Motor drive device for determining failure of preliminary charge switch

Abstract

The motor drive device includes: a pre-charging resistor that suppresses an inrush current during a pre-charging period of a capacitor provided in a DC link that is a DC output side of a converter; a pre-charging switch connected in parallel with the pre-charging resistor; a voltage detection unit that detects the value of the input voltage; an input switching unit that selectively switches a voltage input to the voltage detection unit between a first voltage, which is a voltage of the pre-charging resistor, and a second voltage, which is a voltage other than the voltage of the pre-charging resistor; and a failure determination unit that determines the presence or absence of a failure in the preliminary charging switch on the basis of the value of the voltage detected by the voltage detection unit.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a motor drive device that performs failure determination of a preparatory charging switch. BACKGROUND

[0002] A converter and an inverter are provided in a motor drive device that drives an alternating-current motor. The converter converts alternating-current electric power supplied from an alternating-current power supply into direct-current electric power and outputs. The inverter converts the direct-current electric power into alternating-current electric power for driving the motor and outputs.

[0003] Between a direct-current output side of the converter and a direct-current input side of the inverter, a capacitor having a function of suppressing a pulsation amount of the direct-current output of the converter and a function of accumulating direct-current electric power is provided. The capacitor needs to be charged in advance to a voltage of a predetermined size during a period from when a power supply of the motor drive device is turned on to when driving of the motor is started (i.e., before a power conversion operation of the inverter is started). This charging is also referred to as "preparatory charging" or "initial charging".

[0004] The preparatory charging is started from a state in which energy is not sufficiently accumulated in the capacitor, and thus a large impact current flows from the alternating-current power supply to the capacitor via the converter immediately after the power supply of the motor drive device is turned on. Therefore, a preparatory charging circuit for suppressing the impact current during the preparatory charging is provided in the motor drive device. The preparatory charging circuit is also referred to as an "initial charging circuit" or an "impact current suppression circuit".

[0005] Generally, the preparatory charging circuit has a preparatory charging resistor that suppresses the impact current and a preparatory charging switch connected in parallel with the preparatory charging resistor. In the preparatory charging, the switch is made to be in an open state and the impact current is suppressed by the preparatory charging resistor, and in a motor drive period after the preparatory charging is completed, the preparatory charging switch is made to be in a closed state and the preparatory charging resistor is bypassed.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Publication No. 2016-116432

[0009] Patent Document 2: Japanese Patent Application Publication No. H03-239163

[0010] Patent Document 3: Published International Patent Application No. WO 2013 / 018411

[0011] Patent Document 4: Japanese Patent Application Publication No. 2005-201669 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] During the motor drive period, if the preparatory charge switch normally performs the closing operation, the current flowing from the converter to the inverter flows via the preparatory charge switch. However, when the preparatory charge switch itself or its control circuitry is abnormal and the preparatory charge switch has an open-circuit failure, even during the motor drive period, the current flowing from the converter to the inverter flows via the preparatory charge resistor, and the preparatory charge resistor can overheat and catch fire or break. Therefore, a technology capable of reliably performing overheat protection of the preparatory charge circuitry is desired.

[0014] Means for solving the problem

[0015] According to one embodiment of the present disclosure, a motor drive device includes a preparatory charge resistor that suppresses an impact current of a capacitor during a preparatory charge period, the capacitor being provided to a DC link on a DC output side of a converter that converts AC power supplied from an AC power source into DC power and outputs; a preparatory charge switch that is connected in parallel to the preparatory charge resistor, is instructed to perform an opening operation during the preparatory charge period, and is instructed to perform a closing operation during a period other than the preparatory charge period, i.e., a motor drive period; a voltage detection section that detects a value of an input voltage; an input switching section that selectively switches a voltage input to the voltage detection section between a first voltage that is a voltage of the preparatory charge resistor and a second voltage that is a voltage other than the voltage of the preparatory charge resistor; and a failure determination section that determines whether the preparatory charge switch has a failure based on the value of the voltage detected by the voltage detection section. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a diagram that shows a motor drive device of a first embodiment of the present disclosure.

[0017] Figure 2 is a diagram that illustrates a waveform of a voltage detected by a voltage detection section during a motor drive period in the first embodiment of the present disclosure.

[0018] Figure 3 is a flowchart that shows an operation flow of a motor drive device of the first embodiment of the present disclosure and a modification example thereof.

[0019] Figure 4 is a diagram that shows a motor drive device of a modification example of the first embodiment of the present disclosure.

[0020] Figure 5 is a diagram that shows a motor drive device of a second embodiment of the present disclosure.

[0021] Figure 6 is a diagram that illustrates a waveform of a voltage detected by a voltage detection section during a motor drive period and an emergency stop period in the second embodiment and the third embodiment of the present disclosure.

[0022] Figure 7 This is a flowchart illustrating the operation flow of the electric motor drive device according to the second and third embodiments of this disclosure and their variations.

[0023] Figure 8 This is a diagram showing a modified example of the second embodiment of the present disclosure, of an electric motor drive device.

[0024] Figure 9 This is a diagram illustrating the electric motor drive device according to the third embodiment of this disclosure.

[0025] Figure 10 This is a diagram showing a modified example of a third embodiment of the present disclosure, of an electric motor drive device. Detailed Implementation

[0026] Hereinafter, the motor drive device for determining the fault of the pre-charging switch according to the embodiment will be described with reference to the accompanying drawings. Furthermore, in the following description, structures having the same or similar functions will be labeled with the same reference numerals. Also, repeated descriptions of these structures will sometimes be omitted. For ease of understanding, the scale of the drawings has been appropriately changed.

[0027] In the following description, a converter that transforms AC power supplied from an AC power source into DC power and outputs it is also referred to as a "rectifier," "rectifier circuit," "rectifier," or "forward converter." An inverter that transforms DC power into AC power and outputs it is also referred to as an "inverter." A "DC link" refers to the circuit section that electrically connects the DC output side of the converter to the DC input side of the inverter; it is also referred to as a "DC link section," "DC link," "DC link unit," "DC bus," or "DC intermediate circuit." The pre-charge circuit is also referred to as an "initial charge circuit" or "inrush current suppression circuit." An "open circuit fault" in the pre-charge switch refers to an abnormality where, despite a command to close the pre-charge switch, the switch remains open. "Pre-charge period" refers to the period during which pre-charge of the capacitor is performed. "Motor drive period" refers to the period during which the motor is driven by the motor drive unit. "Emergency stop period" refers to the period during which the motor drive unit stops urgently according to an emergency stop command. "Voltage of the pre-charging resistor" refers to the potential difference across the pre-charging resistor, or the voltage obtained by dividing the potential difference across the pre-charging resistor using a voltage divider resistor. "DC link voltage" refers to the voltage obtained by dividing the potential difference between the positive potential of the positive side of the DC link's positive electric field line and the negative potential of the negative electric field line using a voltage divider resistor, or the voltage difference between the positive potential of the positive side of the DC link's positive electric field line and the negative potential of the negative electric field line.

[0028] <First Embodiment of the Present Disclosure>

[0029] Figure 1 This is a diagram illustrating an electric motor drive device according to a first embodiment of the present disclosure.

[0030] In the first embodiment of this disclosure, as well as the second and third embodiments described below, an example is shown where an AC motor 3 is driven by a motor drive device 1 connected to an AC power supply 2. The number of phases of the AC power supply 2 and the motor 3 is not particularly limited to each embodiment; for example, it can be three-phase or single-phase. Examples of AC power supplies 2 include three-phase AC 400V power supplies, three-phase AC 200V power supplies, three-phase AC 600V power supplies, and single-phase AC 100V power supplies. Here, as an example, the AC power supply 2 and the motor 3 are both three-phase. Furthermore, the number of motors 3 is not particularly limited to each embodiment; there can be multiple motors, but here, as an example, there is only one motor 3. Machines equipped with motors 3 include, for example, machine tools and robots.

[0031] like Figure 1 As shown, the motor drive device 1 of the first embodiment of this disclosure includes a converter 101, an inverter 102, a capacitor 103, a motor control unit 104, a pre-charging circuit 10, a voltage detection unit 13, an input switching unit 14, a fault determination unit 15, an on / off unit 17, a first voltage divider circuit 18, a second voltage divider circuit 19, an alarm output unit 20, an on / off control unit 24, a switch control unit 31, an input switching control unit 32, and a converter control unit 33.

[0032] A switching unit 17 is provided on the AC input side of the converter 101 to switch the circuit between the AC power supply 2 and the converter 101. The switching operation of the switching unit 17 is controlled by the switching control unit 24. The closing operation of forming the circuit between the AC power supply 2 and the converter 101 is achieved by closing the contacts of the switching unit 17. The opening operation of disconnecting the circuit between the AC power supply 2 and the converter 101 is achieved by separating the contacts of the switching unit 17. The switching unit 17 is composed of, for example, an electromagnetic contactor, a relay, or a semiconductor switching element. Information related to the switching commands from the switching control unit 24 is also sent to the fault determination unit 15.

[0033] Converter 101 converts the AC power supplied from AC power source 2 via the closed switch 17 into DC power, and outputs the DC power to the DC link, which serves as the DC output side of converter 101. Figure 1 In the example shown, AC power supply 2 is a three-phase AC power supply, therefore converter 101 is constructed from a three-phase bridge circuit. If AC power supply 2 is a single-phase AC power supply, converter 101 is constructed from a single-phase bridge circuit. Examples of converter 101 include PWM switching control rectifiers, diode rectifiers, and 120-degree energizing rectifiers.Figure 1 In the example shown, converter 101 is constructed from a PWM switching control rectifier. For example, if converter 101 is constructed from a PWM switching control rectifier or a 120-degree energized rectifier, it is constructed from a bridge circuit consisting of switching elements and diodes connected in reverse parallel with them. Power conversion is performed in both AC and DC directions by controlling the switching elements to turn on and off according to drive commands received from converter control unit 33. Examples of switching elements include FETs, IGBTs, thyristors, GTOs (gate turn-off thyristors), transistors, etc., but other switching elements may also be used.

[0034] Capacitor 103 is disposed in the DC link between the DC output side of converter 101 and the DC input side of inverter 102. One end of capacitor 103 is connected to the positive power line 41P of the DC link, and the other end of capacitor 103 is connected to the negative power line 41N of the DC link. Capacitor 103 is sometimes referred to as a "DC link capacitor," "DC link capacitor," or "smoothing capacitor." Capacitor 103 has the function of suppressing the pulsation of the DC output of converter 101 and accumulating the DC power used by inverter 102 to generate AC power. Examples of capacitor 103 include electrolytic capacitors and film capacitors.

