F1, F2, A3, or state D4.

[0179] A ground fault is determined to have occurred in the V-phase power line 12V when the motor drive device 1 is in state F1, F2, A3, or E4.

[0180] A ground fault is determined to have occurred in W-phase power line 12W when motor drive device 1 is in state F1, F2, A3, or A4.

[0181] The switching elements S1, S2, S3, S4, S5 and S6, switches 32U, 32V and 32W, U-phase power line 12U, V-phase power line 12V and W-phase power line 12W are all determined to be normal (i.e., no faults at all) when the motor drive device 1 is in states A1, A2, A3, A4, A5, A6 and A7.

[0182] As shown in Figure 14, when switching command unit 17 outputs an ON / OFF command in accordance with command patterns Q1 to Q7 and dynamic braking command unit 18 outputs an open / close command, motor drive device 1 can be in a variety of states depending on the type and location of the fault. If the type and location of the fault differs, the state that motor drive device 1 can be in will also differ. By comparing the state of motor drive device 1 determined based on the state reference tables of Figures 7 to 13 with the fault determination conditions shown in Figure 14, it is possible to detect whether a fault exists, and if a fault exists, the type and location of the fault can be identified.

[0183] By outputting ON / OFF commands from the switching command unit 17 and outputting open / close commands from the dynamic braking command unit 18 for all of the command patterns Q1 to Q7 in sequence, the state of the motor drive device 1 under each of the command patterns Q1 to Q7 can be determined. However, when command patterns Q1, Q2, and Q3 are executed in sequence, the nature and location of the fault may be identified at an early stage before the execution of all command patterns is completed. For example, if the state of the motor drive device 1 determined under command pattern Q1 is A1 and the state of the motor drive device 1 determined under the next command pattern Q2 is B2, an open fault in the upper arm switching element S3 of the V-phase can be detected without executing subsequent command patterns Q3 to Q7. Therefore, it is preferable to execute the state determination process and fault detection process by the determination unit 24 each time each of the command patterns Q1 to Q7 is executed, and to stop execution of subsequent command patterns once the nature and location of the fault have been identified through the fault detection process by the determination unit 24. This reduces the computational load associated with the fault detection process.

[0184] <Operation Flow of Failure Determination Processing in Motor Drive Device According to One Embodiment of the Present Disclosure> FIG. 15 is a flowchart showing the operation flow of failure determination processing in a motor drive device according to one embodiment of the present disclosure.

[0185] 15, the numerical portion of the symbols Q1 to Q7 that identify the seven types of command patterns is represented by N. That is, the seven types of command patterns are represented by QN (where N is a natural number from 1 to 7).

[0186] In step S101, a host control unit (not shown) of the switching command unit 17 and the dynamic braking command unit 18 sets N to 1 as an initial value.

[0187] In step S102, the upper control unit outputs the command pattern QN to the switching command unit 17 and the dynamic braking command unit 18. In response to this, the switching command unit 17 outputs an ON / OFF command in accordance with the command pattern QN, and the dynamic braking command unit 18 outputs an open / close command in accordance with the command pattern QN.

[0188] In step S103, the voltage detector 15 detects the value of the DC voltage in the DC link. Data on the value of the DC voltage detected in step S102 is sent to the calculator 22.

[0189] In step S104, the calculation unit 22 calculates a current reference value corresponding to the command pattern QN in accordance with the calculation formula stored in the storage unit 21, using the value of the DC voltage in the DC link detected by the voltage detection unit 15. Information about the current reference value calculated by the calculation unit 22 is sent to the comparison unit 23.

[0190] In step S105, the current detection unit 13 detects the values ​​of the U-phase current and the V-phase current output from the inverter 11. Information about the current values ​​detected by the current detection unit 13 is sent to the comparison unit 23.

[0191] In step S106, the overcurrent detection unit 14 detects whether or not an overcurrent is flowing in the lower arm of each phase in the inverter 11. Information regarding the presence or absence of an overcurrent detected by the overcurrent detection unit 14 is sent to the comparison unit 23.

[0192] In step S107, a state determination process is executed. In the state determination process, comparison unit 23 compares the current reference value under command pattern QN with the detection result by current detection unit 13. Determination unit 24 determines the current state of motor drive device 1, for which command pattern QN is being commanded, based on the comparison result by comparison unit 23 under command pattern QN and whether or not overcurrent has been detected by overcurrent detection unit 14.

[0193] In step S108, the determination unit 24 compares the determination result in the state determination process with the fault determination conditions to check whether it is possible to determine the type and location of the fault or whether the system is normal. If it is possible to determine the type and location of the fault or whether the system is normal, the process proceeds to step S112, and if it is not possible to determine the type and location of the fault or whether the system is normal, the process proceeds to step S109.

[0194] In step S109, the upper control unit determines whether N is 7. If N is not 7, N is incremented by 1 in step S110, and then the process returns to step S102. If N is 7, the process proceeds to step S112.

[0195] In step S112, the determination unit 24 determines whether or not there is a malfunction, and if there is a malfunction, identifies the type and location of the malfunction based on the result of checking the determination result in the state determination process against the malfunction determination conditions.

[0196] <Relationship Between Faults Under Fault Determination Conditions and the State of the Motor Drive Device in Each Command Pattern> The relationship between faults under the fault determination conditions and the state of the motor drive device 1 in each command pattern Q1 to Q7 will be described with reference to Figures 16A to 47G. As described above, in command patterns Q1 to Q7, specific switching elements are commanded to be on for a predetermined time, and in Figures 16A to 47G, the reference symbols of the switching elements to be commanded to be on are marked with a white circle. Also, in Figures 16A to 47G, the AC power supply 2, converter 10, current detection unit 13, overcurrent detection unit 14, voltage detection unit 15, switching command unit 17, dynamic braking command unit 18, and fault detection unit 19 are not shown.

[0197] 16A to 16C are circuit diagrams showing the state of the motor drive device when an open circuit failure occurs in the switching element of the U-phase upper arm. Fig. 16A shows the state of the motor drive device operating under command pattern Q1, Fig. 16B shows the state of the motor drive device operating under command pattern Q2, and Fig. 16C shows the state of the motor drive device operating under command pattern Q3.

[0198] 16A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The U-phase upper arm switching element S1 has an open fault and does not turn ON even when it receives an ON command, so the current from the DC link does not flow out to the AC side through the inverter 11. Therefore, the U-phase current I U is "0", and the V-phase current I V is "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B1.

[0199] 16B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the U-phase upper arm switching element S1 has an open fault, it does not turn ON even when it receives an ON command, but the V-phase upper arm switching element S3 and the W-phase lower arm switching element S6 receive an ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of μsec) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. V U-phase current I UThe W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0200] When command pattern Q1 and command pattern Q2 are executed, states B1 and A2 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15. Based on the fault determination conditions shown in FIG. 14, the nature and location of the fault can be identified as an open fault in the U-phase upper arm switching element S1. Execution of subsequent command patterns Q3 to Q7 is not necessary to identify an open fault in switching element S1. For example, as shown in FIG. 16C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 outputs a close command to close switches 32U, 32V, and 32W. Whether switching element S1 in the U-phase upper arm is normal or has an open fault, there is no change in the current path based on the ON switching elements S2, S4, and S5 in the inverter 11. Therefore, it is not necessary to execute the state determination process and the failure determination process under the command pattern Q3.

[0201] 17A to 17C are circuit diagrams showing the state of the motor drive device when an open circuit failure occurs in the switching element of the upper arm of phase V. Fig. 17A shows the state of the motor drive device operating under command pattern Q1, Fig. 17B shows the state of the motor drive device operating under command pattern Q2, and Fig. 17C shows the state of the motor drive device operating under command pattern Q3.

[0202] 17A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The V-phase upper arm switching element S3 has an open fault and does not turn ON even when it receives an ON command, but the U-phase upper arm switching element S1 and the W-phase lower arm switching element S6 receive an ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U The U-phase current I flows to the AC side as a U is the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V and the V-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. V V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-VDC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0203] 17B, ​​in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The V-phase upper arm switching element S3 has an open fault and does not turn ON even when it receives an ON command, so the current from the DC link does not flow out to the AC side through the inverter 11. Therefore, the U-phase current I U is "0", and the V-phase current I V is "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B2.

[0204] When command pattern Q1 and command pattern Q2 are executed, states A1 and B2 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15. Based on the fault determination conditions shown in FIG. 14, the nature and location of the fault can be identified as an open fault in the upper V-phase switching element S1. Execution of subsequent command patterns Q3 to Q7 is not necessary to identify an open fault in switching element S1. For example, as shown in FIG. 17C, in command pattern Q3, the switching command unit 17 outputs an ON command to the lower U-phase switching element S2, the lower V-phase switching element S4, and the upper W-phase switching element S5. Furthermore, the dynamic brake command unit 18 outputs a close command to close switches 32U, 32V, and 32W. Whether the upper V-phase switching element S3 is normal or has an open fault, there is no change in the current path based on the ON switching elements S2, S4, and S5 in the inverter 11. Therefore, it is not necessary to execute the state determination process and the failure determination process under the command pattern Q3.

[0205] 18A to 18C are circuit diagrams showing the state of the motor drive device when an open circuit failure occurs in the switching element of the W-phase upper arm. Fig. 18A shows the state of the motor drive device operating under command pattern Q1, Fig. 18B shows the state of the motor drive device operating under command pattern Q2, and Fig. 18C shows the state of the motor drive device operating under command pattern Q3.

