Motor drive device

Abstract

The present application provides a kind of motor driving device (1), with: converter (11), which converts alternating current power of alternating current input side into direct current power, and the direct current power is output to DC link;Inverter (12), it is controlled to be connected and disconnected to the switching element arranged in upper arm and lower arm, to convert the direct current power of DC link into alternating current power for driving motor;DC link voltage detection unit (13), it detects DC link voltage;DC link voltage determination unit (14), it determines whether DC link voltage exceeds voltage threshold value;Alarm signal output unit (15), it outputs alarm signal when abnormal;And switch control unit (16), it is controlled to be connected and disconnected to the switching element, wherein, in the case where alarm signal is output from alarm signal output unit (15) and DC link voltage exceeds voltage threshold value, switch control unit (16) is controlled to connect all switching elements of lower arm.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor drive device having a protection mechanism. BACKGROUND

[0002] In a motor drive device that controls driving of a motor in a machine tool, a forging press, an injection molding machine, an industrial machine, or various robots, alternating-current electric power supplied from an alternating-current power source is converted into direct-current electric power by a converter and output to a DC link, and the direct-current electric power in the DC link is converted into alternating-current electric power by an inverter, and the alternating-current electric power is supplied as motor drive electric power to a motor. The "DC link" refers to a circuit portion that electrically connects a direct-current output side of the converter and a direct-current input side of the inverter, and is also sometimes referred to as a "DC link portion", a "direct-current link", a "direct-current link portion", a "direct-current bus", or a "direct-current intermediate circuit", and the like. A DC link capacitor is provided in the DC link.

[0003] When an abnormality occurs in the motor drive device, a machine provided with the motor drive device, or an alternating-current power source that supplies electric power to the motor drive device, and the like, an alarm signal is output in the motor drive device or a higher-level control device of the motor drive device. The motor drive device causes the motor to be urgently stopped when the alarm signal is output, but at this time, energy based on a counter electromotive force is generated in the motor. The energy generated in the motor is regenerated to the alternating-current power source or to a regenerative load (regenerative resistor) provided in the DC link. However, in the case where the motor is large or the motor is rotating at high speed, the energy based on the counter electromotive force generated when the motor is urgently stopped is very large, and it is not possible to regenerate the energy to the alternating-current power source or the regenerative load. Therefore, some countermeasures are required.

[0004] For example, as described in Japanese Patent Application Publication No. H01-185186, a servo system protection device against abnormal current is known, which is characterized by including: a current command unit (102, 104) that issues a current command based on a position command and a rotational angle position information transmitted from a rotational angle position detector possessed by a servo motor; a current control unit (106) that receives the current command and generates a PWM signal; a current application control unit (110, 112, 114, 116, 118, 120) that receives the PWM signal and controls a drive current applied to the servo motor; a current detection unit (124, 126) that detects the drive current; and a phase monitoring unit (28) that receives the detected drive current information and the rotational angle position information of the servo motor, determines whether the phase of the drive current corresponds to the rotational angle position, and cuts off the PWM signal in the case where they do not correspond, wherein the current control unit receives the drive current information in addition to the current command, and transmits the PWM signal.

[0005] For example, as described in Japanese Patent Application Publication No. 09-103088, a motor drive circuit that supplies driving power to a motor is known, which is characterized in that the motor drive circuit is constituted by a differential amplifier and a resistor, and operates to supply power of a prescribed voltage to the motor, a first input of the differential amplifier is applied with a reference voltage, the resistor is connected between the differential amplifier and the motor with the motor side connected to a second input of the differential amplifier, and in the motor drive circuit, an overcurrent detection circuit is provided that detects a voltage drop value generated based on the resistor, and outputs a signal indicating that an overcurrent is flowing through the motor in the case where the voltage drop value exceeds a prescribed voltage value.