[0035] Inverter 102 is connected to the DC output side of converter 101 via capacitor 103. Inverter 102 converts the DC power in the DC link into AC power for driving motor 3 and outputs it to the AC output side of inverter 102. Inverter 102 is composed of a bridge circuit with switching elements and diodes connected in reverse parallel with them. When motor 3 is a three-phase AC motor, inverter 102 is composed of a three-phase bridge circuit; when motor 3 is a single-phase AC motor, inverter 102 is composed of a single-phase bridge circuit. Figure 1 In the example shown, motor 3 is a three-phase AC motor, therefore inverter 102 is constructed using a three-phase bridge circuit. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used. Inverter 102 controls its power conversion operation, for example, using PWM switching control. That is, inverter 102 receives drive commands (PWM switching commands) from motor control unit 104, converts DC power in the DC link into AC power, and outputs it to motor 3. Additionally, during motor regeneration, inverter 102 receives drive commands (PWM switching commands) from motor control unit 104, converts the AC power regenerated by motor 3 into DC power, and outputs it to the DC link.

[0036] The motor control unit 104 generates drive commands for controlling the speed, torque, or rotor position of the motor 3 based on the speed of the motor 3 (speed feedback), the current flowing through the windings of the motor 3 (current feedback), speed commands, torque commands, position commands, and the operating program of the motor 3. The drive commands generated by the motor control unit 104 are sent to the switching elements within the inverter 102. Furthermore, the structure of the motor control unit 104 defined here is merely an example; for instance, it may also include terms such as a position command generation unit, a speed command generation unit, a torque command generation unit, and a switching command generation unit to define the structure of the motor control unit 104.

[0037] The pre-charging circuit 10 is installed on the DC link. Figure 1 In the example shown, the pre-charging circuit 10 is located on the positive power line 41P of the DC link. As will be described later, the pre-charging circuit 10 can also be located on the negative power line 41N of the DC link.

[0038] The pre-charging circuit 10 includes a pre-charging resistor 11 and a pre-charging switch 12.

[0039] The pre-charge resistor 11 suppresses inrush current during the pre-charge of capacitor 103. The pre-charge switch 12 is connected in parallel with the pre-charge resistor 11. Examples of the pre-charge switch 12 include relays, semiconductor switching elements, etc., but other switching components are also possible. Examples of semiconductor switching elements include IGBTs, FETs, thyristors, GTOs, transistors, etc., but other switching elements are also possible.

[0040] The pre-charge switch 12 controls the opening and closing of the circuit between the converter 101 and the capacitor 103 via the control of the switch control unit 31. During the pre-charge period, the switch control unit 31 instructs the pre-charge switch 12 to open; during periods other than the pre-charge period, i.e., during motor drive, it instructs the pre-charge switch 12 to close. Information related to the opening and closing commands of the switch control unit 31 is also sent to the fault determination unit 15.

[0041] When the pre-charging switch 12 is operating normally, it selectively switches between an open state forming a circuit through the pre-charging resistor 11 and a closed state forming a short-circuit circuit without the pre-charging resistor 11. More specifically, as follows: When the switch 17 is closed under the control of the switch control unit 24 to connect the power supply to the motor drive unit 1, power is supplied from the AC power supply 2 to the motor drive unit 1, and pre-charging of the capacitor 103 begins. During the pre-charging period from when the power supply to the motor drive unit 1 is connected until the start of driving the motor 3, the switch control unit 31 instructs the pre-charging switch 12 to open, and the pre-charging switch 12 accepts this instruction and remains in the open state. Thus, during the pre-charging period, the current output from the converter 101 flows into the capacitor 103 through the pre-charging resistor 11, and the capacitor 103 is charged (pre-charging). In this way, during the pre-charging period, the current output from the converter 101 flows through the pre-charging resistor 11, thus preventing the generation of inrush current. After pre-charging begins, when capacitor 103 is charged to a predetermined charging voltage, switch control unit 31 instructs pre-charging switch 12 to close, and pre-charging switch 12 accepts the instruction and remains closed. This completes the pre-charging of capacitor 103. After pre-charging is complete, motor control unit 104 begins driving motor 3. During motor driving, current output from converter 101 flows through the closed pre-charging switch 12 to capacitor 103 and inverter 102. Inverter 102 receives the drive instruction from motor control unit 104, converts the DC power in the DC link into AC power for driving motor 3, and outputs it to the AC output side of inverter 102.

[0042] The voltage detection unit 13 detects the value of the input voltage. More specifically, the voltage detection unit 13 outputs digital data related to the value of the input voltage based on an analog waveform associated with that voltage. As described later, the voltage input to the voltage detection unit 13 can be either a first voltage or a second voltage.

[0043] The input switching unit 14 selectively switches the voltage input to the voltage detection unit 13 between a first voltage, which is the voltage of the pre-charging resistor 11, and a second voltage, which is a voltage other than the voltage of the pre-charging resistor 11. The switching operation of the input switching unit 14 is controlled by the input switching control unit 32. The input switching unit 14 is a multiplexer that selects one of two inputs and outputs the result. The input switching unit 14 is configured, for example, by an analog switch or a relay. The input switching unit 14 has a first input terminal that receives a first voltage, a second input terminal that receives a second voltage, and an output terminal that outputs one of the first voltage and the second voltage according to the switching state. Information related to the switching state of the input switching unit 14 set by the input switching control unit 32 is also sent to the fault determination unit 15.

[0044] In the first embodiment of this disclosure, the second voltage is the potential difference between the positive side potential of the positive power line 41P of the DC link and the negative side potential of the negative power line 41N of the DC link, i.e., the DC link voltage. Therefore, the voltage of the pre-charging resistor 11, which serves as the first voltage, and the DC link voltage, which serves as the second voltage, are selectively input to the voltage detection unit 13 via the input switching unit 14.

[0045] The circuit includes a first voltage divider circuit 18 for detecting the voltage of the pre-charging resistor 11 and a second voltage divider circuit 19 for detecting the DC link voltage, such that the input voltage converges to the input range of the voltage detection unit 13.

[0046] The first voltage divider circuit 18 is connected in parallel with the pre-charging resistor 11. The first voltage divider circuit 18 has at least two first voltage divider resistors 21 connected in series with each other. One of the connection points of the first voltage divider resistors 21 is connected to the first input terminal of the input switching section 14.

[0047] The second voltage divider circuit 19 is connected between the positive potential of the positive power line 41P of the DC link and the negative potential of the negative power line 41N of the DC link. The second voltage divider circuit 19 has at least two second voltage divider resistors 22 connected in series. One of the connection points of the second voltage divider resistors 22 is connected to the second input terminal of the input switching section 14.

[0048] Furthermore, voltage divider circuits for detecting the voltage of the pre-charging resistor and for detecting the DC link voltage are sometimes already provided in the motor drive device, so these existing circuits can also be used as the first voltage divider circuit 18 and the second voltage divider circuit 19. This allows for the suppression of cost increases in the motor drive device 1.

[0049] In the input switching unit 14, under the control of the input switching control unit 32, the connection destination of the input terminals of the voltage detection unit 13 is selectively switched between a first input terminal connected to one of the connection points of the first voltage divider resistors 21 and a second input terminal connected to one of the connection points of the second voltage divider resistors 22. The voltage of the pre-charging resistor 11 is divided by the first voltage divider resistors 21 to converge to the input range of the voltage detection unit 13. The DC link voltage is divided by the second voltage divider resistors 22 to converge to the input range of the voltage detection unit 13.

[0050] The voltage input to the voltage detection unit 13 is switched by the input switching unit 14, and the voltage detection unit 13 detects either the value of the voltage of the pre-charging resistor 11 or the value of the DC link voltage. For most of the motor driving period, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the DC link voltage. Furthermore, during motor driving, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11 at a predetermined frequency (e.g., once every few seconds) for a predetermined time period (e.g., several milliseconds to tens of milliseconds). Also, the values ​​given here are merely examples, and other values ​​are possible.

[0051] Data related to the DC link voltage detected by the voltage detection unit 13 is used for the control of the inverter 102 by the motor control unit 104, the control of the converter 101 by the converter control unit 33, and the control of the pre-charging switch 12 by the switch control unit 31 during pre-charging. Additionally, data related to the voltage of the pre-charging resistor 11 detected by the voltage detection unit 13 is used for fault determination processing by the fault determination unit 15 during motor operation.

[0052] The fault determination unit 15 determines whether the pre-charging switch 12 is faulty based on the voltage value detected by the voltage detection unit 13. Figure 2 This is a diagram illustrating the waveform of the voltage detected by the voltage detection unit during motor driving in the first embodiment of this disclosure. Figure 2 As an example, after time t5, the open-circuit fault of the pre-charging switch 12 continued to occur. Additionally, in relation to... Figure 2 The values ​​listed in the relevant description are just one example; other values ​​may also be used.

[0053] like Figure 2 As shown, during times 0 to t1, t2 to t3, and t4 to t6, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the DC link voltage. Therefore, during this period, the voltage detection unit 13 detects the value of the DC link voltage (represented by the thick dashed line in the figure).

[0054] Furthermore, during times t1 to t2, t3 to t4, and t6 to t7, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11. Therefore, during these periods, the voltage detection unit 13 detects the value of the voltage of the pre-charging resistor 11 (represented by a thick solid line in the figure).

[0055] Before time t5, the pre-charge switch 12 is normally closed, so the current flowing from converter 101 to inverter 102 flows through the pre-charge switch 12 and not through the pre-charge resistor 11. Therefore, during times t1 to t2 and t3 to t4, the voltage value of the pre-charge resistor 11 detected by the voltage detection unit 13 is approximately 0 volts.

[0056] When an open-circuit fault occurs continuously after time t5 in the pre-charge switch 12, the current flowing from converter 101 to inverter 102 does not flow through the pre-charge switch 12, but instead flows through the pre-charge resistor 11. Therefore, the voltage value of the pre-charge resistor 11 detected by the voltage detection unit 13 between time t6 and time t7 becomes a value that is some degree greater than 0 volts (e.g., a few volts to tens of volts). Furthermore, the value given here is merely an example, and other values ​​may also be present.