[0206] 18A , in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the W-phase upper arm switching element S5 has an open fault, it does not turn ON even when it receives an ON command, but the U-phase upper arm switching element S1 and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of μsec) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U The U-phase current I flows to the AC side as a U is the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V and the V-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. V V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current IV is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0207] 18B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the W-phase upper arm switching element S5 is normal or has an open circuit fault, there is no change in the current path based on the switching elements S2, S3, and S6 that are in the ON state within the inverter 11. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W U-phase current I U The W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0208] 18C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The W-phase upper arm switching element S5 has an open fault and does not turn ON even when it receives an ON command, so the current from the DC link does not flow out to the AC side through the inverter 11. Therefore, the U-phase current I U is "0", and the V-phase current I V is "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B3.

[0209] Once command patterns Q1 to Q3 have been executed, states A1, A2, and B3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, and it is possible to identify that the type and location of the fault is an open fault in switching element S5 of the W-phase upper arm based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify an open fault in switching element S5.

[0210] 19A to 19C are circuit diagrams showing the state of the motor drive device when an open circuit failure occurs in the switching element of the U-phase lower arm. Fig. 19A shows the state of the motor drive device operating under command pattern Q1, Fig. 19B shows the state of the motor drive device operating under command pattern Q2, and Fig. 19C shows the state of the motor drive device operating under command pattern Q3.

[0211] 19A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the U-phase lower arm switching element S2 is normal or has an open circuit fault, there is no change in the current path based on the switching elements S1, S4, and S6 that are in the ON state within the inverter 11. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U The U-phase current I flows to the AC side as a U is the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V and the V-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. V V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0212] 19B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the U-phase lower arm switching element S2 has an open fault, it does not turn ON even when it receives an ON command, but the V-phase upper arm switching element S3 and the W-phase lower arm switching element S6 receive an ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of μsec) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V 19B, the U-phase current I flows to the AC side, and then flows out to the DC link through the dynamic brake resistor 31V, the switch 32V, the switch 32W, the dynamic brake resistor 31W, and the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U becomes "0", and the V-phase current I V is "V DC / (2R DB Therefore, the state of the motor drive device 1 is C2.

[0213] When command pattern Q1 and command pattern Q2 are executed, states A1 and C2 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in FIG. 14, the type and location of the fault can be identified as an open fault in switching element S2 of the U-phase lower arm. Execution of subsequent command patterns Q3 to Q7 is not necessary to identify an open fault in switching element S2. For example, as shown in FIG. 19C, in command pattern Q3, switching command unit 17 outputs ON commands to switching element S2 of the U-phase lower arm, switching element S4 of the V-phase lower arm, and switching element S5 of the W-phase upper arm. Since switching element S2 of the U-phase lower arm has an open fault, it does not turn ON even when commanded to do so, but switching element S4 of the V-phase lower arm and switching element S5 of the W-phase upper arm turn ON in response to the ON commands. The time during which the ON command is output is a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through the switching element S5 as the W-phase current I W 19C, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic braking resistor 31W, the switch 32W, the switch 32V, the dynamic braking resistor 31V, and the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U becomes "0", and the V-phase current I V is "-V DC / (2R DB Therefore, the state of the motor driving device 1 is C3.

[0214] 20A and 20B are circuit diagrams showing the state of the motor drive device when an open circuit failure occurs in a switching element of the V-phase lower arm. Fig. 20A shows the state of the motor drive device operating under command pattern Q1, and Fig. 20B shows the state of the motor drive device operating under command pattern Q2.

[0215] As shown in FIG. 20A , in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the V-phase lower arm switching element S4 has an open fault, it does not turn ON even when it receives an ON command, but the U-phase upper arm switching element S1 and the W-phase lower arm switching element S6 receive an ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of μsec) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U 20A, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic braking resistor 31U, the switch 32U, the switch 32W, the dynamic braking resistor 31W, and the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / (2R DB ) and the V-phase current I V becomes "0." Therefore, the state of the motor drive device 1 is C1.

[0216] As shown in Figure 20B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the V-phase lower arm switching element S4 is normal or has an open circuit fault, there is no change in the current path based on the switching elements S2, S3, and S6 that are in the ON state within the inverter 11. The time during which the ON command is output is "short" (for example, several tens of microseconds) so that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. V U-phase current I U The W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0217] If, at the stage where command pattern Q1 and command pattern Q2 have been executed, states C1 and A2 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, it is possible to identify that the type and location of the fault is an open fault in switching element S4 of the V-phase lower arm, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q3 to Q7 is not necessary to identify an open fault in switching element S4.

[0218] 21A to 21C are circuit diagrams showing the state of the motor drive device when an open circuit failure occurs in the switching element of the W-phase lower arm. Fig. 21A shows the state of the motor drive device operating under command pattern Q1, Fig. 21B shows the state of the motor drive device operating under command pattern Q2, and Fig. 21C shows the state of the motor drive device operating under command pattern Q3.

[0219] As shown in Figure 21A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The W-phase lower arm switching element S6 has an open fault and does not turn ON even when it receives an ON command, but the U-phase upper arm switching element S1 and the V-phase lower arm switching element S4 receive the ON command and turn ON. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the U-phase current I through switching element S1 U 21A, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic brake resistor 31U, the switch 32U, the switch 32V, the dynamic brake resistor 31V, and the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "V DC / (2RDB ) and the V-phase current I V is "-V DC / (2R DB )) Therefore, the state of the motor drive device 1 is D1.

[0220] 21B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the W-phase lower arm switching element S6 has an open circuit fault, it does not turn ON even when it receives an ON command, but the U-phase lower arm switching element S2 and the V-phase upper arm switching element S3 receive an ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the V-phase current I V 21B, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic brake resistor 31V, the switch 32V, the switch 32W, the dynamic brake resistor 31W, and the switching element S2 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / (2R DB ) and the V-phase current I V is "V DC / (2R DB Therefore, the state of the motor drive device 1 is D2.

[0221] 21C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the W-phase lower arm switching element S6 is normal or has an open circuit fault, there is no change in the current path based on the switching elements S2, S4, and S5 that are in the ON state within the inverter 11. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V U-phase current I U The V-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. V The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A3.

[0222] Once command patterns Q1 to Q3 have been executed, and states D1, D2, and A3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, it is possible to identify that the type and location of the fault is an open fault in switching element S6 of the W-phase lower arm, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify an open fault in switching element S6.

[0223] 22A to 22C are circuit diagrams showing the state of the motor drive device when a short circuit occurs in the switching element of the U-phase upper arm. Fig. 22A shows the state of the motor drive device operating under command pattern Q1, Fig. 22B shows the state of the motor drive device operating under command pattern Q2, and Fig. 22C shows the state of the motor drive device operating under command pattern Q3.

[0224] As shown in Figure 22A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S1 that is commanded to be ON is normal or short-circuited, there is no change in the current path based on the switching elements S1, S4, and S6. The time during which the ON command is output is "short" (for example, several tens of microseconds) so that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U The U-phase current I flows to the AC side as a U is the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4.W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0225] 22B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The U-phase upper arm switching element S1 is short-circuited, and the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and operate ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S1 and S2, causing an overcurrent to flow in the U-phase upper arm and lower arm. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the U phase of the inverter 11. Therefore, the state of the motor drive device 1 is G2.

[0226] 22C , in command pattern Q3, the switching command unit 17 outputs an ON command to the switching element S2 of the U-phase lower arm, the switching element S4 of the V-phase lower arm, and the switching element S5 of the W-phase upper arm. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The U-phase upper arm switching element S1 is short-circuited, and the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and turn ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S1 and S2, causing an overcurrent to flow in the U-phase upper and lower arms. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the U phase of the inverter 11. Therefore, the state of the motor drive device 1 is G3.

[0227] Once command patterns Q1 to Q3 have been executed, states A1, G2, and G3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, and it is then possible to identify that the type and location of the fault is a short circuit in switching element S1 of the U-phase upper arm, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit in switching element S1.

[0228] 23A to 23C are circuit diagrams showing the state of the motor drive device when a short circuit occurs in the switching element of the upper arm of phase V. Fig. 23A shows the state of the motor drive device operating under command pattern Q1, Fig. 23B shows the state of the motor drive device operating under command pattern Q2, and Fig. 23C shows the state of the motor drive device operating under command pattern Q3.

[0229] 23A , in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The V-phase upper arm switching element S3 is short-circuited, and the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive ON commands and turn ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S3 and S4, causing an overcurrent to flow in the V-phase upper arm and lower arm. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the V phase of the inverter 11. Therefore, the state of the motor drive device 1 is G1.

[0230] As shown in Figure 23B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S3 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S2, S3, and S6. The time for which the ON command is output is a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W U-phase current I UThe W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0231] 23C , in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The V-phase upper arm switching element S3 is short-circuited, and the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive an ON command and operate ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S3 and S4, causing an overcurrent to flow in the V-phase upper arm and lower arm. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the V phase of the inverter 11. Therefore, the state of the motor drive device 1 is G3.

[0232] Once command patterns Q1 to Q3 have been executed, states G1, A2, and G3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, and it is then possible to identify the type and location of the fault as a short circuit in switching element S3 of the upper arm of V-phase, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit in switching element S3.

[0233] 24A to 24C are circuit diagrams showing the state of the motor drive device when a short circuit occurs in the switching element of the W-phase upper arm. Fig. 24A shows the state of the motor drive device operating under command pattern Q1, Fig. 24B shows the state of the motor drive device operating under command pattern Q2, and Fig. 24C shows the state of the motor drive device operating under command pattern Q3.