[0006] For example, as described in Japanese Patent Application Publication No. 2004-103031, an abnormality detection and diagnosis method for a servo control system is known, which is characterized in that, at the time of power-on, a state of connection of a transmission side of a plurality of detector use reception circuits is detected, and a type of actually connected detector is automatically discriminated, and in the case where a type of detector specified by a parameter is different from the actually connected detector, a parameter abnormality alarm is generated. SUMMARY

[0007] If the energy based on the counter electromotive voltage generated at the time of emergency stop of the motor is large at the time of alarm signal output, the energy cannot be completely regenerated into the AC power source or the load for regeneration, and the DC link voltage greatly increases. Therefore, sometimes a counter electromotive voltage protection circuit that consumes the energy based on the counter electromotive voltage at the time of alarm output is provided. However, even in the case where the counter electromotive voltage protection circuit is provided, if the counter electromotive voltage protection circuit malfunctions, the energy based on the counter electromotive voltage cannot be completely consumed, and thus the DC link voltage greatly increases. When the DC link voltage exceeds the withstand voltage of the DC link capacitor, the DC link capacitor is damaged (explodes), and thus it is very dangerous. Therefore, a technology that can reliably prevent a great increase in the DC link voltage due to generation of an abnormality in a motor drive device in which a converter and an inverter are connected via a DC link is desired.

[0008] According to one embodiment of the present disclosure, a motor drive device includes a converter that converts alternating-current power input from an alternating-current input side into direct-current power and outputs the direct-current power to a DC link that is a direct-current output side; an inverter that has a switching element connected in reverse parallel with a diode provided on an upper arm on a high potential side and a lower arm on a low potential side, converts the direct-current power in the DC link into alternating-current power for driving a motor and outputs the alternating-current power by turning on and off the switching elements provided on the upper arm and the lower arm; a DC link voltage detection unit that detects a DC link voltage that is a voltage between terminals of the DC link; a DC link voltage determination unit that determines whether the DC link voltage exceeds a voltage threshold value; an alarm signal output unit that outputs an alarm signal at the time of an abnormality; and a switching control unit that turns on and off the switching elements, wherein the switching control unit controls to turn on all of the switching elements of the lower arm in a case where the alarm signal is output from the alarm signal output unit and the DC link voltage is determined by the DC link voltage determination unit to exceed the voltage threshold value. BRIEF DESCRIPTION OF DRAWINGS

[0009] The application will be understood more clearly with reference to the following drawings.

[0010] Figure 1 FIG. 1 is a diagram illustrating a motor drive device of a first embodiment of the present disclosure.

[0011] Figure 2 FIG. 2 is a diagram illustrating an operation of a back electromotive voltage protection circuit in the motor drive device of the first embodiment of the present disclosure.

[0012] Figure 3 FIG. 3 is a diagram illustrating a flow of current in a case where all of the switching elements of a lower arm in the inverter are turned on in the motor drive device of the first embodiment of the present disclosure.

[0013] Figure 4 FIG. 4 is a flowchart illustrating an operation flow of the motor drive device of the first embodiment of the present disclosure.

[0014] Figure 5 FIG. 5 is a diagram illustrating a motor drive device of a second embodiment of the present disclosure.

[0015] Figure 6 FIG. 6 is a flowchart illustrating an operation flow of the motor drive device of the second embodiment of the present disclosure.

[0016] Figure 7 FIG. 7 is a diagram illustrating a motor drive device of a third embodiment of the present disclosure.

[0017] Figure 8 FIG. 8 is a flowchart illustrating an operation flow of the motor drive device of the third embodiment of the present disclosure.

[0018] Figure 9 This is a diagram illustrating a motor drive device according to a fourth embodiment of the present disclosure.

[0019] Figure 10 This is a flowchart illustrating the operation flow of the motor drive device according to the fourth embodiment of this disclosure.

[0020] Figure 11 This is a diagram illustrating a motor drive device according to the fifth embodiment of this disclosure.

[0021] Figure 12 This is a flowchart illustrating the operation flow of the motor drive device according to the fifth embodiment of this disclosure. Detailed Implementation

[0022] The motor drive device with a protection mechanism will now be described with reference to the accompanying drawings. The scale of these drawings has been appropriately altered for ease of understanding. The embodiments shown in the drawings are examples for implementation purposes and are not limited to the illustrated embodiments.

[0023] Figure 1 This is a diagram illustrating a motor drive device according to a first embodiment of the present disclosure.