[0057] Thus, when an open-circuit fault occurs in the pre-charging switch 12 during motor operation, the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 when the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14 becomes a value greater than 0 volts. Therefore, in the first embodiment of this disclosure, if the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 is higher than a predetermined threshold when the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14 during motor operation, the fault determination unit 15 determines that the pre-charging switch 12 has malfunctioned.

[0058] As described above, information related to the switching state of the input switching unit 14 set by the input switching control unit 32 is also sent to the fault determination unit 15. Therefore, the fault determination unit 15 is able to grasp the switching state of the input switching unit 14. After confirming that the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 through the input switching unit 14, the fault determination unit 15 performs the fault determination process described above.

[0059] The threshold used in the fault determination process of the fault determination unit 15 can be set to a level that detects "voltage generated in the pre-charging resistor 11", for example, a voltage that is a certain level higher than 0 volts (e.g., a few volts to tens of volts). Regarding the threshold, it can be set by, for example, by operating the motor drive device 1 through experiments or actual applications, or by using computer simulations to appropriately consider the application environment of the motor drive device 1, the relationship between the resistance value of the pre-charging resistor 11 and the current flowing through the pre-charging circuit 10, etc. For example, when a current of 1 ampere flows through the pre-charging resistor 11 with a resistance of 10 ohms, the voltage across the pre-charging resistor 11 is 10 volts, so the voltage threshold can be set to, for example, about 4 volts. Furthermore, the value listed here is an example, and other values ​​are also possible. In addition, the threshold can be stored in a rewritable storage unit (not shown) and can be rewritten via an external device, so that even after temporarily setting the threshold, it can be changed to an appropriate value as needed.

[0060] Furthermore, during the pre-charging period, the pre-charging switch 12 remains in the open state, so current flows from the converter 101 to the capacitor 103 via the pre-charging resistor 11. Therefore, a voltage is also generated in the pre-charging resistor 11 during the pre-charging period, but this voltage is generated regardless of whether the pre-charging switch 12 is faulty, and therefore cannot be used for fault determination processing by the fault determination unit 15. Therefore, during the pre-charging period, the fault determination unit 15 stops determining whether the pre-charging switch 12 is faulty.

[0061] The determination result of the fault determination unit 15 is sent to the alarm output unit 20. If the fault determination unit 15 determines that the pre-charging switch 12 has failed, the alarm output unit 20 outputs an alarm.

[0062] The alarm output from the alarm output unit 20 is sent to the motor control unit 104, for example. The motor control unit 104 may also perform a process to stop the power conversion operation of the inverter 102 when it receives an alarm from the alarm output unit 20.

[0063] Additionally, alarms output from alarm output unit 20 and judgment results from fault determination unit 15 can also be sent to display unit (not shown). The display unit displays the judgment results from fault determination unit 15. The display unit displays, for example, "Preparatory charging switch fault" or "Preparatory charging switch normal". The display unit can be a standalone display device, a display device attached to converter 101, a display device attached to inverter 102, a display device attached to motor drive unit 1, a display device attached to a host control device (not shown) that controls motor drive unit 1, and a display device attached to personal computer and portable terminal, etc.

[0064] Additionally, alarms output from alarm output unit 20 and judgment results from fault determination unit 15 can also be sent to an audio device, for example. The audio device emits sounds such as beeps, buzzers, or ringtones. The audio device reports the judgment results of fault determination unit 15 to the operator via sound. For example, the audio device emits a sound when the standby charging switch 12 malfunctions, but does not emit a sound when the standby charging switch 12 is functioning normally.

[0065] Additionally, alarms output from alarm output unit 20 and judgment results from fault determination unit 15 can also be sent to a printer. The printer will then print out the judgment results from fault determination unit 15.

[0066] The above describes an example of reporting the determination result of the fault determination unit 15 to the operator, but these examples can also be combined appropriately. Alternatively, the determination result of the fault determination unit 15 can be stored and accumulated in memory each time it is obtained, and database-based storage can aid in fault prediction and preventative maintenance.

[0067] Based on the reported fault determination results of the fault determination unit 15, the operator can quickly and reliably determine the fault of the standby charging switch 12. If the operator can confirm that the standby charging switch 12 has failed based on the determination results of the fault determination unit 15, they can take measures such as replacing or repairing the standby charging switch 12 or the standby charging circuit 10 including the standby charging switch 12.

[0068] Figure 3 This is a flowchart illustrating the operation flow of the electric motor drive device according to the first embodiment and its variations of the present disclosure.

[0069] As described above, in the first embodiment of this disclosure, during most of the motor driving period, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the DC link voltage, but during the motor driving period, it sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11 at a predetermined frequency (e.g., once every few seconds). To determine the timing for switching the voltage input to the voltage detection unit 13 from the DC link voltage to the voltage of the pre-charging resistor 11, the input switching control unit 32 has, for example, a timer (not shown). At the point when the voltage input to the voltage detection unit 13 is set to the DC link voltage by the input switching unit 14, the timer starts counting. At the point when the timer count reaches a predetermined value (e.g., several seconds), the input switching unit 14 switches the voltage input to the voltage detection unit 13 from the DC link voltage to the voltage of the pre-charging resistor 11. The voltage input to the voltage detection unit 13 by the input switching unit 14 is set to the voltage of the pre-charging resistor 11, and at the point when the fault determination unit 15 determines that the pre-charging switch 12 is normal, the timer count is reset.

[0070] During motor drive after the pre-charging of capacitor 103 is completed, in step S101, the input switching unit 14 switches the connection destination of the input terminal of the voltage detection unit 13 from the first voltage divider circuit 18 (one of the connection points of the first voltage divider resistors 21) to the second voltage divider circuit 19 (one of the connection points of the second voltage divider resistors 22), thereby setting the voltage input to the voltage detection unit 13 to the DC link voltage. At this time, the input switching control unit 32 sets the count value of the timer to 0.

[0071] In step S102, the input switching control unit 32 increments the count value of the timer (advances the count value).

[0072] In step S103, the voltage detection unit 13 detects the value of the DC link voltage. Data related to the value of the DC link voltage detected by the voltage detection unit 13 is used by the motor control unit 104 to control the inverter 102 and by the converter control unit 33 to control the converter 101, etc.

[0073] In step S104, the input switching control unit 32 determines whether the count value of the timer has reached a predetermined value.

[0074] If it is determined in step S104 that the timer count value has not reached the predetermined value, return to step S102.

[0075] If it is determined in step S104 that the count value of the timer has reached a predetermined value, in step S105, the input switching unit 14 switches the connection destination of the input terminal of the voltage detection unit 13 from the second voltage divider circuit 19 to the first voltage divider circuit 18, thereby setting the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11.

[0076] In step S106, the voltage detection unit 13 detects the voltage value of the pre-charging resistor 11. Data related to the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 is sent to the fault determination unit 15.

[0077] In step S107, the fault determination unit 15 determines whether the voltage of the pre-charging resistor 11 detected by the voltage detection unit 13 is higher than a predetermined threshold.

[0078] If, in step S107, the voltage of the pre-charging resistor 11 is not determined to be higher than the threshold, in step S108, the fault determination unit 15 determines that the pre-charging switch 12 is normal. In step S109, the input switching unit 14 switches the connection destination of the input terminal of the voltage detection unit 13 from the first voltage divider circuit 18 to the second voltage divider circuit 19, thereby setting the voltage input to the voltage detection unit 13 to the DC link voltage. In step S110, the input switching control unit 32 resets the timer's count value to 0, and then returns to step S102.

[0079] If, in step S107, it is determined that the voltage of the pre-charging resistor 11 is higher than the threshold, in step S111, the fault determination unit 15 determines that the pre-charging switch 12 has an open-circuit fault. In step S112, the alarm output unit 20 outputs an alarm, and then the process ends.

[0080] Figure 4 This is a diagram showing a modified example of an electric motor drive device according to the first embodiment of the present disclosure.

[0081] exist Figure 1 In the example shown, the pre-charging circuit 10 is placed on the positive power line 41P of the DC link, but in this modified example, as... Figure 4 As shown, the pre-charging circuit 10 is installed on the negative side power line 41N of the DC link.

[0082] The electric motor drive device 1 of the first embodiment of this disclosure comprises the following components: converter 101, inverter 102, capacitor 103, motor control unit 104, voltage detection unit 13, fault determination unit 15, switching unit 17, first voltage divider circuit 18, second voltage divider circuit 19, alarm output unit 20, switch control unit 31, input switching control unit 32, and converter control unit 33, as per the description. Figures 1 to 3 As illustrated in the first embodiment.

[0083] like Figure 4As shown, the pre-charging circuit 10 includes a pre-charging resistor 11 and a pre-charging switch 12. The pre-charging switch 12 is connected in parallel with the pre-charging resistor 11. During the pre-charging period from the power supply of the motor drive unit 1 to the start of the drive of the motor 3, the switch control unit 31 instructs the pre-charging switch 12 to open, and the pre-charging switch 12 accepts the instruction and remains in the open state. Thus, during the pre-charging period, a current path is formed consisting of the positive DC terminal of the converter 101, the positive power line 41P of the DC link, the capacitor 103, the pre-charging resistor 11 on the negative power line 41N of the DC link, and the negative DC terminal of the converter 101. During the pre-charging period, the current flowing from the negative terminal of the capacitor 103 flows through the pre-charging resistor 11, thus preventing the generation of inrush current. After the pre-charging begins, when the capacitor 103 is charged to a predetermined charging voltage, the switch control unit 31 instructs the pre-charging switch 12 to close, and the pre-charging switch 12 accepts the instruction and remains in the closed state. Thus, the pre-charging of capacitor 103 is completed. After the pre-charging is completed, the motor control unit 104 begins to drive the motor 3. During motor driving, if the pre-charging switch 12 operates normally, it remains closed, so no current flows through the pre-charging resistor 11.

[0084] <Second Embodiment of the Present Disclosure>

[0085] Figure 5 This is a diagram illustrating the electric motor drive device according to the second embodiment of this disclosure.

[0086] In reference Figures 1 to 4 In the first embodiment and its variations described herein, the second voltage input to the voltage detection unit 13 is set as the DC link voltage. In the second embodiment and its variations of this disclosure, the second voltage input to the voltage detection unit 13 is set as the voltage to ground, which is the potential difference between one of the positive potential of the positive side of the positive power line 41P and the negative potential of the negative power line 41N of the DC link and the ground potential (ground wire potential).