[0234] 24A , in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The W-phase upper arm switching element S5 is short-circuited, and the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive an ON command and operate ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S5 and S6, causing an overcurrent to flow in the W-phase upper and lower arms. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the W phase of the inverter 11. Therefore, the state of the motor drive device 1 is G1.

[0235] 24B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The W-phase upper arm switching element S5 is short-circuited, and the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive ON commands and operate ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S5 and S6, causing an overcurrent to flow in the W-phase upper arm and lower arm. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the W phase of the inverter 11. Therefore, the state of the motor drive device 1 is G2.

[0236] As shown in Fig. 24C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S5 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S2, S4, and S5. The time for which the ON command is output is "short" (for example, several tens of microseconds) so that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V U-phase current I UThe V-phase current I flows out to the DC link through the switching element S1 of the lower arm of the U-phase. V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A3.

[0237] At the stage where command patterns Q1 to Q3 have been executed, if states G1, G2, and A3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, it is possible to identify that the type and location of the fault is a short circuit in switching element S5 of the W-phase upper arm based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit in switching element S5.

[0238] 25A to 25C are circuit diagrams showing the state of the motor drive device when a short circuit occurs in the switching element of the U-phase lower arm. Fig. 25A shows the state of the motor drive device operating under command pattern Q1, Fig. 25B shows the state of the motor drive device operating under command pattern Q2, and Fig. 25C shows the state of the motor drive device operating under command pattern Q3.

[0239] 25A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. The U-phase lower arm switching element S2 is short-circuited, and the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive an ON command and operate ON. Therefore, the positive side power line and the negative side power line in the DC link are short-circuited via the switching elements S1 and S2, and an overcurrent flows in the U-phase upper arm and lower arm. The U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the U phase of the inverter 11. Therefore, the state of the motor drive device 1 is G1.

[0240] As shown in Figure 25B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S2 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S2, S3, and S6. The time for which the ON command is output is a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W U-phase current I U The W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. WThe U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0241] 25C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S2 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S2, S4, and S5. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V U-phase current I U The V-phase current I flows out to the DC link through the switching element S1 of the lower arm of the U-phase. V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3RDB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A3.

[0242] Once command patterns Q1 to Q3 have been executed, and states G1, A2, and A3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, it is possible to identify that the type and location of the fault is a short circuit in switching element S2 of the W-phase upper arm, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit in switching element S2.

[0243] 26A to 26C are circuit diagrams showing the state of the motor drive device when a short circuit occurs in the switching element of the V-phase lower arm. Fig. 26A shows the state of the motor drive device operating under command pattern Q1, Fig. 26B shows the state of the motor drive device operating under command pattern Q2, and Fig. 26C shows the state of the motor drive device operating under command pattern Q3.

[0244] As shown in Fig. 26A, in command pattern Q1, the switching command unit 17 outputs an ON command to the switching element S1 of the upper arm of the U-phase, the switching element S4 of the lower arm of the V-phase, and the switching element S6 of the lower arm of the W-phase. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S4 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S1, S4, and S6. The time for which the ON command is output is "short" (for example, several tens of microseconds) so that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U The U-phase current I flows to the AC side as a U is the U-phase current I flowing through the switch 32V and the dynamic brake resistor 31V.V and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0245] 26B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The V-phase upper arm switching element S3 is short-circuited, and the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive ON commands and turn ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S3 and S4, causing an overcurrent to flow in the V-phase upper arm and lower arm. U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the V phase of the inverter 11. Therefore, the state of the motor drive device 1 is G2.

[0246] 26C , in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the V-phase lower arm switching element S4 is normal or short-circuited, there is no change in the current path based on the switching elements S2, S4, and S5 that are turned ON in the inverter 11. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V U-phase current I U The V-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. V The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A3.

[0247] Once command patterns Q1 to Q3 have been executed, states A1, G2, and A3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, and it is then possible to identify that the type and location of the fault is a short circuit in switching element S4 of the U-phase upper arm, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit in switching element S4.

[0248] 27A to 27C are circuit diagrams showing the state of the motor drive device when a short circuit occurs in the switching element of the W-phase lower arm. Fig. 27A shows the state of the motor drive device operating under command pattern Q1, Fig. 27B shows the state of the motor drive device operating under command pattern Q2, and Fig. 27C shows the state of the motor drive device operating under command pattern Q3.

[0249] As shown in Figure 27A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S6 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S1, S4, and S6. The time for which the ON command is output is a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U The U-phase current I flows to the AC side as a U is the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4. WThe U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0250] As shown in Figure 27B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Whether the switching element S6 for which the ON command is issued is normal or short-circuited, there is no change in the current path based on the switching elements S2, S3, and S6. The time for which the ON command is output is a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 to the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W U-phase current I U The W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3RDB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0251] 27C , in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. The dynamic brake command unit 18 also outputs a close command to close the switches 32U, 32V, and 32W. The W-phase lower arm switching element S6 is short-circuited, and the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive an ON command and operate ON. Therefore, the positive and negative power lines in the DC link are short-circuited via the switching elements S5 and S6, causing an overcurrent to flow in the W-phase upper and lower arms. The U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, an overcurrent occurs in the W phase of the inverter 11. Therefore, the state of the motor drive device 1 is G3.

[0252] Once command patterns Q1 to Q3 have been executed, states A1, A2, and G3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, and it is then possible to identify the type and location of the fault as a short circuit in switching element S6 of the upper arm of V-phase based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit in switching element S6.

[0253]

[0111] Figures 28A and 28B are circuit diagrams showing the state of the motor drive device when an open-circuit fault occurs in the switches of two or more phases of the dynamic braking circuit. Figure 28A shows the state of the motor drive device operating under command pattern Q1, and Figure 28B shows the state of the motor drive device operating under command pattern Q2. Figures 28A and 28B show, as an example, a case where an open-circuit fault occurs in the switches 32U and 32V of the dynamic braking circuit 16.

[0254] As shown in FIG. 28A , in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command, but the switches 32U and 32V, which have an open fault, remain open, and only the switch 32W is closed. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switches 32U and 32V have an open fault, no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B1.

[0255] As shown in FIG. 28B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command, but the switches 32U and 32V, which have an open fault, remain open, and only the switch 32W is closed. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switches 32U and 32V have an open fault, no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B2.

[0256] 28A and 28B show, as an example, a case where the switches 32U and 32V of the dynamic braking circuit 16 have an open-circuit fault. Even in the case of an open-circuit fault in the switches 32U and 32V, an open-circuit fault in the switches 32V and 32W, an open-circuit fault in the switches 32W and 32U, or an open-circuit fault in the switches 32U, 32V, and 32W of the dynamic braking circuit 16, no motor current flows through the motor 3, and at least two of the switches 32U, 32V, and 32W have an open-circuit fault, so no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B2.

[0257] If, at the stage where command patterns Q1 and Q2 have been executed, the states B1 and B2 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as an open-circuit fault in the switches of two or more phases of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q3 to Q7 is not necessary to identify an open-circuit fault in the switches of two or more phases of the dynamic braking circuit 16.

[0258] Figures 29A and 29B are circuit diagrams showing the state of the motor drive device when an open fault occurs in the U-phase switch of the dynamic braking circuit. Figure 29A shows the state of the motor drive device operating under command pattern Q1, and Figure 29B shows the state of the motor drive device operating under command pattern Q2.

[0259] 29A , in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command, so the switches 32V and 32W are closed, but the U-phase switch 32U, which has an open fault, remains open. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of μsec) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switch 32U has an open fault, only the U-phase current I flows from the DC link to the AC side via the inverter 11. U Therefore, no current flows through the switch 32U, which has an open fault. Therefore, no current flows through the switch 32V and the dynamic braking resistor 31V, and the switch 32W and the dynamic braking resistor 31W. Therefore, the U-phase current I U becomes "0", and the V-phase current I Vbecomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B1.

[0260] As shown in Figure 29B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, because the dynamic brake command unit 18 outputs a close command, the switches 32V and 32W are closed, but the U-phase switch 32U, which has an open fault, remains open. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. No motor current flows through the motor 3. Therefore, the current from the DC link is converted into the V-phase current I through switching element S3. V 29B, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic brake resistor 31V, the switch 32V, the switch 32W, the dynamic brake resistor 31W, and the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U becomes "0", and the V-phase current I V is "V DC / (2R DB Therefore, the state of the motor drive device 1 is C2.

[0261] If, at the stage where command patterns Q1 and Q2 have been executed, states B1 and C2 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as an open-circuit fault in the U-phase switch 32U of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q3 to Q7 is not necessary to identify an open-circuit fault in the U-phase switch 32U of the dynamic braking circuit 16.

[0262] Figures 30A and 30B are circuit diagrams showing the state of the motor drive device when an open fault occurs in the V-phase switch of the dynamic braking circuit. Figure 30A shows the state of the motor drive device operating under command pattern Q1, and Figure 30B shows the state of the motor drive device operating under command pattern Q2.

[0263] As shown in Figure 30A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command, so the switches 32U and 32W are closed, but the V-phase switch 32V, which has an open fault, remains open. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 as the U-phase current I U 30A, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic braking resistor 31U, the switch 32U, the switch 32W, the dynamic braking resistor 31W, and the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / (2RDB ) and the V-phase current I V becomes "0." Therefore, the state of the motor drive device 1 is C1.