[0024] As an example, the case where a motor 3 is controlled by a motor drive device 1 connected to an AC power supply 2 is shown. In the first embodiment and the second to fifth embodiments described later, the type of motor 3 is not particularly limited; for example, it can be an induction motor or a synchronous motor. Furthermore, the number of phases of the AC power supply 2 and the motor 3 is not particularly limited to the number of phases in the first embodiment and the second to fifth embodiments described later; for example, it can be three-phase or single-phase. In the illustrated example, the AC power supply 2 and the motor 3 are both three-phase. Examples of AC power supplies 2 include three-phase 400V AC power, three-phase 200V AC power, three-phase 600V AC power, and single-phase 100V AC power. Machinery equipped with the motor 3 includes, for example, machine tools, robots, forging presses, injection molding machines, industrial machinery, various electromechanical products, trams, automobiles, and aircraft.

[0025] like Figure 1 As shown, the motor drive device 1 of the first embodiment of this disclosure includes a converter 11, an inverter 12, a DC link voltage detection unit 13, a DC link voltage determination unit 14, an alarm signal output unit 15, and a switch control unit 16. In addition, the motor drive device 1 also includes a DC link capacitor 4, a back EMF protection circuit 17, a recording unit 18, a display unit 19, and an external device control unit 20.

[0026] Converter 11 is a rectifier that converts AC power input from the AC input side into DC power and outputs the DC power to the DC stage as the DC output side. In the illustrated example, the AC power supply 2 is a three-phase AC power supply, so converter 11 is composed of a three-phase full-bridge circuit. However, when single-phase AC power is supplied from the AC power supply 2, converter 11 functions as a single-phase bridge circuit. Examples of converter 11 include diode rectifiers, 120-degree energized rectifiers, and PWM switching control rectifiers. For example, when converter 11 is a diode rectifier, it is composed of a full-bridge circuit of diodes. For example, when converter 11 is a 120-degree energized rectifier and a PWM switching control rectifier, it is composed of a full-bridge circuit of switching elements and diodes connected in reverse parallel with the switching elements. Each switching element is turned on and off in response to a drive command received from a higher-level control device (not shown) to perform power conversion in both AC and DC directions. Examples of switching elements used in the converter 11 when it is a rectifier operating at 120 degrees Celsius or a rectifier operating under PWM switching control include IGBTs, FETs, thyristors, GTOs (Gate Turn-Off Thyristors), transistors, and other semiconductor components. Additionally, AC reactors, AC line filters, electromagnetic contactors, circuit breakers, etc., are sometimes provided on the AC input side of the converter 11; these are not illustrated here.

[0027] A DC link capacitor 4 is provided in the DC link connecting the DC output side of converter 11 to the DC input side of inverter 12. The DC link capacitor 4 has the functions of storing DC power used to generate AC power for inverter 12 and suppressing pulsations in the DC output of converter 11. Examples of DC link capacitor 4 include electrolytic capacitors or film capacitors. Furthermore, a regeneration load (regeneration resistor) for consuming regeneration energy from motor 3 may also be provided in the DC link.

[0028] Inverter 12 is connected to converter 11 via a DC link, converting the DC power in the DC link into AC power for driving the motor and outputting the AC power. In the illustrated example, since motor 3 is a three-phase AC motor, inverter 12 is composed of a three-phase full-bridge circuit; however, if motor 3 is a single-phase motor, inverter 12 is composed of a single-phase full-bridge circuit.

[0029] In inverter 12, switching elements with diodes connected in reverse parallel are respectively provided on the upper arm of the high-potential side and the lower arm of the low-potential side. In the illustrated example, regarding phase U, the upper arm is designated as U... U Set the lower arm to U. L Regarding the V phase, set the upper arm as V.U , the lower arm is set to V L , the upper arm is set to W U , the lower arm is set to W L . The inverter 12 controls the on and off of the switching elements provided in the upper arms U U , V U , and W U and the lower arms U L , V L , and W L , respectively, based on the instructions of the switching control section 16, for example, in a PWM control manner, thereby converting the direct current power in the DC link into alternating current power for driving the motor and outputting the alternating current power. The motor 3 is controlled in speed, torque, or position of the rotor based on the alternating current power supplied from the inverter 12. Further, the inverter 12 is also capable of regenerating the power generated in the motor 3 into the alternating current power source 2 or the DC link by the on and off actions of the switching elements, with the PWM control being appropriately performed. A load for regeneration (a resistor for regeneration) is provided in the DC link, and the energy regenerated from the motor 3 via the inverter 12 is consumed by the load for regeneration when regenerated into the DC link. As the switching elements, there are IGBT, FET, thyristor, GTO, transistor, and the like, but other semiconductor elements can also be used.