[0087] like Figure 5 As shown, the motor drive device 1 of the second embodiment of this disclosure includes a converter 101, an inverter 102, a capacitor 103, a motor control unit 104, a pre-charging circuit 10, a voltage detection unit 13, an input switching unit 14, a fault determination unit 15, an insulation status detection unit 16, an on / off unit 17, a first voltage divider circuit 18, a second voltage divider circuit 19, an alarm output unit 20, an on / off control unit 24, a switch control unit 31, an input switching control unit 32, and a converter control unit 33.

[0088] Regarding the components of the motor drive device 1 according to the second embodiment of this disclosure, including the converter 101, inverter 102, capacitor 103, motor control unit 104, first voltage divider circuit 18, alarm output unit 20, switch control unit 31, and converter control unit 33, as per [the relevant information]... Figure 1 As illustrated in the first embodiment.

[0089] exist Figure 5 In the example shown, the pre-charging circuit 10 is located on the positive power line 41P of the DC link. Regarding the operation of the pre-charging circuit 10, see the section on... Figure 1 As illustrated in the first embodiment, the pre-charging circuit 10 can also be provided on the negative side power line 41N of the DC link, as will be described later.

[0090] In the second embodiment of this disclosure, where the pre-charging circuit 10 is provided on the positive side power line 41P of the DC link, the second voltage is the potential difference between the positive side potential of the positive side power line 41P of the DC link and the ground potential (ground wire potential), i.e., the voltage to ground. Therefore, the voltage of the pre-charging resistor 11, which is the first voltage, and the voltage to ground, which is the second voltage, are selectively input to the voltage detection unit 13 via the input switching unit 14.

[0091] The circuit includes a first voltage divider circuit 18 for detecting the voltage of the pre-charging resistor 11 and a second voltage divider circuit 19 for detecting the voltage to ground, such that the input voltage converges to the input range of the voltage detection unit 13.

[0092] Regarding the first voltage divider circuit 18, as regarding Figure 1 As illustrated in the first embodiment, one of the connection points of the first voltage divider resistors 21 is connected to the first input terminal of the input switching unit 14.

[0093] Since the pre-charging circuit 10 is located on the positive power line 41P of the DC link, the second voltage divider circuit 19 is connected between the positive potential and the ground potential on the positive power line 41P of the DC link. The second voltage divider circuit 19 has at least two second voltage divider resistors 22 connected in series. One of the connection points of the second voltage divider resistors 22 is connected to the second input terminal of the input switching section 14.

[0094] Furthermore, voltage divider circuits for detecting the voltage of the pre-charging resistor and for detecting the voltage to ground are sometimes already provided in the motor drive device, so these existing circuits can also be used as the first voltage divider circuit 18 and the second voltage divider circuit 19. As a result, the cost increase of the motor drive device 1 can be suppressed.

[0095] In the input switching unit 14, under the control of the input switching control unit 32, the connection destination of the input terminals of the voltage detection unit 13 is selectively switched between a first input terminal connected to one of the connection points of the first voltage divider resistors 21 and a second input terminal connected to one of the connection points of the second voltage divider resistors 22. The voltage of the pre-charging resistor 11 is divided by the first voltage divider resistors 21 to converge to the input range of the voltage detection unit 13. The voltage to ground is divided by the second voltage divider resistors 22 to converge to the input range of the voltage detection unit 13.

[0096] The voltage input to the voltage detection unit 13 is switched by the input switching unit 14. The voltage detection unit 13 detects either the value of the voltage of the pre-charging resistor 11 or the value of the voltage to ground (the potential difference between the positive side potential of the DC link and the ground potential). During motor operation, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11. Additionally, if an emergency stop is indicated during motor operation, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage to ground. An emergency stop command for the motor 3 occurs, for example, when a malfunction occurs in the motor drive unit 1 or its associated device, or when the operator operates the emergency stop button.

[0097] Data related to the voltage to ground detected by the voltage detection unit 13 is used for insulation status detection processing of the motor 3, which is performed when an emergency stop is indicated. Additionally, data related to the voltage of the pre-charging resistor 11 detected by the voltage detection unit 13 is used for fault determination processing performed by the fault determination unit 15 during motor operation.

[0098] The insulation condition detection unit 16 detects the insulation condition of the motor 3. When an emergency stop is indicated for the motor 3, the insulation condition detection unit 16 performs the insulation condition detection process. When an emergency stop is indicated for the motor 3, the motor control unit 104 performs the process of stopping the motor 3 on the inverter 102, and the switching control unit 24 instructs the switching unit 17 to disconnect. A resistor (not shown) is provided between the winding of the motor 3 and the ground potential of the inverter 102, forming a closed circuit between the resistor, the capacitor 103, the second voltage divider circuit 19, and the ground potential. When the power from the AC power supply 2 is cut off by the switching unit 17 in the open state and the motor 3 has stopped, the residual charge of the capacitor 103 flows through the closed circuit. In the insulation condition detection process of the insulation condition detection unit 16, the DC link voltage, the potential difference between the winding of the motor 3 and the negative power line 41N of the DC link, and the voltage to ground are detected at this time. The voltage to ground is detected by the voltage detection unit 13. The DC link voltage and the potential difference between the winding of motor 3 and the negative power line 41N of the DC link are detected by different voltage detection units (not shown). The insulation condition detection unit 16 detects the insulation resistance value of motor 3 based on a known calculation formula, according to the DC link voltage, the potential difference between the winding of motor 3 and the negative power line 41N of the DC link, and the voltage to ground detected by the voltage detection unit 13.

[0099] Data related to the insulation resistance value of the motor 3 calculated by the insulation condition detection unit 16 is sent to the display unit (not shown). The display unit displays the insulation resistance value of the motor 3. The display unit may include a standalone display device, a display device attached to the converter 101, a display device attached to the inverter 102, a display device attached to the motor drive device 1, a display device attached to the upper control device (not shown) that controls the motor drive device 1, and a display device attached to a personal computer and portable terminal, etc.

[0100] Normally, the windings of motor 3 are insulated from the motor housing. However, due to years of deterioration and the infiltration of cutting fluid, the insulation performance deteriorates. Sometimes, the motor drive current flows through the housing to the grounding wire, causing the motor to become grounded. As a result, there is a risk that the residual current circuit breaker in the factory where motor 3 is installed may trip, causing the machinery equipped with motor 3 to stop, or that the operator may be electrocuted. The operator can monitor the deterioration of the insulation performance of motor 3 based on the insulation resistance value of motor 3 detected by insulation condition detection unit 16. By recognizing the signs of insulation deterioration based on the insulation resistance value of motor 3 and taking countermeasures such as replacing the motor in advance, the operator can mitigate the above-mentioned risks.

[0101] During the process of detecting the insulation status of the motor 3 by the insulation status detection unit 16, the switching unit 17, under the control of the switching control unit 24, sets the circuit between the AC power supply 2 and the converter 101 to an open state, and the input switching unit 14, under the control of the input switching control unit 32, sets the voltage input to the voltage detection unit 13 to the voltage to ground. As a result, the motor drive unit 1 is electrically disconnected from the AC power supply 2, and therefore no current flows through the pre-charging resistor 11. Therefore, the voltage of the pre-charging resistor 11 is approximately 0 volts, which does not affect the voltage detection unit 13's detection of the voltage to ground value.

[0102] In addition, during motor driving and pre-charging, the switching unit 17 sets the circuit between the AC power supply 2 and the converter 101 to a closed state under the control of the switching control unit 24, and the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11 under the control of the input switching control unit 32.

[0103] Figure 6 This is a diagram illustrating the waveforms of the voltage detected by the voltage detection unit during motor driving and emergency stop in the second and third embodiments of this disclosure. Figure 6 The waveform shown can be applied to both the second and third embodiments of this disclosure. Figure 6 As an example, the following example is shown: During the motor drive at time 0, motor 3 is stopped urgently at time t1; the emergency stop of motor 3 is lifted at time t2; during the period from time t2 to time t3, pre-charging is performed on capacitor 103; during the motor drive restarting at time t3, the pre-charging switch 12 continuously experiences an open-circuit fault after time t4. Furthermore, in conjunction with... Figure 6 The values ​​listed in the relevant description are just one example; other values ​​may also be used.

[0104] like Figure 6 As shown, from time 0 to time t1, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11. Therefore, during this period, the voltage detection unit 13 detects the value of the voltage of the pre-charging resistor 11 (represented by a thick solid line in the figure). The pre-charging switch 12 normally closes, so the current flowing from the converter 101 to the inverter 102 flows through the pre-charging switch 12 and not through the pre-charging resistor 11. Therefore, from time 0 to time t1, the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 is almost 0 volts.

[0105] When motor 3 stops urgently at time t1, the switching unit 17, under the control of the switching control unit 24, sets the circuit between AC power supply 2 and converter 101 to an open state, and the input switching unit 14, under the control of the input switching control unit 32, sets the voltage input to voltage detection unit 13 to ground voltage. During the emergency period from time t1 to time t2, voltage detection unit 13 detects the value of ground voltage (represented by a thick dashed line in the figure). During the emergency stop, insulation status detection unit 16 detects the insulation status of motor 3.

[0106] When the emergency stop of motor 3 is released at time t2, the switching unit 17, under the control of the switching control unit 24, sets the circuit between AC power supply 2 and converter 101 to a closed state, and the switch control unit 31 instructs the pre-charging switch 12 to open during the pre-charging period. At this time, the pre-charging switch 12 normally opens, so the current output from converter 101 flows through pre-charging resistor 11 to capacitor 103, and capacitor 103 is charged (pre-charging). In addition, the input switching unit 14, under the control of the input switching control unit 32, sets the voltage input to voltage detection unit 13 to the voltage of pre-charging resistor 11. During the pre-charging period, the current output from converter 101 flows through pre-charging resistor 11, thus generating a voltage in pre-charging resistor 11. Therefore, during the pre-charging period from time t2 to time t3, voltage detection unit 13 detects the value of the voltage of pre-charging resistor 11 (represented by a thick solid line in the figure). During the pre-charging period, the voltage of the pre-charging resistor 11 is generated regardless of whether the pre-charging switch 12 is faulty, and therefore cannot be used for fault determination processing performed by the fault determination unit 15. Therefore, during the pre-charging period, the fault determination unit 15 stops determining whether the pre-charging switch 12 is faulty.