[0264] As shown in FIG. 30B , in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs a close command, so the switches 32U and 32W are closed, but the V-phase switch 32V, which has an open fault, remains open. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switch 32V has an open fault, no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B2.

[0265] If, at the stage where command patterns Q1 and Q2 have been executed, states C1 and B2 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as an open-circuit fault in the V-phase switch 32V of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q3 to Q7 is not necessary to identify an open-circuit fault in the V-phase switch 32V of the dynamic braking circuit 16.

[0266] Figures 31A to 31C are circuit diagrams showing the state of the motor drive device when an open fault occurs in the W-phase switch of the dynamic braking circuit. Figure 31A shows the state of the motor drive device operating under command pattern Q1, Figure 31B shows the state of the motor drive device operating under command pattern Q2, and Figure 31C shows the state of the motor drive device operating under command pattern Q3.

[0267] As shown in Figure 31A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command, so the switches 32U and 32V are closed, but the W-phase switch 32W, which has an open fault, remains open. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 as the U-phase current I U 31A, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic brake resistor 31U, the switch 32U, the switch 32V, the dynamic brake resistor 31V, and the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "V DC / (2R DB ) and the V-phase current I V is "-V DC / (2R DB )) Therefore, the state of the motor drive device 1 is D1.

[0268] As shown in Figure 31B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, because the dynamic brake command unit 18 outputs a close command, the switches 32U and 32V are closed, but the W-phase switch 32W, which has an open fault, remains open. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 as the V-phase current I V 31B, the U-phase current I flows to the AC side, and then flows out to the DC link through the dynamic brake resistor 31V, the switch 32V, the switch 32U, the dynamic brake resistor 31U, and the switching element S2 of the lower arm of the U-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / (2R DB ) and the V-phase current I V is "V DC / (2R DB Therefore, the state of the motor drive device 1 is D2.

[0269] As shown in FIG. 31C , in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 outputs a close command, so the switches 32U and 32V are closed, but the W-phase switch 32W, which has an open fault, remains open. The U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switch 32W has an open fault, no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is B3.

[0270] Once the states D1, D2, and B3 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15 at the stage where command patterns Q1 to Q3 have been executed, it is possible to identify the type and location of the fault as an open-circuit fault in the W-phase switch 32W of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify an open-circuit fault in the W-phase switch 32W of the dynamic braking circuit 16.

[0271]

[0083] Figures 32A and 32B are circuit diagrams showing the state of the motor drive device when a short circuit occurs between the U and V phases of the dynamic braking circuit. Figure 30A shows the state of the motor drive device operating under command pattern Q4, and Figure 30B shows the state of the motor drive device operating under command pattern Q5.

[0272] As shown in Figure 32A, in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, but the switches 32U and 32V are short-circuited, and only the switch 32W is opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the U-phase current I through the U-phase upper arm switching element S1 U and the V-phase current I through the V-phase upper arm switching element S3 V does not flow to the motor 3, and the switch 32W is open, so the W-phase current I W Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is A4.

[0273] As shown in Figure 32B, in command pattern Q5, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs an open command, but the switches 32U and 32V are short-circuited, and only the switch 32W is opened. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and turn ON. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. No motor current flows through the motor 3. Therefore, the current from the DC link flows through switching element S1 to the U-phase current IU 32B, the U-phase current I flows to the AC side, and then flows out to the DC link through the dynamic brake resistor 31U, the switch 32U, the switch 32V, the dynamic brake resistor 31V, and the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "V DC / (2R DB ) and the V-phase current I V is "-V DC / (2R DB Therefore, the state of the motor drive device 1 is B5.

[0274] Once the command patterns Q1 to Q5 have been executed, and the states A4 and B5 of the motor drive device 1 are acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as a short circuit in the U-phase switch 32U and the V-phase switch 32V of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q6 and Q7 is not necessary to identify a short circuit in the U-phase switch 32U and the V-phase switch 32V of the dynamic braking circuit 16.

[0275] FIG. 33 is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the V-phase and W-phase switches of the dynamic braking circuit, and shows the state of the motor drive device operating under command pattern Q4.

[0276] 33, in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, but the switches 32V and 32W are short-circuited, and only the switch 32U is opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and operate ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Because no motor current flows through the motor 3 and the switches 32V and 32W are short-circuited, the current from the DC link flows through the switching element S3 to the V-phase current I V 33, the U-phase current I flows to the AC side, and then flows out to the DC link through the dynamic brake resistor 31V, the switch 32V, the switch 32W, the dynamic brake resistor 31W, and the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U becomes "0", and the V-phase current I V is "V DC / (2R DB Therefore, the state of the motor drive device 1 is B4.

[0277] If, at the stage where command patterns Q1 to Q4 have been executed, state B4 of the motor drive device 1 is acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as a short circuit in the V-phase switch 32V and the W-phase switch 32W of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q5 to Q7 is not necessary to identify a short circuit in the V-phase switch 32V and the W-phase switch 32W of the dynamic braking circuit 16.

[0278] FIG. 34 is a circuit diagram showing the state of the motor drive device when a short circuit occurs in the W-phase and U-phase switches of the dynamic braking circuit, and shows the state of the motor drive device operating under command pattern Q4.

[0279] 34, in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, but the switches 32W and 32U are short-circuited, and only the switch 32V is opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Because no motor current flows through the motor 3 and the switches 32W and 32U are short-circuited, the current from the DC link flows through the switching element S1 to the U-phase current I U 34, the U-phase current I flows to the AC side as a current, and then flows out to the DC link through the dynamic braking resistor 31U, the switch 32U, the switch 32W, the dynamic braking resistor 31W, and the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / (2R DB ) and the V-phase current I V becomes "0." Therefore, the state of the motor drive device 1 is C4.

[0280] If, at the stage where command patterns Q1 to Q4 have been executed, state C4 of the motor drive device 1 is acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as a short circuit in the W-phase switch 32W and the U-phase switch 32U of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q5 to Q7 is not necessary to identify a short circuit in the W-phase switch 32W and the U-phase switch 32U of the dynamic braking circuit 16.

[0281] FIG. 35 is a circuit diagram showing the state of the motor drive device when all three phase switches of the dynamic braking circuit are short-circuited, and shows the state of the motor drive device operating under command pattern Q4.

[0282] 35 , in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs an open command, but the switches 32U, 32V, and 32W are short-circuited. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and operate ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switches 32U, 32V, and 32W are short-circuited, the current from the DC link flows through the dynamic brake resistor 31U and the switch 32U, as the U-phase current I U and the V-phase current I flows through the dynamic braking resistor 31V and the switch 32V via the switching element S3. V Regarding the W phase, the W phase current I flows into the DC link via the switching element S6. W is the U-phase current I flowing through the dynamic braking resistor 31U and the switch 32U. Uand the V-phase current I flowing through the dynamic braking resistor 31V and the switch 32V. V In FIG. 35, the U-phase current I U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is F4.

[0283] If, at the stage where command patterns Q1 to Q4 have been executed, state F4 of the motor drive device 1 is acquired based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15, it is possible to identify the type and location of the fault as a short circuit in the switches of all three phases of the dynamic braking circuit 16, based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q5 to Q7 is not necessary to identify a short circuit in the switches of all three phases of the dynamic braking circuit 16.

[0284] FIG. 36 is a circuit diagram showing the state of the motor drive device when a break occurs in the U-phase power line, and shows the state of the motor drive device operating under command pattern Q6.

[0285] As shown in Fig. 36, in command pattern Q6, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, and the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "long time" (for example, several tens of milliseconds) such that a motor current flows through the motor 3 during the ON command. Since the U-phase power line 12U is disconnected, the U-phase current I UTherefore, the current from the DC link flows through the switching element S3 as the V-phase current I V and flows to the AC side as a W-phase current I W 36, the U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U becomes "0", and the V-phase current I V is "greater than 0." Therefore, the state of the motor driving device 1 is B6.

[0286] If, at the stage where command patterns Q1 to Q6 have been executed, state B6 of motor drive device 1 is acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, it is possible to identify the type and location of the fault as a break in U-phase power line 12U based on the fault determination conditions shown in Figure 14. Execution of command pattern Q7 thereafter is not necessary to identify a break in U-phase power line 12U.

[0287] FIG. 37 is a circuit diagram showing the state of the motor drive device when a break occurs in the V-phase power line, and shows the state of the motor drive device operating under command pattern Q6.

[0288] As shown in Fig. 37, in command pattern Q6, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, and the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "long time" (for example, several tens of milliseconds) such that a motor current flows through the motor 3 during the ON command. Since the V-phase power line 12V is disconnected, the V-phase current I V Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I Uand flows to the AC side as a W-phase current I W As a result, the U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U is "greater than 0", and the V-phase current I V becomes "0." Therefore, the state of the motor driving device 1 is C6.

[0289] If, at the stage where command patterns Q1 to Q6 have been executed, state C6 of motor drive device 1 is acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, it is possible to identify the type and location of the fault as a break in V-phase power line 12V based on the fault determination conditions shown in Fig. 14. Execution of command pattern Q7 thereafter is not necessary to identify a break in V-phase power line 12V.

[0290] 38A and 38B are circuit diagrams showing the state of the motor drive device when a break occurs in the W-phase power line, with Fig. 38A showing the state of the motor drive device operating under command pattern Q6 and Fig. 38B showing the state of the motor drive device operating under command pattern Q7.