[0030] The DC link voltage detection section 13 detects the DC link voltage, which is the voltage between the terminals of the DC link. That is, the DC link voltage detection section 13 detects the value of the potential difference between the positive potential appearing at the positive terminal on the direct current output side of the converter 11 and the negative potential appearing at the negative terminal on the direct current output side of the converter 11 as the DC link voltage. Alternatively, the DC link voltage detection section 13 can also detect the voltage applied between the positive and negative terminals of the DC link capacitor 4 as the DC link voltage. The value of the DC link voltage detected by the DC link voltage detection section 13 is sent to the DC link voltage determination section 14.

[0031] The DC link voltage determination section 14 compares the DC link voltage detected by the DC link voltage detection section 13 with the voltage threshold value V th1 , and determines whether the DC link voltage exceeds the voltage threshold value. Even in the case where the motor drive device 1 normally drives the motor 3 without failure in a state where the alternating current power source 2 is not powered off (hereinafter, referred to simply as "normal state"), some pulsation is generated in the DC link voltage. The voltage threshold value V th1 is set to a value higher than the DC link voltage that rises due to the pulsation in the normal state generated when the motor 3 is driven by the motor drive device 1. As for the voltage threshold value V th1For example, the relationship between the voltage value on the DC output side of the converter 11 and the output of the alarm signal in the motor drive device 1 can be obtained in advance by experiment or actual operation, or by simulation by a computer, and based on this, the voltage threshold value Vth can be appropriately set th1 For example, the relationship between the voltage value on the DC output side of the converter 11 and the output of the alarm signal in the motor drive device 1 can be obtained in advance by experiment or actual operation, or by simulation by a computer, and based on this, the voltage threshold value Vth can be appropriately set th1 For example, the relationship between the voltage value on the DC output side of the converter 11 and the output of the alarm signal in the motor drive device 1 can be obtained in advance by experiment or actual operation, or by simulation by a computer, and based on this, the voltage threshold value Vth can be appropriately set th1 For example, the relationship between the voltage value on the DC output side of the converter 11 and the output of the alarm signal in the motor drive device 1 can be obtained in advance by experiment or actual operation, or by simulation by a computer, and based on this, the voltage threshold value Vth can be appropriately set th1 For example, the relationship between the voltage value on the DC output side of the converter 11 and the output of the alarm signal in the motor drive device 1 can be obtained in advance by experiment or actual operation, or by simulation by a computer, and based on this, the voltage threshold value Vth can be appropriately set

[0032] The alarm signal output section 15 outputs an alarm signal at the time of an abnormality. The abnormality that causes the alarm signal to be output includes, for example, a failure of the motor drive device 1, a failure of a machine in which the motor drive device 1 is installed, an overload on the motor drive device 1, and a power failure of the AC power supply 2 that supplies power to the motor drive device 1. For example, the alarm signal output section 15 outputs an alarm signal when overcurrent, overvoltage, low voltage, or abnormal heat is detected by various detection sections (not shown) within the circuit of the motor drive device 1, or when a power failure of the AC power supply 2 is detected by a power failure detection section (not shown). The alarm signal output from the alarm signal output section 15 is sent to the switch control section 16. Alternatively, the alarm signal output section 15 can have a function of relaying an alarm signal output from a device provided outside the motor drive device 1 to the switch control section 16.