[0107] When the pre-charging of capacitor 103 is completed at time t3, motor control unit 104 starts driving motor 3. During this period, switching unit 17 also sets the circuit between AC power supply 2 and converter 101 to a closed state under the control of switching control unit 24, and input switching unit 14 sets the voltage input to voltage detection unit 13 to the voltage of pre-charging resistor 11 under the control of input switching control unit 32. From time t3 to time t4, pre-charging switch 12 closes normally, so the current flowing from converter 101 to inverter 102 flows through pre-charging switch 12 and not through pre-charging resistor 11. Therefore, from time t3 to time t4, the voltage value of pre-charging resistor 11 detected by voltage detection unit 13 is approximately 0 volts.

[0108] When the open-circuit fault of the pre-charge switch 12 continues to occur after time t4, the current flowing from the converter 101 to the inverter 102 does not flow through the pre-charge switch 12, but flows through the pre-charge resistor 11. Therefore, after time t4, the voltage value of the pre-charge resistor 11 detected by the voltage detection unit 13 becomes a value that is a certain degree greater than 0 volts (e.g., a few volts to tens of volts).

[0109] Thus, when an open-circuit fault occurs in the pre-charging switch 12 during motor operation, the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 when the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14 becomes a value greater than 0 volts. Therefore, even in the second embodiment of this disclosure, similarly to the first embodiment, if the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 is higher than a predetermined threshold when the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14 during motor operation, the fault determination unit 15 determines that the pre-charging switch 12 has failed. Regarding the threshold used in the fault determination process performed by the fault determination unit 15, see [reference needed]. Figure 2 As described in the first embodiment.

[0110] Furthermore, in the second embodiment, information related to the switching state of the input switching unit 14 set by the input switching control unit 32 is also sent to the fault determination unit 15. Therefore, the fault determination unit 15 is able to grasp the switching state of the input switching unit 14. After confirming that the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 through the input switching unit 14, the fault determination unit 15 performs the aforementioned fault determination process.

[0111] Figure 7 This is a flowchart illustrating the operation flow of the electric motor drive device according to the second and third embodiments of this disclosure and their variations. Figure 7 The flowchart shown can be applied to any of the second and third embodiments of this disclosure and their variations.

[0112] In step S201, the input switching control unit 32 determines whether it is during motor drive.

[0113] If it is determined in step S201 that it is during motor driving, in step S202, the input switching unit 14 switches the connection destination of the input terminal of the voltage detection unit 13 from the second voltage divider circuit 19 (one of the connection points of the second voltage divider resistors 22) to the first voltage divider circuit 18 (one of the connection points of the first voltage divider resistors 21), thereby setting the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11.

[0114] In step S203, the voltage detection unit 13 detects the voltage value of the pre-charging resistor 11.

[0115] In step S204, the motor control unit 104 determines whether an emergency stop for the motor 3 has been instructed.

[0116] In step S204, if it is determined that an emergency stop is required for the motor 3, the motor control unit 104 performs process 102 to stop the motor 3. In step S205, the switching unit 17 performs a disconnection operation under the control of the switching control unit 24, cutting off the power supply from the AC power source 2 to the converter 101.

[0117] In step S206, the input switching unit 14 switches the connection destination of the input terminal of the voltage detection unit 13 from the first voltage divider circuit 18 to the second voltage divider circuit 19, thereby setting the voltage input to the voltage detection unit 13 as the voltage to ground.

[0118] In step S207, the voltage detection unit 13 detects the value of the voltage to ground.

[0119] In step S208, the insulation status detection unit 16 detects the insulation resistance value of the motor 3 based on the DC link voltage, the potential difference between the winding of the motor 3 and the negative power line 41N of the DC link, and the voltage to ground detected by the voltage detection unit 13.

[0120] In step S209, the motor control unit 104 determines whether the emergency stop of the motor 3 has been lifted.

[0121] If it is determined in step S209 that the emergency stop of motor 3 has been released, in step S210, the opening and closing unit 17 performs a closing action under the control of the opening and closing control unit 24, and supplies power from the AC power supply 2 to the converter 101 (power is turned on).

[0122] In step S211, the switch control unit 31 instructs the pre-charging switch 12 to disconnect. At this point, the pre-charging switch 12 disconnects normally, so the current output from the converter 101 flows into the capacitor 103 through the pre-charging resistor 11, and the capacitor 103 is charged (pre-charging). After the pre-charging of the capacitor 103 is completed, the process returns to step S201.

[0123] On the other hand, if it is not determined in step S204 that an emergency stop has been indicated for the motor 3, in step S212, the fault determination unit 15 determines whether the voltage of the pre-charging resistor 11 detected by the voltage detection unit 13 is higher than a predetermined threshold.

[0124] If the voltage of the pre-charging resistor 11 is not determined to be higher than the threshold in step S212, the fault determination unit 15 determines that the pre-charging switch 12 is normal in step S213. Then, it returns to step S201.

[0125] If, in step S212, it is determined that the voltage of the pre-charging resistor 11 is higher than the threshold, in step S214, the fault determination unit 15 determines that an open-circuit fault has occurred in the pre-charging switch 12. In step S215, the alarm output unit 20 outputs an alarm, and then the process ends.

[0126] Figure 8 This is a diagram showing a modified example of the second embodiment of the present disclosure, of an electric motor drive device.

[0127] exist Figure 5 In the example shown, the pre-charging circuit 10 is placed on the positive power line 41P of the DC link, but in this modified example, as... Figure 8 As shown, the pre-charging circuit 10 is disposed on the negative side power line 41N of the DC link. The pre-charging circuit 10 includes a pre-charging resistor 11 and a pre-charging switch 12. The pre-charging switch 12 is connected in parallel with the pre-charging resistor 11. Regarding the operation of the pre-charging circuit 10, see the section on... Figure 4 As illustrated in the modified example of the first embodiment shown.

[0128] The electric motor drive device 1 of the second embodiment of this disclosure comprises the following components: converter 101, inverter 102, capacitor 103, motor control unit 104, voltage detection unit 13, fault determination unit 15, switching unit 17, first voltage divider circuit 18, alarm output unit 20, switch control unit 31, input switching control unit 32, and converter control unit 33. Figures 5 to 7 As illustrated in the second embodiment.

[0129] In this modified example, the pre-charging circuit 10 is provided on the negative side power line 41N of the DC link. Therefore, the second voltage is the potential difference between the negative side potential of the negative side power line 41N of the DC link and the ground potential (ground wire potential), i.e., the voltage to ground. Therefore, the voltage of the pre-charging resistor 11 as the first voltage and the voltage to ground as the second voltage are selectively input to the voltage detection unit 13 via the input switching unit 14.

[0130] The circuit includes a first voltage divider circuit 18 for detecting the voltage of the pre-charging resistor 11 and a second voltage divider circuit 19 for detecting the voltage to ground, such that the input voltage converges to the input range of the voltage detection unit 13.

[0131] Regarding the first voltage divider circuit 18, as regarding Figure 1As illustrated in the first embodiment, one of the connection points of the first voltage divider resistors 21 is connected to the first input terminal of the input switching unit 14.

[0132] The second voltage divider circuit 19 is connected between the negative potential and the ground potential in the negative power line 41N of the DC link. The second voltage divider circuit 19 has at least two second voltage divider resistors 22 connected in series. One of the connection points of the second voltage divider resistors 22 is connected to the second input terminal of the input switching section 14.

[0133] In the input switching unit 14, under the control of the input switching control unit 32, the connection destination of the input terminals of the voltage detection unit 13 is selectively switched between a first input terminal connected to one of the connection points of the first voltage divider resistors 21 and a second input terminal connected to one of the connection points of the second voltage divider resistors 22. The voltage of the pre-charging resistor 11 is divided by the first voltage divider resistors 21 to converge to the input range of the voltage detection unit 13. The voltage to ground is divided by the second voltage divider resistors 22 to converge to the input range of the voltage detection unit 13.

[0134] The voltage input to the voltage detection unit 13 is switched by the input switching unit 14. The voltage detection unit 13 detects either the voltage value of the pre-charging resistor 11 or the voltage to ground (the potential difference between the negative side potential of the DC link and the ground potential). During motor operation, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage of the pre-charging resistor 11. Furthermore, in the event of an emergency stop instruction during motor operation, the input switching unit 14 sets the voltage input to the voltage detection unit 13 to the voltage to ground.

[0135] <Third Embodiment of this Disclosure>

[0136] Figure 9 This is a diagram illustrating the electric motor drive device according to the third embodiment of this disclosure.

[0137] In the third embodiment of this disclosure, similar to the second embodiment, the second voltage input to the voltage detection unit 13 is set as the voltage between ground and the ground. This voltage between ground and the ground is the potential difference between the positive potential in the positive power line 41P of the DC link and the negative potential in the negative power line 41N and the ground potential (ground wire potential).

[0138] like Figure 9As shown, the motor drive device 1 of the third embodiment of this disclosure includes a converter 101, an inverter 102, a capacitor 103, a motor control unit 104, a pre-charging circuit 10, a voltage detection unit 13, an input switching unit 14, a fault determination unit 15, an insulation status detection unit 16, an on / off unit 17, a first voltage divider circuit 18, a second voltage divider circuit 19, an alarm output unit 20, an on / off control unit 24, a switch control unit 31, an input switching control unit 32, and a converter control unit 33.

[0139] Regarding the components of the motor drive device 1 according to the third embodiment of this disclosure, including the converter 101, inverter 102, capacitor 103, motor control unit 104, pre-charging circuit 10, alarm output unit 20, switch control unit 31, and converter control unit 33, as per [the relevant information]... Figure 1 As described in the first embodiment shown. Regarding the voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, switching unit 17, second voltage divider circuit 19, switching control unit 24, and input switching control unit 32, as per the description of... Figure 5 As illustrated in the second embodiment.

[0140] exist Figure 9 In the example shown, the pre-charging circuit 10 is disposed on the positive power line 41P of the DC link. The pre-charging circuit 10 includes a pre-charging resistor 11 and a pre-charging switch 12. The pre-charging switch 12 is connected in parallel with the pre-charging resistor 11. Regarding the operation of the pre-charging circuit 10, see the section on... Figure 1 As illustrated in the first embodiment, the pre-charging circuit 10 can also be provided on the negative side power line 41N of the DC link, as will be described later.

[0141] In the third embodiment of this disclosure, where the pre-charging circuit 10 is provided on the positive side power line 41P of the DC link, the second voltage is the potential difference between the positive side potential of the positive side power line 41P of the DC link and the ground potential (ground wire potential), i.e., the voltage to ground. Therefore, the voltage of the pre-charging resistor 11, which is the first voltage, and the voltage to ground, which is the second voltage, are selectively input to the voltage detection unit 13 via the input switching unit 14.