[0291] As shown in FIG. 38A , in command pattern Q6, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs an open command, and the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "long time" (e.g., several tens of milliseconds) long enough for motor current to flow through the motor 3 during the ON command. Because the W-phase power line 12W is disconnected, a current path returning from the motor 3 to the W-phase lower arm switching element S6 of the inverter 11 cannot be secured. Therefore, the U-phase current I U and V-phase current I V Therefore, the U-phase current I U becomes "0", and the V-phase current IV becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is D6.

[0292] As shown in Figure 38B, in command pattern Q7, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and turn ON. The ON command is output for a "long time" (for example, several tens of milliseconds) that is long enough for a motor current to flow through the motor 3 during the ON command. Since the W-phase power line 12W is disconnected, the W-phase current I W Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I U and flows into the AC side as a V-phase current I V As a result, the U-phase current I flows out to the DC link through the switching element S4 of the lower arm of the V-phase. U is "greater than 0", and the V-phase current I V is "less than 0." Therefore, the state of the motor driving device 1 is A7.

[0293] When command patterns Q1 to Q7 are executed, states D6 and A7 of the motor drive device 1 are obtained based on the detection results of the current detection unit 13, the overcurrent detection unit 14, and the voltage detection unit 15. Based on the fault determination conditions shown in Figure 14, it is possible to identify that the content and location of the fault is a break in the W-phase power line 12W.

[0294] 39A and 39B are circuit diagrams showing the state of the motor drive device when a break occurs in two or more phase power lines. Fig. 39A shows the state of the motor drive device operating under command pattern Q6, and Fig. 39B shows the state of the motor drive device operating under command pattern Q7. Figs. 39A and 39B show, as an example, a case where U-phase power line 12U and V-phase power line 12V are broken.

[0295] As shown in FIG. 39A , in command pattern Q6, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs an open command, and the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "long time" (e.g., several tens of milliseconds) long enough for motor current to flow through the motor 3 during the ON command. Because the U-phase power line 12U and the V-phase power line 12V are disconnected, a current path from the U-phase upper arm switching element S1 and the V-phase upper arm switching element S3 of the inverter 11 to the motor 3 cannot be secured. Therefore, the U-phase current I U and V-phase current I V Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is D6.

[0296] As shown in FIG. 38B , in command pattern Q7, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and turn ON. The ON command is output for a "long time" (e.g., several tens of milliseconds) long enough for motor current to flow through the motor 3 during the ON command. Because the U-phase power line 12U and the V-phase power line 12V are disconnected, the current path from the U-phase upper arm switching element S1 of the inverter 11 to the motor 3 and the current path from the motor 3 to the V-phase lower arm switching element S4 of the inverter 11 cannot be secured. Therefore, the U-phase current I U and V-phase current I V Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is C7.

[0297] 39A and 39B show, as an example, a break in the U-phase power line 12U and the V-phase power line 12V. Even if the V-phase power line 12V and the W-phase power line 12W are broken, or the W-phase power line 12W and the U-phase power line 12U are broken, or even if the U-phase power line 12U, the V-phase power line 12V and the W-phase power line 12W are broken, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the states of the motor drive device 1 are D6 and C7.

[0298] When command patterns Q1 to Q7 are executed, states D6 and C7 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in FIG. 14, the type and location of the fault can be determined to be a break in a power line of two or more phases.

[0299] 40A to 40C are circuit diagrams showing the state of the motor drive device when a short circuit occurs between the U-phase power line and the V-phase power line. Fig. 40A shows the state of the motor drive device operating under command pattern Q1, Fig. 40B shows the state of the motor drive device operating under command pattern Q2, and Fig. 40C shows the state of the motor drive device operating under command pattern Q3.

[0300] 40A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the U-phase power line 12U and the V-phase power line 12V are short-circuited, the current from the DC link flows through the switching element S1 to the U-phase current I U and flows to the AC side as a V-phase current I V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2), and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2”. Therefore, the state of the motor driving device 1 is E1.

[0301] 40B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the U-phase power line 12U and the V-phase power line 12V are short-circuited, the current from the DC link flows through the switching element S3 to the V-phase current I V and flows to the AC side as a U-phase current I U The U-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2, and the V-phase current I V is "V DC / ((3R DB ) / 2) is greater than the value of the reference voltage Vcc. Therefore, the state of the motor drive device 1 is E2.

[0302] 40C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. In addition, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Since the U-phase power line 12U and the V-phase power line 12V are short-circuited, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W-phase current and then flows through the dynamic braking resistor 31W and the switch 32W. WThe current flowing through the switch 32V and the dynamic braking resistor 31V is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U, and a current flowing through the switch 32V and the dynamic braking resistor 31V. The current flowing through the switch 32V and the dynamic braking resistor 31V is a V-phase current I V and a current flowing into the U-phase power line 12U via the short circuit between the U-phase power line 12U and the V-phase power line 12V. The current flowing into the U-phase power line 12U via the short circuit between the U-phase power line 12U and the V-phase power line 12V joins with the current flowing through the switch 32U and the dynamic brake resistor 31U, resulting in a U-phase current I U The U-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A3.

[0303] Once command patterns Q1 to Q3 have been executed, states E1 and E2 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in Fig. 14, it is possible to identify the type and location of the fault as a short circuit between U-phase power line 12U and V-phase power line 12V. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit between U-phase power line 12U and V-phase power line 12V.

[0304] 41A and 41B are circuit diagrams showing the state of the motor drive device when a short circuit occurs between the V-phase power line and the W-phase power line. Fig. 41A shows the state of the motor drive device operating under command pattern Q1, and Fig. 41B shows the state of the motor drive device operating under command pattern Q2.

[0305] 41A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I U The U-phase current I flows to the AC side as a U is divided into a current flowing through the switch 32V and the dynamic braking resistor 31V, and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32W and the dynamic braking resistor 31W is a W-phase current I W and a current flowing into the V-phase power line 12V via the short circuit between the V-phase power line 12V and the W-phase power line 12W. The current flowing into the V-phase power line 12V via the short circuit between the V-phase power line 12V and the W-phase power line 12W joins with the current flowing through the switch 32V and the dynamic brake resistor 31V, resulting in a V-phase current I V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0306] 41B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S3 as the V-phase current I V V-phase current I flows out to the AC side. V is a current flowing through the dynamic brake resistor 31V and the switch 32V, and a W-phase current I flowing into the W-phase power line 12W via a short circuit between the V-phase power line 12V and the W-phase power line 12W. W The current flowing through the switch 32V and the dynamic brake resistor 31V passes through the switch 32U and the dynamic brake resistor 31U and becomes the U-phase current I U The W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W flows out to the DC link through the switching element S6 of the lower arm of the W phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) is greater than the value of the reference voltage. Therefore, the state of the motor driving device 1 is F2.

[0307] When command patterns Q1 and Q2 are executed, states A1 and F2 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in Fig. 14, the type and location of the fault can be identified as a short circuit between V-phase power line 12V and W-phase power line 12W. Subsequent execution of command patterns Q3 to Q7 is not required to identify a short circuit between V-phase power line 12V and W-phase power line 12W.

[0308] 42A to 42C are circuit diagrams showing the state of the motor drive device when a short circuit occurs between the W-phase power line and the U-phase power line. Fig. 42A shows the state of the motor drive device operating under command pattern Q1, Fig. 42B shows the state of the motor drive device operating under command pattern Q2, and Fig. 42C shows the state of the motor drive device operating under command pattern Q3.

[0309] 42A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I U The U-phase current I flows out to the AC side. U is divided into a current flowing through the dynamic braking resistor 31U and the switch 32U and a current flowing through the short circuit between the W-phase power line and the U-phase power line. The current flowing through the dynamic braking resistor 31U and the switch 32U is divided into a current flowing through the switch 32V and the dynamic braking resistor 31V and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32V and the dynamic braking resistor 31V is divided into a current flowing through the V-phase current I V The current flowing through the switch 32W and the dynamic braking resistor 31W merges with the current flowing through the short circuit between the W-phase power line and the U-phase power line, and flows out to the DC link through the switching element S4 of the lower arm of the V-phase. W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2), and the V-phase current I V is "-V DC / ((3R DB) / 2) / 2". Therefore, the state of the motor driving device 1 is F1.

[0310] 42B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S3 as the V-phase current I V and flows to the AC side as a W-phase current I W The current flowing through the switch 32U and the dynamic brake resistor 31U is combined with the current flowing into the U-phase power line 12U via the short circuit between the W-phase power line 12W and the U-phase power line 12U, resulting in a U-phase current I U The U-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0311] 42C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. The dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W W-phase current I flows out to the AC side. W is divided into a current flowing through the dynamic braking resistor 31W and the switch 32W, and a current flowing through the short circuit between the W-phase power line and the U-phase power line. The current flowing through the dynamic braking resistor 31W and the switch 32W is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U, and a current flowing through the switch 32V and the dynamic braking resistor 31V. The current flowing through the switch 32V and the dynamic braking resistor 31V is divided into a current flowing through the V-phase current I V The current flowing through the switch 32U and the dynamic braking resistor 31U is combined with the current flowing through the short circuit between the W-phase power line and the U-phase power line, and flows out to the DC link through the switching element S4 of the lower arm of the V-phase. U The U-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2, and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is F3.

[0312] Once command patterns Q1 to Q3 have been executed, states F1, A2, and F3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in Fig. 14, the type and location of the fault can be identified as a short circuit between W-phase power line 12W and U-phase power line 12U. Subsequent execution of command patterns Q4 to Q7 is not required to identify a short circuit between W-phase power line 12W and U-phase power line 12U.