[0033] The switch control section 16 controls the upper arms U U , V U , and W U and the lower arms U L , V L , and W LSeparately configured switching elements are used for on / off control. One example of the control method for the switching elements by the switch control unit 16 is PWM control. The switch control unit 16 controls the power conversion operation of the inverter 12 by controlling the switching elements based on the motor 3's speed (speed feedback), motor 3's current (current feedback), a predetermined torque command, and the motor 3's operating program. The motor 3's speed, torque, or rotor position is controlled based on AC power supplied from the inverter 12, which has variable voltage and frequency. Furthermore, the structure of the switch control unit 16 described here is only one example; for example, the structure of the switch control unit 16 could also include terms such as a position command generation unit, a position control unit, a speed control unit, a current control unit, and a torque command generation unit.

[0034] Furthermore, in the first embodiment, when an alarm signal is output from the alarm signal output unit 15 and the DC link voltage determination unit 14 determines that the DC link voltage exceeds the voltage threshold V, th1 In the event of this, the switch control unit 16 stops the PWM-based switch control that is normally performed, and instead controls the lower arm U to switch on / off. L V L and W L All switching elements are turned on. Furthermore, if the lower arm U... L V L and W L When all the switching elements are turned on, it connects to the upper arm U. U V U and W U Regardless of the switching elements being turned on and off, the phases of the motor windings are short-circuited. Therefore, when an alarm signal is output from the alarm signal output unit 15 and the DC link voltage determination unit 14 determines that the DC link voltage exceeds the voltage threshold V, the circuit is short-circuited. th1 In this case, the upper arm U U V U and W U The switching element can be controlled to be on or off. When an alarm signal is output from the alarm signal output unit 15 and the motor 3 is stopped urgently, a large energy based on back electromotive force is generated. This energy based on back electromotive force (part or all) is absorbed by the motor windings that are in a phase-to-phase short-circuit state and the lower arm U. L V L and W L The energy consumed by the switching element in the ON state will not flow into the DC link capacitor 4. Therefore, a large increase in DC link voltage can be prevented, and there is no risk of damage to the DC link capacitor 4. Furthermore, due to the large energy flow through the lower arm U in the ON state, L V L and WL Therefore, there is a possibility that the switching element is broken. However, compared with the breakage (i.e., explosion) of the DC link capacitor 4, the breakage of the switching element has a less influence on the surroundings, and does not cause a harm to the body of the operator even if the operator is near the motor drive device 1.

[0035] The back electromotive force protection circuit 17 is provided between the AC output side of the inverter 12 and the motor 3. The back electromotive force protection circuit 17 has a rectifying section 31 and a short-circuit section 32.

[0036] The rectifying section 31 in the back electromotive force protection circuit 17 is a rectifier that rectifies AC power based on the back electromotive force of the motor 3 and outputs DC power. In the illustrated example, since the motor 3 is provided as a three-phase AC motor, the rectifying section 31 is configured by a three-phase full-bridge circuit, but in the case where the motor 3 is a single-phase motor, the rectifying section 31 is configured by a single-phase full-bridge circuit. As examples of the rectifying section 31, there are a diode rectifier, a 120-degree conduction type rectifier, a PWM switching control type rectifier, and the like.

[0037] The short-circuit section 32 in the back electromotive force protection circuit 17 has, for example, a switching mechanism that short-circuits or does not short-circuit the terminals on the DC output side of the rectifying section 31 depending on whether or not an alarm signal is output from the alarm signal output section 15. As examples of the switching mechanism, there are semiconductor elements such as IGBT, FET, thyristor, GTO, or transistor, or mechanical switches such as a relay, and the like. The switching operation by the short-circuit section 32 in the back electromotive force protection circuit 17 can be controlled by the switching control section 16, or a control section (not illustrated) different from the switching control section 16 can be provided. In the case where the alarm signal is output from the alarm signal output section 15, the short-circuit section 32 short-circuits the terminals on the DC output side of the rectifying section 31. In addition, in the case where the alarm signal is not output from the alarm signal output section 15 (i.e., in the case where it is in a normal state), the short-circuit section 32 does not short-circuit the terminals on the DC output side of the rectifying section 31, i.e., becomes a state where there is no connection between the terminals on the DC output side of the rectifying section 31. Therefore, the rectifying section 31 performs the operation of rectifying AC power and outputting DC power only in the case where the alarm signal is output from the alarm signal output section 15 and the terminals on the DC output side of the rectifying section 31 are short-circuited. In the case where the alarm signal is output from the alarm signal output section 15 and the motor 3 is urgently stopped, a large amount of energy (AC power) based on the back electromotive force is generated, and therefore the rectifying section 31 rectifies AC power based on the "back electromotive force of the motor 3" and outputs DC power.