[0142] The circuit includes a first voltage divider circuit 18 for detecting the voltage of the pre-charging resistor 11 and a second voltage divider circuit 19 for detecting the voltage to ground, such that the input voltage converges to the input range of the voltage detection unit 13.

[0143] Regarding the first voltage divider circuit 18, as regarding Figure 1 As illustrated in the first embodiment, one of the connection points of the first voltage divider resistors 21 is connected to the first input terminal of the input switching unit 14.

[0144] The second voltage divider circuit 19 is connected between the positive potential and the ground potential in the positive power line 41P of the DC link. The second voltage divider circuit 19 has at least two second voltage divider resistors 22 connected in series. One of the connection points of the second voltage divider resistors 22 is connected to the second input terminal of the input switching section 14.

[0145] Furthermore, voltage divider circuits for detecting the voltage of the pre-charging resistor and for detecting the voltage to ground are sometimes already provided in the motor drive device, so these existing circuits can also be used as the first voltage divider circuit 18 and the second voltage divider circuit 19. As a result, the cost increase of the motor drive device 1 can be suppressed.

[0146] The input switching unit 14 includes a ground voltage detection switch 42 for opening and closing the circuit connecting the second voltage divider resistors 22. The ground voltage detection switch 42 only needs to be set to the position where the circuit connecting the second voltage divider resistors 22 is open or closed. Figure 9 In the example shown, the second voltage divider resistor 22 is positioned between the second voltage divider resistor 22 and the ground potential. As another example, the voltage detection switch 42 can be positioned between the second voltage divider resistors 22, or it can be positioned between the positive potential of the positive power line 41P in the DC link and the second voltage divider resistor 22.

[0147] The voltage detection switch 42 between input and ground in the input switching unit 14 is opened and closed under the control of the input switching control unit 32.

[0148] During the process of detecting the insulation status of the motor 3 by the insulation status detection unit 16, the switching unit 17 sets the circuit between the AC power supply 2 and the converter 101 to an open state under the control of the switching control unit 24, and the voltage-to-ground detection switch 42 in the input switching unit 14 is closed under the control of the input switching control unit 32. As a result, the voltage input to the voltage detection unit 13 is set to the voltage-to-ground (the potential difference between the positive side potential of the DC link and the ground potential). Since the motor drive unit 1 is electrically disconnected from the AC power supply 2, current does not flow through the pre-charging resistor 11. Therefore, the voltage of the pre-charging resistor 11 is approximately 0 volts, which does not affect the voltage detection unit 13's detection of the voltage-to-ground value.

[0149] Furthermore, during motor operation and pre-charging, the switching unit 17, under the control of the switching control unit 24, sets the circuit between the AC power supply 2 and the converter 101 to a closed state, and the voltage detection switch 42 for grounding in the input switching unit 14 is opened under the control of the input switching control unit 32. As a result, the voltage input to the voltage detection unit 13 is set to the voltage of the pre-charging resistor 11.

[0150] Figure 6 The waveform shown can also be applied to the third embodiment of this disclosure.

[0151] like Figure 6 As shown, from time 0 to time t1, the circuit between the AC power supply 2 and the converter 101 is set to a closed state under the control of the on / off control unit 24, and the voltage detection switch 42 for ground in the input switching unit 14 is opened under the control of the input switching control unit 32. This sets the voltage of the pre-charging resistor 11 to the voltage input to the voltage detection unit 13. Therefore, during this period, the voltage detection unit 13 detects the value of the voltage of the pre-charging resistor 11 (represented by a thick solid line in the figure). The pre-charging switch 12 closes normally, so the current flowing from the converter 101 to the inverter 102 flows through the pre-charging switch 12 and not through the pre-charging resistor 11. Therefore, from time 0 to time t1, the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 is almost 0 volts.

[0152] When the motor 3 stops urgently at time t1, the switching unit 17, under the control of the switching control unit 24, sets the circuit between the AC power supply 2 and the converter 101 to an open state, and the ground voltage detection switch 42 in the input switching unit 14, under the control of the input switching control unit 32, closes. This sets the ground voltage to the voltage input to the voltage detection unit 13. Since the motor drive unit 1 is electrically disconnected from the AC power supply 2, no current flows through the pre-charging resistor 11. Therefore, the voltage of the pre-charging resistor 11 is approximately 0 volts, which does not affect the voltage detection unit 13's detection of the ground voltage value. During the emergency period from time t1 to time t2, the voltage detection unit 13 detects the value of the ground voltage (represented by a thick dashed line in the figure). During the emergency stop period, the insulation status detection unit 16 detects the insulation status of the motor 3.

[0153] When the emergency stop of motor 3 is released at time t2, the circuit between AC power supply 2 and converter 101 is set to a closed state under the control of switch control unit 24, and the voltage detection switch 42 for ground in input switching unit 14 is opened under the control of input switching control unit 32. This sets the voltage of the pre-charging resistor 11 to the voltage input to voltage detection unit 13. During the pre-charging period, switch control unit 31 instructs pre-charging switch 12 to open. At this time, pre-charging switch 12 normally opens, so the current output from converter 101 flows into capacitor 103 through pre-charging resistor 11, and capacitor 103 is charged (pre-charging). During the pre-charging period, the current output from converter 101 flows through pre-charging resistor 11, thus generating a voltage in pre-charging resistor 11. Therefore, during the pre-charging period from time t2 to time t3, voltage detection unit 13 detects the value of the voltage (represented by a thick solid line in the figure) of pre-charging resistor 11. During the pre-charging period, the voltage of the pre-charging resistor 11 is generated regardless of whether the pre-charging switch 12 is faulty, and therefore cannot be used for fault determination processing performed by the fault determination unit 15. Therefore, during the pre-charging period, the fault determination unit 15 stops determining whether the pre-charging switch 12 is faulty.

[0154] When the pre-charging of capacitor 103 is completed at time t3, motor control unit 104 starts driving motor 3. During this period, switching unit 17 also sets the circuit between AC power supply 2 and converter 101 to a closed state under the control of switching control unit 24, and input switching unit 14 sets the voltage input to voltage detection unit 13 to the voltage of pre-charging resistor 11 under the control of input switching control unit 32. From time t3 to time t4, pre-charging switch 12 closes normally, so the current flowing from converter 101 to inverter 102 flows through pre-charging switch 12 and not through pre-charging resistor 11. Therefore, from time t3 to time t4, the voltage value of pre-charging resistor 11 detected by voltage detection unit 13 is approximately 0 volts.

[0155] When an open-circuit fault occurs in the pre-charge switch 12 after time t4, the current flowing from the converter 101 to the inverter 102 does not flow through the pre-charge switch 12, but instead flows through the pre-charge resistor 11. Therefore, after time t4, the voltage value of the pre-charge resistor 11 detected by the voltage detection unit 13 becomes a value that is a certain degree greater than 0 volts (e.g., a few volts to tens of volts).

[0156] Thus, when an open-circuit fault occurs in the pre-charging switch 12 during motor operation, the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 when the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14 becomes a value greater than 0 volts. Therefore, in the third embodiment of this disclosure, similarly to the first and second embodiments, during motor operation, if the voltage value of the pre-charging resistor 11 detected by the voltage detection unit 13 when the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14 exceeds a predetermined threshold, the fault determination unit 15 determines that the pre-charging switch 12 has failed. Regarding the threshold used in the fault determination process performed by the fault determination unit 15, see [reference needed]. Figure 2 As described in the first embodiment.

[0157] Furthermore, even in the third embodiment, information related to the open / closed state of the voltage-to-ground detection switch 42 within the input switching unit 14, as set by the input switching control unit 32, is also sent to the fault determination unit 15. Therefore, the fault determination unit 15 can determine the open / closed state of the voltage-to-ground detection switch 42. After confirming that the voltage of the pre-charging resistor 11 is input to the voltage detection unit 13 via the input switching unit 14, the fault determination unit 15 performs the aforementioned fault determination process.

[0158] Figure 7 The flowchart shown can also be applied to the third embodiment and variations thereof of this disclosure.

[0159] In step S201, the input switching control unit 32 determines whether it is during motor drive.

[0160] If it is determined in step S201 that the circuit is in the motor driving phase, in step S202, the switching unit 17 sets the circuit between the AC power supply 2 and the converter 101 to a closed state under the control of the switching control unit 24, and the voltage detection switch 42 for grounding in the input switching unit 14 is opened under the control of the input switching control unit 32. As a result, the voltage input to the voltage detection unit 13 is set to the voltage of the pre-charging resistor 11.

[0161] In step S203, the voltage detection unit 13 detects the voltage value of the pre-charging resistor 11.

[0162] In step S204, the motor control unit 104 determines whether an emergency stop for the motor 3 has been instructed.

[0163] In step S204, if it is determined that an emergency stop is required for the motor 3, the motor control unit 104 performs a process to stop the motor 3 on the inverter 102. In step S205, the switching unit 17 performs a disconnection operation under the control of the switching control unit 24, cutting off the power supply from the AC power source 2 to the converter 101.

[0164] In step S206, the ground voltage detection switch 42 in the input switching unit 14 is closed under the control of the input switching control unit 32. This sets the ground voltage to the voltage input to the voltage detection unit 13.

[0165] In step S207, the voltage detection unit 13 detects the value of the voltage to ground.

[0166] In step S208, the insulation status detection unit 16 detects the insulation resistance value of the motor 3 based on the DC link voltage, the potential difference between the winding of the motor 3 and the negative power line 41N of the DC link, and the voltage to ground detected by the voltage detection unit 13.

[0167] In step S209, the motor control unit 104 determines whether the emergency stop of the motor 3 has been lifted.

[0168] If the emergency stop of the motor 3 is determined to be released in step S209, in step S210, the switching unit 17 performs a closing action under the control of the switching control unit 24, supplying power from the AC power source 2 to the converter 101 (power on). Additionally, the voltage detection switch 42 for grounding in the input switching unit 14 is opened under the control of the input switching control unit 32. As a result, the voltage input to the voltage detection unit 13 is set to the voltage of the pre-charging resistor 11.

[0169] In step S211, the switch control unit 31 instructs the pre-charging switch 12 to disconnect. At this point, the pre-charging switch 12 disconnects normally, so the current output from the converter 101 flows into the capacitor 103 through the pre-charging resistor 11, and the capacitor 103 is charged (pre-charging). After the pre-charging of the capacitor 103 is completed, the process returns to step S201.