[0313] Figures 43A to 43C are circuit diagrams showing the state of the motor drive device when a short circuit occurs between all three-phase power lines. Figure 43A shows the state of the motor drive device operating under command pattern Q1, Figure 43B shows the state of the motor drive device operating under command pattern Q2, and Figure 43C shows the state of the motor drive device operating under command pattern Q3.

[0314] 43A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. The dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The current from the DC link flows through the switching element S1 to the U-phase current I U The U-phase current I flows out to the AC side. U is divided into a current flowing through the dynamic brake resistor 31U and the switch 32U and a current flowing toward the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line. The current flowing through the dynamic brake resistor 31U and the switch 32U is divided into a current flowing through the switch 32V and the dynamic brake resistor 31V and a current flowing through the switch 32W and the dynamic brake resistor 31W. The current flowing through the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line is divided into a current flowing toward the V-phase power line 12V and a current flowing toward the W-phase power line 12W. The current flowing through the switch 32V and the dynamic brake resistor 31V is combined with the current flowing from the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line, to form a V-phase current I VThe current flowing through the switch 32W and the dynamic braking resistor 31W is combined with the current flowing from the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line, resulting in a W-phase current I W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2), and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2”. Therefore, the state of the motor driving device 1 is E1.

[0315] 43B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. The dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The current from the DC link flows through the switching element S3 to the V-phase current I V V-phase current I flows out to the AC side. V is divided into a current flowing through the dynamic brake resistor 31V and the switch 32V and a current flowing toward the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line. The current flowing through the dynamic brake resistor 31V and the switch 32V is divided into a current flowing through the switch 32U and the dynamic brake resistor 31U and a current flowing through the switch 32W and the dynamic brake resistor 31W. The current flowing through the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line is divided into a current flowing toward the U-phase power line 12U and a current flowing toward the W-phase power line 12W. The current flowing through the switch 32U and the dynamic brake resistor 31U is combined with the current flowing from the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line, to form U-phase current I UThe current flowing through the switch 32W and the dynamic braking resistor 31W is combined with the current flowing from the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line, resulting in a W-phase current I W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2, and the V-phase current I V is "V DC / ((3R DB ) / 2) is greater than the value of the reference voltage Vcc. Therefore, the state of the motor drive device 1 is E2.

[0316] 43C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W W-phase current I flows out to the AC side. W is divided into a current flowing through the dynamic brake resistor 31W and the switch 32W and a current flowing through the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line. The current flowing through the dynamic brake resistor 31W and the switch 32W is divided into a current flowing through the switch 32U and the dynamic brake resistor 31U and a current flowing through the switch 32V and the dynamic brake resistor 31V. The current flowing through the switch 32U and the dynamic brake resistor 31U joins the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line, and becomes the U-phase current I UThe current flowing through the switch 32V and the dynamic brake resistor 31V merges with the short circuit between the U-phase power line 12U, the V-phase power line 12V, and the W-phase power line, and flows out as a V-phase current I V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2, and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2”. Therefore, the state of the motor drive device 1 is H3.

[0317] Once command patterns Q1 to Q3 have been executed, states E1, E2, and H3 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15, and it is possible to identify that the type and location of the fault is a short circuit between all three-phase power lines based on the fault determination conditions shown in Figure 14. Subsequent execution of command patterns Q4 to Q7 is not necessary to identify a short circuit between all three-phase power lines.

[0318] Figures 44A to 44D are circuit diagrams showing the state of the motor drive device when a ground fault occurs in the U-phase power line. Figure 44A shows the state of the motor drive device operating under command pattern Q1, Figure 44B shows the state of the motor drive device operating under command pattern Q2, Figure 44C shows the state of the motor drive device operating under command pattern Q3, and Figure 44D shows the state of the motor drive device operating under command pattern Q4.

[0319] 44A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I U The U-phase current I flows out to the AC side. U is divided into a current flowing through the dynamic braking resistor 31U and the switch 32U and a current flowing through the ground fault point of the U-phase power line. The current flowing through the dynamic braking resistor 31U and the switch 32U is divided into a current flowing through the switch 32V and the dynamic braking resistor 31V and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32V and the dynamic braking resistor 31V is divided into a current flowing through the V-phase current I V The current flowing through the switch 32W and the dynamic braking resistor 31W is the W-phase current I W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2), and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is F1.

[0320] 44B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. The dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S3 as the V-phase current I V The current flowing through the dynamic braking resistor 31V and the switch 32V is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U, and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32U and the dynamic braking resistor 31U is the U-phase current I U The current flowing through the switch 32W and the dynamic braking resistor 31W is divided into the W-phase current I W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) is greater than the value of the reference voltage. Therefore, the state of the motor driving device 1 is F2.

[0321] 44C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through switching element S5 to the W-phase current IW The W-phase current I flows to the AC side as a W is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V U-phase current I U The V-phase current I is divided into a current that flows out to the DC link through the switching element S1 of the lower arm of the U-phase, and a current that flows through the ground fault point of the U-phase power line. V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A3.

[0322] 44D, in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and operate ON. Therefore, the current from the DC link flows through switching element S1 as the U-phase current I U As a result, the U-phase current I U is "greater than 0", and the V-phase current I V becomes "0." Therefore, the state of the motor drive device 1 is D4.

[0323] Once command patterns Q1 to Q4 have been executed, states F1, F2, A3, and D4 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in Fig. 14, it is possible to identify that the type and location of the fault is a ground fault in the U-phase power line. Subsequent execution of command patterns Q5 to Q7 is not necessary to identify a ground fault in the U-phase power line.

[0324] Figures 45A to 45D are circuit diagrams showing the state of the motor drive device when a ground fault occurs in the V-phase power line. Figure 45A shows the state of the motor drive device operating under command pattern Q1, Figure 45B shows the state of the motor drive device operating under command pattern Q2, Figure 45C shows the state of the motor drive device operating under command pattern Q3, and Figure 45D shows the state of the motor drive device operating under command pattern Q4.

[0325] 45A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I U and flows to the AC side as a W-phase current I, and then flows into the dynamic braking resistor 31U and the switch 32U. The current flowing through the dynamic braking resistor 31U and the switch 32U is divided into a current flowing through the switch 32V and the dynamic braking resistor 31V, and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32V and the dynamic braking resistor 31V is divided into a current flowing out to the DC link via the switching element S4 of the V-phase lower arm, and a current flowing through the ground fault point of the U-phase power line. The current flowing through the switch 32W and the dynamic braking resistor 31W is divided into a W-phase current I W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. Uand V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2), and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is F1.

[0326] 45B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. The dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S3 as the V-phase current I V V-phase current I flows to the AC side. V is divided into a current flowing through the dynamic braking resistor 31V and the switch 32V and a current flowing through the ground fault point of the V-phase power line. The current flowing through the dynamic braking resistor 31V and the switch 32V is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32U and the dynamic braking resistor 31U is divided into a current flowing through the U-phase current I U The current flowing through the switch 32W and the dynamic braking resistor 31W is the W-phase current I W The U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) is greater than the value of the reference voltage. Therefore, the state of the motor driving device 1 is F2.

[0327] 45C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U, and a current flowing through the switch 32V and the dynamic braking resistor 31V. The current flowing through the switch 32U and the dynamic braking resistor 31U is the U-phase current I U The current flowing through the switch 32V and the dynamic braking resistor 31V flows to the DC link through the switching element S1 of the lower arm of the U phase as a V-phase current. When the current flowing through the switch 32V and the dynamic braking resistor 31V flows to the DC link through the switching element S4 of the lower arm of the V phase, it is divided into a current flowing through the ground fault point of the V-phase power line. V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A3.

[0328] 45D, in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. In addition, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and operate ON. Therefore, the current from the DC link flows through switching element S3 as the V-phase current I V and flows to the AC side as a ground fault point in the V-phase power line. U becomes "0", and the V-phase current I V is "greater than 0." Therefore, the state of the motor driving device 1 is E4.

[0329] Once command patterns Q1 to Q4 have been executed, states F1, F2, A3, and E4 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14, and voltage detection unit 15. Based on the fault determination conditions shown in Fig. 14, it is possible to identify that the type and location of the fault is a ground fault in the V-phase power line. Subsequent execution of command patterns Q5 to Q7 is not necessary to identify a ground fault in the V-phase power line.

[0330] Figures 46A to 46D are circuit diagrams showing the state of the motor drive device when a ground fault occurs in the W-phase power line. Figure 46A shows the state of the motor drive device operating under command pattern Q1, Figure 46B shows the state of the motor drive device operating under command pattern Q2, Figure 46C shows the state of the motor drive device operating under command pattern Q3, and Figure 46D shows the state of the motor drive device operating under command pattern Q4.

[0331] 46A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S1 as the U-phase current I U The current flowing through the dynamic braking resistor 31U and the switch 32U is divided into a current flowing through the switch 32V and the dynamic braking resistor 31V, and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32V and the dynamic braking resistor 31V is the V-phase current I V The current flowing through the switch 32W and the dynamic braking resistor 31W is the W-phase current I W The U-phase current I is divided into a current flowing out to the DC link through the switching element S6 of the lower arm of the W-phase and a current flowing through the ground fault point of the U-phase power line. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2), and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is F1.