[0038] As long as the back EMF protection circuit 17 operates normally, the energy of the back EMF generated during alarm output (i.e., when the motor 3 stops in an emergency) is entirely consumed by the motor windings, which are in a phase-to-phase short-circuit state, through the rectifier section 31 and short-circuit section 32 within the back EMF protection circuit 17, thereby stopping the motor 3 and preventing a significant increase in the DC link voltage. However, if the back EMF protection circuit 17 malfunctions, even though an alarm signal is output from the alarm signal output section 15, it is possible that the terminals on the DC output side of the rectifier section 31 are not short-circuited. When the back EMF protection circuit 17 malfunctions, the DC link voltage gradually increases. In the first embodiment, when it is determined that the DC link voltage exceeds the voltage threshold V... th1 In this case, the switch control unit 16 controls the lower arm U to... L V L and W L All the switching elements are turned on, so the energy based on the back electromotive force is supplied by the motor windings and the lower arm U, which are in a phase-to-phase short-circuit state. L V L and W L The switching elements consume energy. Therefore, it can prevent a large rise in DC link voltage and eliminates the risk of damage to DC link capacitor 4. Furthermore, even if energy based on back electromotive force flows through the lower arm U in the ON state... L V L and W L The impact of the broken switching element on the surrounding area is less severe than that of the broken (i.e., exploded) DC link capacitor 4.

[0039] In this way, when an alarm signal is output from the alarm signal output unit 15, the DC link voltage exceeds the voltage threshold V. th1 This indicates a malfunction in the back EMF protection circuit 17. When the back EMF protection circuit 17 malfunctions, the switch control unit 16 controls the lower arm U to... L V L and W L The operation of turning on all the switching elements. Therefore, in order to record and display the operation of turning on the lower arm U via the switch control unit 16. L V L and W L All the switching elements were turned on to notify the operator of the fault in the back EMF protection circuit 17, and a recording unit 18, a display unit 19, and an external device control unit 20 were provided in the motor drive unit 1.

[0040] Recording unit 18 records that an alarm signal was output from alarm signal output unit 15 and the DC link voltage determination unit 14 determined that the DC link voltage exceeded the voltage threshold V. th1 In the case of inverter 12, the lower arm UL , V L , and W L of all the switching elements are turned on. The recording section 18 is, for example, a hard disk drive (HDD), a solid state drive (SSD), an EEPROM (registered trademark), a DRAM, or an SRAM, which is attached to the motor drive device 1. It is also possible to display by printing on paper or the like using a printer after the fact based on the content recorded in the recording section 18.

[0041] The display section 19 displays the situation in which all the switching elements of the lower arm U th1 , V L , and W L in the inverter 12 are turned on in the case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold V L . As an example of the display section 19, there is a display, a portable terminal, and a touch panel, which are attached to the motor drive device 1.

[0042] The external device control section 20 controls so that an external device (not shown) records or displays the situation in which all the switching elements of the lower arm U th1 , V L , and W L in the inverter 12 are turned on in the case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold V L . In the external device, there are, for example, a hard disk drive (HDD), a solid state drive (SSD), an EEPROM (registered trademark), a DRAM, an SRAM, an attached display, a portable terminal, and a touch panel, which are provided outside the motor drive device 1.

[0043] In this way, the situation in which all the switching elements of the lower arm U L , V L , and W L are turned on is recorded, displayed, and controlled by the recording section 18, the display section 19, and the external device control section 20.the entire switching elements of the lower arm are turned on" and directly displays "the counter electromotive voltage protection circuit has failed." The operator can easily recognize that the counter electromotive voltage protection circuit 17 has failed based on the recorded content of the recording portion 18, the displayed content of the display portion 19, or the displayed content or recorded content of the external device. Therefore, the operator can immediately perform work such as repair or replacement of the counter electromotive voltage protection circuit 17, for example. In addition, the operator can analyze the content recorded in the recording portion 18 using an arithmetic processing device, for example, and thereby grasp the tendency of the abnormality occurring in the counter electromotive voltage protection circuit 17. The above-described display example of the display portion 19 is only one example, and the display portion 19 can display "the counter electromotive voltage protection circuit has failed" based on a character expression or a picture other than the display example. As an alternative example, instead of the display portion 19, a sound device such as a speaker, a buzzer, a bell, or the like that emits a sound can be implemented, in which case the sound device is preferably set to be silent during the normal operation of the counter electromotive voltage protection circuit 17. Alternatively, the display of the display portion 19 and the sound expression of the sound device can be appropriately combined to be implemented.