[0170] On the other hand, if it is not determined in step S204 that an emergency stop has been indicated for the motor 3, in step S212, the fault determination unit 15 determines whether the voltage of the pre-charging resistor 11 detected by the voltage detection unit 13 is higher than a predetermined threshold.

[0171] If the voltage of the pre-charging resistor 11 is not determined to be higher than the threshold in step S212, the fault determination unit 15 determines that the pre-charging switch 12 is normal in step S213. Then, it returns to step S201.

[0172] If, in step S212, it is determined that the voltage of the pre-charging resistor 11 is higher than the threshold, in step S214, the fault determination unit 15 determines that an open-circuit fault has occurred in the pre-charging switch 12. In step S215, the alarm output unit 20 outputs an alarm, and then the process ends.

[0173] Figure 10 This is a diagram showing a modified example of a third embodiment of the present disclosure, of an electric motor drive device.

[0174] exist Figure 9 In the example shown, the pre-charging circuit 10 is placed on the positive power line 41P of the DC link, but in this modified example, as... Figure 10 As shown, the pre-charging circuit 10 is disposed on the negative side power line 41N of the DC link. The pre-charging circuit 10 includes a pre-charging resistor 11 and a pre-charging switch 12. The pre-charging switch 12 is connected in parallel with the pre-charging resistor 11. Regarding the operation of the pre-charging circuit 10, see the section on... Figure 4 As illustrated in the modified example of the first embodiment shown.

[0175] Regarding the components of the electric motor drive device 1 in the modified example of the third embodiment of this disclosure, such as the converter 101, inverter 102, capacitor 103, motor control unit 104, alarm output unit 20, switch control unit 31, and converter control unit 33, as per the description of... Figure 1 As described in the first embodiment shown. Regarding the voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, switching unit 17, and switching control unit 24, as per the description of... Figures 5 to 7 As illustrated in the second embodiment.

[0176] In this modified example, the pre-charging circuit 10 is provided on the negative side power line 41N of the DC link. Therefore, the second voltage is the potential difference between the negative side potential of the negative side power line 41N of the DC link and the ground potential (ground wire potential), i.e., the voltage to ground. Therefore, the voltage of the pre-charging resistor 11 as the first voltage and the voltage to ground as the second voltage are selectively input to the voltage detection unit 13 via the input switching unit 14.

[0177] The circuit includes a first voltage divider circuit 18 for detecting the voltage of the pre-charging resistor 11 and a second voltage divider circuit 19 for detecting the voltage to ground, such that the input voltage converges to the input range of the voltage detection unit 13.

[0178] Regarding the first voltage divider circuit 18, as regarding Figure 1 As illustrated in the first embodiment, one of the connection points of the first voltage divider resistors 21 is connected to the first input terminal of the input switching unit 14.

[0179] The second voltage divider circuit 19 is connected between the negative potential and the ground potential in the negative power line 41N of the DC link. The second voltage divider circuit 19 has at least two second voltage divider resistors 22 connected in series. One of the connection points of the second voltage divider resistors 22 is connected to the second input terminal of the input switching section 14.

[0180] The input switching unit 14 includes a ground voltage detection switch 42 for opening and closing the circuit connecting the second voltage divider resistors 22. The ground voltage detection switch 42 only needs to be set to the position where the circuit connecting the second voltage divider resistors 22 is open or closed. Figure 10 In the example shown, the second voltage divider resistor 22 is positioned between the second voltage divider resistor 22 and the ground potential. As another example, the voltage detection switch 42 can be positioned between the second voltage divider resistors 22, or it can be positioned between the negative potential of the negative power line 41N in the DC link and the second voltage divider resistor 22.

[0181] The voltage detection switch 42 between input and ground in the input switching unit 14 is opened and closed under the control of the input switching control unit 32.

[0182] During the process of detecting the insulation status of the motor 3 by the insulation status detection unit 16, the switching unit 17 sets the circuit between the AC power supply 2 and the converter 101 to an open state under the control of the switching control unit 24, and the voltage-to-ground detection switch 42 in the input switching unit 14 is closed under the control of the input switching control unit 32. As a result, the voltage input to the voltage detection unit 13 is set to the voltage-to-ground (the potential difference between the negative side potential of the DC link and the ground potential). Since the motor drive unit 1 is electrically disconnected from the AC power supply 2, current does not flow through the pre-charging resistor 11. Therefore, the voltage of the pre-charging resistor 11 is approximately 0 volts, which does not affect the voltage detection unit 13's detection of the voltage-to-ground value.

[0183] Furthermore, during motor operation and pre-charging, the switching unit 17, under the control of the switching control unit 24, sets the circuit between the AC power supply 2 and the converter 101 to a closed state, and the voltage detection switch 42 for grounding in the input switching unit 14 is opened under the control of the input switching control unit 32. As a result, the voltage input to the voltage detection unit 13 is set to the voltage of the pre-charging resistor 11.

[0184] <Common Aspects of the Various Embodiments and Variations of this Disclosure>

[0185] At least one processor, serving as an arithmetic processing unit, is provided within the motor drive unit 1. Examples of such arithmetic processing units include ICs, LSIs, CPUs, MPUs, and DSPs. The arithmetic processing unit includes a motor control unit 104, a voltage detection unit 13, a fault determination unit 15, an insulation status detection unit 16, an alarm output unit 20, an on / off control unit 24, a switch control unit 31, an input switching control unit 32, a converter control unit 33, and other processing units. These units are functional modules implemented, for example, by programs executed on the processor. For instance, when the motor control unit 104, voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, alarm output unit 20, on / off control unit 24, switch control unit 31, input switching control unit 32, converter control unit 33, and other processing units are constructed as programs, the functions of each unit can be realized by causing the arithmetic processing unit to operate according to the program. The programs for executing the processes in the motor control unit 104, voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, alarm output unit 20, on / off control unit 24, switch control unit 31, input switching control unit 32, converter control unit 33, and other processing units can also be provided in the form of a computer-readable recording medium such as a semiconductor memory, magnetic recording medium, or optical recording medium. Alternatively, the motor control unit 104, voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, alarm output unit 20, on / off control unit 24, switch control unit 31, input switching control unit 32, converter control unit 33, and other processing units can be implemented as semiconductor integrated circuits with programs written to implement the functions of each unit.

[0186] In addition, at least one memory, serving as a storage device, is provided within the motor drive unit 1. The memory also includes various storage sections within the motor control unit 104, voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, alarm output unit 20, on / off control unit 24, switch control unit 31, input switching control unit 32, and converter control unit 33. As the memory, examples include electrically erasable / recordable non-volatile memory such as EEPROM (registered trademark), or high-speed read / write random access memory such as DRAM or SRAM. Furthermore, the storage device may also have a structure such as HDD (hard disk drive) or SSD (solid-state drive). The memory stores programs for operating the motor control unit 104, voltage detection unit 13, fault determination unit 15, insulation status detection unit 16, alarm output unit 20, on / off control unit 24, switch control unit 31, input switching control unit 32, converter control unit 33, and other processing units. Additionally, the memory stores threshold values ​​used in the fault determination processing performed by the fault determination unit. In addition, various programs and data associated with the motor drive unit 1 are stored in the memory.

[0187] As explained above, overheat protection for the pre-charging circuit can be reliably implemented according to the various embodiments and variations thereof of this disclosure. Open-circuit faults in the pre-charging switch can be easily detected according to the various embodiments and variations thereof. Based on the fault determination results, the operator can quickly and reliably ascertain the status of the pre-charging switch within the pre-charging circuit. If the operator can confirm an open-circuit fault in the pre-charging switch based on the fault determination results, they can take measures such as replacing or repairing the pre-charging switch or the pre-charging circuit containing the pre-charging switch. Therefore, overheating caused by open-circuit faults in the pre-charging switch can be prevented, and abnormalities such as fires or damage to the pre-charging switch can be avoided.

[0188] As a prior art method for overheat protection of the pre-charging circuit, there is a method of monitoring the temperature by setting a temperature sensing element on a substrate where a pre-charging switch is provided. However, according to the prior art method using a temperature sensing element, depending on the placement of the temperature sensing element and the distance between the temperature sensing element and the pre-charging resistor, there is a possibility that the temperature detected by the temperature sensing element may deviate from the actual temperature of the pre-charging switch, or that the temperature detection by the temperature sensing element may be delayed, thus failing to provide sufficient overheat protection. In contrast, according to the various embodiments and variations of this disclosure, since fault determination is based on the voltage of the pre-charging resistor, overheating abnormalities of the pre-charging resistor can be detected quickly without relying on a temperature sensing element, and overheat protection for the pre-charging circuit can be reliably implemented.

[0189] Furthermore, to prevent the temperature detected by the temperature sensing element from deviating from the actual temperature of the pre-charging switch, there is a prior art that embeds the temperature sensing element inside the pre-charging switch. However, preparing a specially customized pre-charging switch with an embedded temperature sensing element would increase the cost of the motor drive device, and is therefore not preferred. In contrast, the embodiments and variations thereof disclosed herein do not embed the temperature sensing element in the switch, thus suppressing the increase in the cost of the motor drive device.

[0190] Furthermore, according to the first embodiment and its modifications of this disclosure, by selectively switching the voltage input to the voltage detection unit between the voltage of the pre-charging resistor and the DC link voltage, a single voltage detection unit detects the values ​​of the pre-charging resistor voltage and the DC link voltage. Therefore, compared to the case where separate voltage detection units are provided for detecting the voltage of the pre-charging resistor and for detecting the DC link voltage, the first embodiment and its modifications of this disclosure reduce the number of components, thus suppressing cost increases in the motor drive device. Additionally, since voltage divider circuits for detecting the voltage of the pre-charging resistor and for detecting the DC link voltage are sometimes already provided in the motor drive device, by using these existing circuits as the first and second voltage divider circuits in the first embodiment and its modifications of this disclosure, cost increases in the motor drive device can be further suppressed.