[0332] 46B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. The dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through the switching element S3 as the V-phase current IV The current flowing through the dynamic braking resistor 31V and the switch 32V is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U, and a current flowing through the switch 32W and the dynamic braking resistor 31W. The current flowing through the switch 32U and the dynamic braking resistor 31U is the U-phase current I U The current flowing through the switch 32W and the dynamic braking resistor 31W is the W-phase current I W The U-phase current I is divided into a current flowing out to the DC link through the switching element S6 of the lower arm of the W-phase and a current flowing through the ground fault point of the W-phase power line. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) is greater than the value of the reference voltage. Therefore, the state of the motor driving device 1 is F2.

[0333] 46C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W W-phase current I flows out to the AC side. Wis divided into a current flowing through the dynamic braking resistor 31W and the switch 32W, and a current flowing through the ground fault point of the W-phase power line. The current flowing through the dynamic braking resistor 31W and the switch 32W is divided into a current flowing through the switch 32U and the dynamic braking resistor 31U, and a current flowing through the switch 32V and the dynamic braking resistor 31V. The current flowing through the switch 32U and the dynamic braking resistor 31U is divided into a current flowing through the U-phase current I U The current flowing through the switch 32V and the dynamic braking resistor 31V flows to the DC link through the switching element S1 of the lower arm of the U phase as a V-phase current. When the current flowing through the switch 32V and the dynamic braking resistor 31V flows to the DC link through the switching element S4 of the lower arm of the V phase, it is divided into a current flowing through the ground fault point of the V-phase power line. V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A3.

[0334] As shown in Figure 46D, in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3, the U-phase current I U becomes "0", and the V-phase current I Vbecomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is A4.

[0335] Figures 47A to 47G are circuit diagrams showing the states of a normal motor drive device. Figure 47A shows the state of the motor drive device operating under command pattern Q1, Figure 47B shows the state of the motor drive device operating under command pattern Q2, Figure 47C shows the state of the motor drive device operating under command pattern Q3, and Figure 47D shows the state of the motor drive device operating under command pattern Q4. Also, Figure 47E shows the state of the motor drive device operating under command pattern Q5, Figure 47F shows the state of the motor drive device operating under command pattern Q6, and Figure 47G shows the state of the motor drive device operating under command pattern Q7.

[0336] As shown in Fig. 47A, in command pattern Q1, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 as the U-phase current I U The U-phase current I flows to the AC side as a U is the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W V-phase current I V The W-phase current I flows out to the DC link through the V-phase lower arm switching element S4. WThe U-phase current I flows out to the DC link through the switching element S6 of the lower arm of the W-phase. U and V-phase current I V Calculating the U-phase current I U is "V DC / ((3R DB ) / 2) and the V-phase current I V is "-V DC / ((3R DB ) / 2) / 2". Therefore, the state of the motor driving device 1 is A1.

[0337] As shown in Figure 47B, in command pattern Q2, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The U-phase lower arm switching element S2, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S3 as the V-phase current I V The V-phase current I flows to the AC side and then flows through the dynamic brake resistor 31V and the switch 32V. V is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the W-phase current I flowing through the switch 32W and the dynamic braking resistor 31W. W U-phase current I U The W-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. W The U-phase current I flows out to the DC link through the W-phase lower arm switching element S6. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3RDB ) / 2) / 2", and the V-phase current I V is "V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A2.

[0338] As shown in Fig. 47C, in command pattern Q3, the switching command unit 17 outputs an ON command to the U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Also, the dynamic brake command unit 18 outputs a close command to close the switches 32U, 32V, and 32W. The U-phase lower arm switching element S2, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and perform an ON operation. The ON command is output for a "short time" (for example, several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S5 to the W-phase current I W The W-phase current I flows to the AC side as a W is the U-phase current I flowing through the switch 32U and the dynamic braking resistor 31U. U and the V-phase current I flowing through the switch 32V and the dynamic braking resistor 31V. V U-phase current I U The V-phase current I flows out to the DC link through the switching element S2 of the lower arm of the U-phase. V The U-phase current I flows out to the DC link through the V-phase lower arm switching element S4. U and V-phase current I V Calculating the U-phase current I U is "-V DC / ((3R DB ) / 2) / 2", and the V-phase current I V is "-V DC / ((3R DB ) / 2) Therefore, the state of the motor driving device 1 is A3.

[0339] As shown in FIG. 47D , in command pattern Q4, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Furthermore, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switches 32U, 32V, and 32W are open, no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I V becomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is A4.

[0340] As shown in FIG. 47E , in command pattern Q5, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. Furthermore, the dynamic brake command unit 18 outputs an open command, and therefore the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and turn ON. The ON command is output for a "short time" (e.g., several tens of microseconds) such that no motor current flows through the motor 3 during the ON command. Since no motor current flows through the motor 3 and the switches 32U, 32V, and 32W are open, no current flows from the DC link to the AC side via the inverter 11. Therefore, the U-phase current I U becomes "0", and the V-phase current I Vbecomes "0". Also, no overcurrent occurs in the upper arm or the lower arm of each phase of the inverter 11. Therefore, the state of the motor drive device 1 is A5.

[0341] As shown in Figure 47F, in command pattern Q6, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6. Also, the dynamic brake command unit 18 outputs an open command, and the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase upper arm switching element S3, and the W-phase lower arm switching element S6 receive the ON command and perform an ON operation. The ON command is output for a "long time" (e.g., several tens of milliseconds) that is long enough for a motor current to flow through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U and a V-phase current I V The W-phase current I from the motor 3 flows out to the AC side as a W flows out to the DC link through the switching element S6 of the lower arm of the W phase. U and V-phase current I V Calculating the U-phase current I U is "greater than 0", and the V-phase current I V is "greater than 0." Therefore, the state of the motor driving device 1 is A6.

[0342] As shown in Figure 47G, in command pattern Q7, the switching command unit 17 outputs an ON command to the U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5. In addition, the dynamic brake command unit 18 outputs an open command, so the switches 32U, 32V, and 32W are opened. The U-phase upper arm switching element S1, the V-phase lower arm switching element S4, and the W-phase upper arm switching element S5 receive the ON command and perform an ON operation. The ON command is output for a "long time" (e.g., several tens of milliseconds) that is long enough for a motor current to flow through the motor 3 during the ON command. Therefore, the current from the DC link flows through switching element S1 to the U-phase current I U and a W-phase current I W The V-phase current I from the motor 3 flows out to the AC side as a V flows out to the DC link through the switching element S4 of the lower arm of the V phase. U is "greater than 0", and the V-phase current I V is "less than 0." Therefore, the state of the motor driving device 1 is A7.

[0343] When command patterns Q1 to Q7 are executed, if states A1, A2, A3, A4, A5, A6 and A7 of motor drive device 1 are acquired based on the detection results of current detection unit 13, overcurrent detection unit 14 and voltage detection unit 15, then motor drive device 1 can be determined to be normal based on the fault determination conditions shown in Figure 14.

[0344] Advantages of the Embodiments and Modifications of the Present Disclosure According to the embodiments and modifications of the present disclosure, in a motor drive device, open circuit faults and short circuits in switching elements in an inverter, open circuit faults and short circuits in switches in a dynamic braking circuit, breaks and ground faults in power lines connecting the inverter and motor, and short circuits between power lines can be detected through a series of processes. According to the embodiments and modifications of the present disclosure, various faults can be detected through a series of processes using seven command patterns Q1 to Q7 that differ in combination of three conditions: three switching elements to be commanded to turn on in the inverter, the time at which the command is output, and open / close commands to the switches in the dynamic braking circuit. For example, a state determination process and a fault detection process can be performed each time each of the command patterns Q1 to Q7 is executed, and once the type and location of the fault have been identified through the fault detection process, the execution of subsequent command patterns can be stopped, thereby reducing the computational load associated with the fault detection process.

[0345] Because the inverter is provided with six switching elements, there are a total of six possible combinations of on / off commands for these six switching elements. However, according to the embodiment and its modified examples of the present disclosure, open faults of switching elements within the inverter, short circuits of switching elements within the inverter, open faults of switches in the dynamic braking circuit, and short circuits in the power lines can be detected using only three types of command patterns Q1 to Q3 (i.e., three possible combinations of on / off commands), which is efficient.

[0346] In addition to the three command patterns Q1 to Q3, four command patterns Q4 to Q7 are further used, which vary the time at which an ON command is output to the switching element and the open / close command to the switch of the dynamic braking circuit. This makes it possible to detect a short circuit in a switch of the dynamic braking circuit, a break in the power line, and a ground fault in the power line, thereby providing high scalability and high performance.

[0347] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments and individual variations described above. Various additions, substitutions, modifications, partial deletions, etc. are possible for these embodiments and variations within the scope of the gist of the present disclosure, or within the scope of the gist of the present disclosure derived from the content of the claims and their equivalents. These embodiments and variations can also be implemented in combination. For example, in the above-described embodiments and variations, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments and variations.

[0348] <Supplementary Notes> The following supplementary notes are further disclosed regarding the above-described embodiment and modifications.