[0044] In addition, the motor drive device 1 does not necessarily have all of the recording portion 18, the display portion 19, and the external device control portion 20 at the same time, and can have them as appropriate.

[0045] Figure 2 is a diagram illustrating the operation of the counter electromotive voltage protection circuit in the motor drive device of the first to fifth embodiments of the present disclosure. Figure 2 Not only the first embodiment but also the second to fifth embodiments described later can be applied. Figure 2 In FIG. 6, the illustration of the alternating-current power supply 2, the converter 11, the DC link voltage detection portion 13, the DC link voltage determination portion 14, the recording portion 18, the display portion 19, and the external device control portion 20 is omitted.

[0046] The short-circuit portion 32 short-circuits or does not short-circuit the terminals on the direct-current output side of the rectifying portion 31 depending on whether the alarm signal is output from the alarm signal output portion 15. In the case where the alarm signal is output from the alarm signal output portion 15, the short-circuit portion 32 short-circuits the terminals on the direct-current output side of the rectifying portion 31. The current flowing through which phase diode among the diodes within the rectifying portion 31 changes depending on the magnitude of the phase voltage of each phase of the motor 3. For example Figure 2The flow of current at a certain instant is shown. The energy (AC power) of the counter electromotive force generated when the alarm signal is output from the alarm signal output section 15 and the motor 3 is urgently stopped is consumed by the motor winding in which the phases are in a short-circuit state via the rectifying section 31 and the short-circuit section 32 in the counter electromotive force protection circuit 17. Therefore, as long as the counter electromotive force protection circuit 17 does not malfunction, a large rise in the DC link voltage can be prevented, and there is no danger of the DC link capacitor 4 being broken.

[0047] Figure 3 is a diagram illustrating the flow of current when all of the switching elements of the lower arm in the inverter are turned on in the motor drive apparatuses of the first to fifth embodiments of the present disclosure. Figure 3 Not only can it be applied to the first embodiment, but also to the second to fifth embodiments described later (in the case where the electric resistance 41 is not electrically connected to the lower arm). In Figure 3 In, the illustration of the AC power supply 2, the converter 11, the DC link voltage detection section 13, the DC link voltage determination section 14, the recording section 18, the display section 19, and the external device control section 20 is omitted.

[0048] When all of the switching elements of the lower arm U L , V L , and W L in the inverter 12 are turned on, the phases of the motor winding of the motor 3 become in a short-circuit state regardless of the turning on and off of all of the switching elements of the upper arm U U , V U , and W U by the action of the switching elements in the on state and the diodes of the lower arm U L , V L , and W L . The energy of the counter electromotive force generated when the alarm signal is output from the alarm signal output section 15 and the motor 3 is urgently stopped is consumed by the motor winding in which the phases are in a short-circuit state and the switching elements of the lower arm U L , V L , and W L . Since all of the switching elements of the lower arm U L , V L , and W L are turned on, the energy based on the counter electromotive force does not flow into the DC link capacitor 4. Which of the switching elements and which of the diodes of the respective phases in which the current flows among the switching elements and the diodes of the respective phases of the lower arm U L , V L , and W L in the inverter 12 changes depending on the magnitude of the phase voltage of each phase of the motor 3. For example, Figure 3This illustrates the flow of current at a given moment, with the current flowing from the U-phase terminal of motor 3 through the lower arm U of the U-phase. L The switching element and the lower arm of phase W L The diode flows into the W-phase terminal of motor 3.