[0191] Furthermore, according to the second, third, and modified embodiments of this disclosure, by selectively switching the voltage input to the voltage detection unit between the voltage of the pre-charging resistor and the voltage to ground, a single voltage detection unit detects both the voltage of the pre-charging resistor and the voltage to ground. Therefore, compared to separately providing voltage detection units for detecting the voltage of the pre-charging resistor and voltage detection units for detecting the voltage to ground, the second, third, and modified embodiments of this disclosure reduce the number of components, thus suppressing cost increases in the motor drive device. Additionally, since voltage divider circuits for detecting the voltage of the pre-charging resistor and for detecting the voltage to ground are sometimes already provided in the motor drive device, by using these existing circuits as the first and second voltage divider circuits in the second and third embodiments and their modifications, cost increases in the motor drive device can be further suppressed.

[0192] The present disclosure has been described in detail above, but it is not limited to the various embodiments and modifications described above. These embodiments and modifications can be supplemented, substituted, modified, or partially deleted in various ways without departing from the spirit of the present disclosure or from the spirit of the present disclosure derived from the content described under the scope of the claimed patent protection and its equivalents. Furthermore, these embodiments and modifications can also be implemented in combination. For example, in the embodiments and modifications described above, the order of each action and the order of each process are shown as examples and are not limited thereto. The same applies to the use of numerical values ​​or mathematical formulas in the descriptions of the embodiments and modifications described above.

[0193] <Postscript>

[0194] The following notes further disclose the above-described embodiments and variations.

[0195] (Note 1)

[0196] The motor drive unit 1 includes: a pre-charging resistor 11 that suppresses inrush current in a capacitor during pre-charging, the capacitor being disposed in a DC link on the DC output side of a converter 101 that converts AC power supplied from AC power source 2 into DC power and outputs it; a pre-charging switch 12 connected in parallel with the pre-charging resistor 11, which is instructed to open during pre-charging and to close during periods other than pre-charging, i.e., during motor drive; a voltage detection unit 13 that detects the value of the input voltage; an input switching unit 14 that selectively switches the voltage input to the voltage detection unit 13 between a first voltage, which is the voltage of the pre-charging resistor 11, and a second voltage, which is a voltage other than the voltage of the pre-charging resistor 11; and a fault determination unit 15 that determines whether the pre-charging switch 12 is faulty based on the voltage value detected by the voltage detection unit 13.

[0197] (Note 2)

[0198] According to the motor drive device 1 described in Appendix 1, during motor driving, if the voltage value detected by the voltage detection unit 13 is higher than a predetermined threshold when a first voltage is input to the voltage detection unit 13 through the input switching unit 14, the fault determination unit 15 determines that the pre-charging switch 12 has malfunctioned.

[0199] (Note 3)

[0200] According to Appendix 1 or 2, the motor drive device 1, wherein the second voltage is the DC link voltage, which is the potential difference between the positive and negative sides of the DC link.

[0201] (Note 4)

[0202] According to Appendix 3, the motor drive device 1 includes: a first voltage divider circuit 18 connected in parallel with a pre-charging resistor 11, having at least two first voltage divider resistors 21 connected in series; and a second voltage divider circuit 19 connected between the positive and negative potentials of the DC link, having at least two second voltage divider resistors 22 connected in series; and an input switching unit 14 selectively switches the connection destination of the input terminal of the voltage detection unit 13 between one connection point of the first voltage divider resistors 21 and one connection point of the second voltage divider resistors 22.

[0203] (Note 5)

[0204] According to Appendix 1 or 2, the motor drive device 1, wherein the second voltage is the voltage to ground of the potential difference between the positive and negative potentials of the DC link and the ground potential.

[0205] (Note 6)

[0206] According to Appendix 5, the motor drive device 1 includes: an insulation state detection unit 16 that detects the insulation state of the driven motor; and an opening / closing unit 17 that opens / closes the circuit between the AC power supply 2 and the converter 101. During the process of detecting the insulation state of the motor by the insulation state detection unit 16, the opening / closing unit 17 sets the circuit between the AC power supply 2 and the converter 101 to an open state, and the input switching unit 14 sets the voltage input to the voltage detection unit 13 to a second voltage. During motor driving and pre-charging, the opening / closing unit 17 sets the circuit between the AC power supply 2 and the converter 101 to a closed state, and the input switching unit 14 sets the voltage input to the voltage detection unit 13 to a first voltage.

[0207] (Note 7)

[0208] According to the motor drive device 1 described in Appendix 6, during the pre-charging period, the fault determination unit 15 stops the process of determining whether the pre-charging switch 12 has a fault.

[0209] (Note 8)

[0210] According to Appendix 7, the motor drive device 1 includes: a first voltage divider circuit 18 connected in parallel with a pre-charging resistor 11, having at least two first voltage divider resistors 21 connected in series; and a second voltage divider circuit 19 connected between one of the positive and negative potentials of the DC link and a ground potential, having at least two second voltage divider resistors 22 connected in series; and an input switching unit 14 selectively switches the connection destination of the input terminal of the voltage detection unit 13 between one connection point of the first voltage divider resistors 21 and one connection point of the second voltage divider resistors 22.

[0211] (Note 9)

[0212] According to Appendix 2, the motor drive device 1 includes: a first voltage divider circuit 18 connected in parallel with a pre-charging resistor 11, having at least two first voltage divider resistors 21 connected in series; and a second voltage divider circuit 19 connected between one of the positive and negative potentials of the DC link and a ground potential, having at least two second voltage divider resistors 22 connected in series; and an input switching unit 14 having a switch 42 for detecting the voltage to ground of the circuit that connects the second voltage divider resistors 22 to each other.

[0213] (Postscript 10)

[0214] According to Appendix 2, the motor drive device 1 includes an alarm output unit 20 that outputs an alarm when the fault determination unit 15 determines that the pre-charge switch 12 has malfunctioned.

[0215] Explanation of reference numerals in the attached figures

[0216] 1. Electric motor drive device

[0217] 2 AC power supply

[0218] 3 electric motors

[0219] 10. Pre-charging circuit

[0220] 11. Preparatory charging resistor

[0221] 12 Pre-charge switch

[0222] 13 Voltage Detection Section

[0223] 14 Input Switching Unit

[0224] 15 Fault Determination Department

[0225] 16 Insulation Condition Testing Department

[0226] 17 Opening and Closing Sections

[0227] 18 First voltage divider circuit

[0228] 19 Second voltage divider circuit

[0229] 20 alarm output units

[0230] 21 First voltage divider resistor

[0231] 22 Second voltage divider resistor

[0232] 24 Opening and Closing Control Department

[0233] 31 Switch Control Section

[0234] 32 Input Switching Control Unit

[0235] 33 Converter Control Section

[0236] 41N negative side electric field line

[0237] 41P positive side power line

[0238] 42 switches for ground voltage detection

[0239] 101 Converter

[0240] 102 Inverter

[0241] 103 capacitor

[0242] 104 Motor Control Unit.

Claims

1. A motor drive device characterized by comprising: a pre-charge resistor that suppresses an inrush current of a capacitor during a pre-charge period, the capacitor being provided on a DC link on a DC output side of a converter that converts AC power supplied from an AC power source into DC power and outputs the DC power; a pre-charge switch that is connected in parallel with the pre-charge resistor, is instructed to be open during the pre-charge period, and is instructed to be closed during a motor drive period other than the pre-charge period; a voltage detection unit that detects a value of an input voltage; an input switching unit that selectively switches a voltage input to the voltage detection unit between a first voltage that is a voltage of the pre-charge resistor and a second voltage that is a voltage other than the voltage of the pre-charge resistor; and a failure determination unit that determines whether or not the pre-charge switch has a failure based on the value of the voltage detected by the voltage detection unit.

2. The motor drive device according to claim 1, characterized in that the failure determination unit determines that the pre-charge switch has a failure when the value of the voltage detected by the voltage detection unit is higher than a predetermined threshold value when the first voltage is input to the voltage detection unit by the input switching unit during the motor drive period.

3. The motor drive device according to claim 1 or 2, characterized in that the second voltage is a DC link voltage that is a potential difference between a positive side potential and a negative side potential of the DC link.

4. The motor drive device according to claim 3, characterized in that the motor drive device comprises: a first voltage dividing circuit that is connected in parallel with the pre-charge resistor, has at least two first voltage dividing resistors connected in series with each other, and a second voltage dividing circuit that is connected between the positive side potential and the negative side potential of the DC link, has at least two second voltage dividing resistors connected in series with each other, the input switching unit selectively switches a connection destination of an input terminal of the voltage detection unit between one of connection points of the first voltage dividing resistors to each other and one of connection points of the second voltage dividing resistors to each other.

5. The motor drive device according to claim 1 or 2, characterized in that the second voltage is an earth voltage that is a potential difference between one of a positive side potential and a negative side potential of the DC link and a ground potential.

6. The motor drive device according to claim 5, characterized in that the motor drive device comprises: an insulation state detection unit that detects an insulation state of a motor to be driven; and an opening and closing unit that opens and closes a circuit between the AC power source and the converter, during a period in which a process of detecting the insulation state of the motor by the insulation state detection unit is executed, the opening and closing unit sets the circuit between the AC power source and the converter to an open state, and the input switching unit sets the voltage input to the voltage detection unit to the second voltage. ​ ​ During the motor drive period and during the preparatory charge period, the opening / closing section sets a circuit between the alternating-current power supply and the converter to be in a closed state, and the input switching section sets a voltage input to the voltage detection section to be the first voltage.

7. The motor drive device according to claim 6, wherein During the preparatory charge period, the failure determination section stops processing of determining whether the preparatory charge switch has a failure.

8. The motor drive device according to claim 7, wherein The motor drive device includes: a first voltage dividing circuit connected in parallel to the preparatory charge resistor, having at least two first voltage dividing resistors connected in series to each other; and a second voltage dividing circuit connected between one of the positive side potential and the negative side potential of the DC link and the ground potential, having at least two second voltage dividing resistors connected in series to each other, The input switching section selectively switches a connection destination of an input terminal of the voltage detection section between one of connection points of the first voltage dividing resistors to each other and one of connection points of the second voltage dividing resistors to each other.

9. The motor drive device according to claim 7, wherein The motor drive device includes: a first voltage dividing circuit connected in parallel to the preparatory charge resistor, having at least two first voltage dividing resistors connected in series to each other; and a second voltage dividing circuit connected between one of the positive side potential and the negative side potential of the DC link and the ground potential, having at least two second voltage dividing resistors connected in series to each other, The input switching section has a ground-to-ground voltage detection switch that opens and closes a circuit connecting the second voltage dividing resistors to each other.

10. The motor drive device according to claim 2, wherein The motor drive device includes an alarm output section that outputs an alarm in a case where the failure determination section determines that the preparatory charge switch has a failure.

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