[0349] (Supplementary Note 1) An inverter comprising a three-phase bridge circuit in which switching elements are provided in each of the upper arms on the high potential side and the lower arms on the low potential side of each of the three phases, which converts the DC voltage of the DC link into AC voltage and outputs it by switching operations of the switching elements; a power line provided between the inverter and the motor, which supplies the AC voltage output from the inverter to the motor; a current detection unit provided in the power line, which detects the value of the current output from the inverter; an overcurrent detection unit which detects the presence or absence of an overcurrent flowing in the upper arm or the lower arm; a voltage detection unit which detects the value of the DC voltage; a dynamic braking circuit connected between the current detection unit and the motor in the power line, which can short-circuit the phases of the motor windings via a resistor by closing a switch; a switching command unit which commands the switching operation of each switching element; and a dynamic braking command unit which commands the opening and closing operation of each switch. a failure detection unit that detects a failure within the motor drive device based on detection results from the current detection unit, the overcurrent detection unit, and the voltage detection unit when a switching command unit commands the switching operation of each switching element and a dynamic braking command unit commands the opening and closing operation of each switch. (Supplementary Note 2) The motor drive device according to Supplementary Note 1, wherein the fault detection unit has: a memory unit that stores a calculation formula for calculating a current reference value corresponding to each of a plurality of command patterns for the switching operation of each switching element and the opening and closing operation of each switch; a calculation unit that calculates a current reference value corresponding to the command pattern in accordance with the calculation formula stored in the memory unit using a DC voltage value detected by the voltage detection unit when the switching operation of each switching element and the opening and closing operation of each switch are commanded in accordance with the command pattern; a comparison unit that compares the current value detected by the current detection unit when the switching operation of each switching element and the opening and closing operation of each switch are commanded in accordance with the command pattern with the current reference value calculated by the calculation unit and corresponding to the command pattern; and a determination unit that determines the location and type of fault based on a comparison result by the comparison unit when the switching operation of each switching element and the opening and closing operation of each switch are commanded in accordance with the command pattern and whether or not an overcurrent is detected by the overcurrent detection unit.(Supplementary Note 3) The motor drive device according to Supplementary Note 2, wherein each of the plurality of command patterns includes information regarding an ON command and an OFF command for each switching element, information regarding the length of time for outputting the ON command for each switching element, and information regarding an OPEN command and a CLOSE command for each switch. (Supplementary Note 4) The motor drive device according to Supplementary Note 3, wherein each of the first command pattern, the second command pattern, and the third command pattern among the plurality of command patterns includes an ON command for a switching element provided in one phase of the upper arm and an OFF command for switching elements provided in two phases other than the one phase, an ON command for a switching element provided in two phases of the lower arm and an OFF command for switching elements provided in one phase other than the one phase, information regarding the length of time for outputting the ON commands, and a CLOSE command for each switch. (Supplementary Note 5) The motor drive device according to Supplementary Note 3, wherein each of a fourth command pattern and a fifth command pattern among the plurality of command patterns includes an on command for a switching element provided in two phases of the upper arm and an off command for a switching element provided in one other phase different from the two phases, an on command for a switching element provided in one phase of the lower arm and an off command for a switching element provided in the two other phases different from the one phase, information regarding the length of time for outputting the on commands, and an open command for each switch. (Supplementary Note 6) The motor drive device according to Supplementary Note 5, wherein each of a sixth command pattern and a seventh command pattern among the plurality of command patterns includes an on command for a switching element provided in two phases of the upper arm and an off command for a switching element provided in one other phase different from the two phases, an on command for a switching element provided in one phase of the lower arm and an off command for a switching element provided in the two other phases different from the one phase, information about the length of time for outputting the on commands, and an open command for each of the switches, and wherein the length of time for outputting the on commands in each of the sixth command pattern and the seventh command pattern is set to a value longer than the length of time for outputting the on commands in each of the fourth command pattern and the fifth command pattern.(Supplementary Note 7) The motor drive device according to any one of Supplementary Notes 1 to 6, wherein the fault is any one of an open fault of a switching element, a short circuit of a switching element, an open fault of a switch, a short circuit of a switch, a break in a power line, a short circuit of a power line, and a ground fault of a power line. (Supplementary Note 8) The motor drive device according to Supplementary Note 7, wherein the fault detection unit identifies the type and location of the fault according to the detection results of the current detection unit, the overcurrent detection unit, and the voltage detection unit when the switching command unit commands the switching operation of each switching element and the dynamic braking command unit commands the opening and closing operation of each switch.

[0350] REFERENCE SIGNS LIST 1 Motor drive device 2 AC power supply 3 Motor 9 Capacitor 10 Converter 11 Inverter 12U U-phase power line 12V V-phase power line 12W W-phase power line 13 Current detection unit 14 Overcurrent detection unit 15 Voltage detection unit 16 Dynamic braking circuit 17 Switching command unit 18 Dynamic braking command unit 19 Fault detection unit 21 Memory unit 22 Calculation unit 23 Comparison unit 24 Determination unit 31 Combined resistance of dynamic braking resistances 31U U-phase dynamic braking resistance 31V V-phase dynamic braking resistance 31W W-phase dynamic braking resistance 32U U-phase switch 32V V-phase switch 32W W-phase switch 61 Combined resistance of motor resistances 62 Combined inductance of motor coil 61U U-phase motor resistance 61V V-phase motor resistance 61W W-phase motor resistance 62U U-phase motor coil 62V V-phase motor coil 62W W-phase motor coil S1 U-phase upper arm switching element S2 U-phase lower arm switching element S3 V-phase upper arm switching element S4 V-phase lower arm switching element S5 W-phase upper arm switching element S6 W-phase lower arm switching element

Claims

an inverter including a three-phase bridge circuit in which a switching element is provided in each of an upper arm on a high potential side and a lower arm on a low potential side of each of the three phases, the inverter converting a DC voltage of a DC link into an AC voltage and outputting the AC voltage by switching the switching elements; a power line provided between the inverter and the motor, for supplying the AC voltage output from the inverter to the motor; a current detection unit provided on the power line and detecting a value of a current output from the inverter; an overcurrent detection unit that detects whether or not an overcurrent flows through the upper arm or the lower arm; a voltage detection unit that detects the value of the DC voltage; a dynamic braking circuit connected in the power line between the current detection unit and the motor, and capable of short-circuiting the phases of the motor windings via a resistor by closing a switch; a switching command unit that commands the switching operation of each of the switching elements; a dynamic brake command unit that commands the opening and closing operations of each of the switches; a fault detection unit that detects a fault in the motor drive device based on the detection results of the current detection unit, the overcurrent detection unit, and the voltage detection unit when the switching command unit commands the switching operation of each of the switching elements and the dynamic braking command unit commands the opening and closing operation of each of the switches; A motor drive device comprising: 　 The failure detection unit a storage unit that stores a calculation formula for calculating a current reference value corresponding to each of a plurality of command patterns for the switching operation of each of the switching elements and the opening and closing operation of each of the switches; a calculation unit that calculates the current reference value corresponding to the command pattern in accordance with the calculation formula stored in the storage unit, using a value of the DC voltage detected by the voltage detection unit when a command is issued to switch the switching elements and open / close the switches in accordance with the command pattern; a comparison unit that compares a value of a current detected by the current detection unit when a switching operation of each of the switching elements and an opening / closing operation of each of the switches are instructed in accordance with the command pattern with the current reference value calculated by the calculation unit and corresponding to the command pattern; a determination unit that determines the location and nature of the fault based on a comparison result by the comparison unit when a switching operation of each of the switching elements and an opening / closing operation of each of the switches is instructed in accordance with the command pattern and based on whether or not an overcurrent is detected by the overcurrent detection unit; The motor drive device according to claim 1 , comprising:

3. The motor drive device of claim 2, wherein each of the plurality of command patterns includes information regarding on commands and off commands for each of the switching elements, information regarding the length of time for outputting the on commands to each of the switching elements, and information regarding open commands and close commands for each of the switches.

4. The motor drive device according to claim 3, wherein each of the first command pattern, the second command pattern and the third command pattern among the plurality of command patterns includes an on command for a switching element provided in one phase of the upper arm and an off command for a switching element provided in two phases other than the one phase, an on command for a switching element provided in one of the two phases of the lower arm and an off command for a switching element provided in one phase other than the two phases, information regarding a length of time for outputting the on command, and a close command for each of the switches.

4. The motor drive device according to claim 3, wherein each of a fourth command pattern and a fifth command pattern among the plurality of command patterns includes an on command for switching elements provided in two phases of the upper arm and an off command for switching elements provided in one phase other than the two phases, an on command for switching elements provided in one phase of the lower arm and an off command for switching elements provided in the two phases other than the one phase, information regarding a length of time for outputting the on commands, and an open command for each of the switches. 　 each of a sixth command pattern and a seventh command pattern among the plurality of command patterns includes an ON command for switching elements provided in two phases of the upper arm and an OFF command for switching elements provided in one other phase different from the two phases, an ON command for switching elements provided in one phase of the lower arm and an OFF command for switching elements provided in the other two phases different from the one phase, information on the length of time for outputting the ON command, and an open command for each of the switches; 6. The motor drive device according to claim 5, wherein a length of time for outputting the ON command in each of the sixth command pattern and the seventh command pattern is set to a value longer than a length of time for outputting the ON command in each of the fourth command pattern and the fifth command pattern. 　 The motor drive device according to any one of claims 1 to 6, wherein the fault is any one of an open fault of the switching element, a short circuit of the switching element, an open fault of the switch, a short circuit of the switch, a break in the power line, a short circuit of the power line, and a ground fault of the power line.

8. The motor drive device according to claim 7, wherein the fault detection unit identifies the type and location of the fault based on detection results from the current detection unit, the overcurrent detection unit, and the voltage detection unit when the switching command unit commands the switching operation of each of the switching elements and the dynamic braking command unit commands the opening and closing operation of each of the switches.

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