[0049] If a short circuit occurs in the short circuit section 32 within the back EMF protection circuit 17, and an alarm signal is output from the alarm signal output section 15, but the terminals on the DC output side of the rectifier section 31 are not short-circuited, then no short circuit occurs. Figure 2 As shown in the energy flow diagram, the DC link voltage gradually increases. In the first embodiment and the second to fifth embodiments described later, when it is determined that the DC link voltage exceeds the voltage threshold V... th1 In this case, the switch control unit 16 controls the lower arm U to... L V L and W L All the switching elements are turned on, so the energy based on the back electromotive force is supplied by the motor windings and the lower arm U, which are in a phase-to-phase short-circuit state. L V L and W L The switching elements consume power. Therefore, according to the first embodiment, even if the short circuit section 32 in the back EMF protection circuit 17 fails, a large increase in the DC link voltage can be prevented, and there is no risk of damage to the DC link capacitor 4.

[0050] Figure 4 This is a flowchart illustrating the operation flow of the motor drive device according to the first embodiment of this disclosure.

[0051] When the motor 3 is driven using AC power output from the inverter 12 by controlling the switching elements within the inverter 12 to be turned on and off via commands from the switch control unit 16, in step S101, the DC link voltage detection unit 13 detects the DC link voltage, which is the inter-terminal voltage of the DC link. The value of the DC link voltage detected by the DC link voltage detection unit 13 is sent to the DC link voltage determination unit 14.

[0052] In step S102, the switch control unit 16 determines whether an alarm signal has been output from the alarm signal output unit 15. For example, when overcurrent, overvoltage, undervoltage, or abnormal heating is detected by various detection units (not shown) in the circuit of the motor drive device 1, or when a power outage is detected by the power failure detection unit (not shown) that the AC power supply 2 has been de-energized, the alarm signal output unit 15 outputs an alarm signal. If it is determined in step S102 that an alarm signal has been output from the alarm signal output unit 15, the process proceeds to step S103; otherwise, it returns to step S101.

[0053] The processes of steps S101 and S102 are executed at a prescribed control cycle (for example, several milliseconds or so).

[0054] In step S103, the back electromotive force protection circuit 17 causes the short-circuit portion 32 to operate, to short-circuit the terminals on the DC output side of the rectifying portion 31. Here, as long as the back electromotive force protection circuit 17 is operating normally, the energy based on the back electromotive force generated at the time of the alarm output in step S102 is all consumed by the motor winding in the short-circuit state via the rectifying portion 31 and the short-circuit portion 32 within the back electromotive force protection circuit 17, and thus the motor 3 stops and the DC link voltage does not greatly increase. However, in the case where the back electromotive force protection circuit 17 has failed and the terminals on the DC output side of the rectifying portion 31 are not short-circuited despite the alarm signal being output from the alarm signal output portion 15, the DC link voltage gradually increases.

[0055] In step S104, the DC link voltage determination portion 14 determines whether or not the DC link voltage exceeds the voltage threshold value V th1 . The determination result of the DC link voltage determination portion 14 is sent to the switch control portion 16. In the case where it is determined in step S104 that the DC link voltage exceeds the voltage threshold value V th1 , step S105 is entered, and in the case where it is not determined that the DC link voltage exceeds the voltage threshold value V th1 , the process ends.

[0056] In step S105, the switch control portion 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. As a result, the inter-phase of the motor winding of the motor 3 becomes in the short-circuit state through the action of the switching elements of the lower arms U L , V L , and W L in the on state and the diodes. The energy based on the back electromotive force is consumed by the motor winding in the short-circuit state and the switching elements of the lower arms U L , V L , and W L in the on state, and thus the motor 3 stops and the DC link voltage does not increase. In addition, although not shown in FIG. 7, recording or display of "the lower arms U L , V L , and W L are turned on" is performed by the recording portion 18, the display portion 19, or the external device control portion 20. Figure 4 In step S105, the switch control portion 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. As a result, the inter-phase of the motor winding of the motor 3 becomes in the short-circuit state through the action of the switching elements of the lower arms U L , V L , and W L in the on state and the diodes. The energy based on the back electromotive force is consumed by the motor winding in the short-circuit state and the switching elements of the lower arms U L , V L , and W L in the on state, and thus the motor 3 stops and the DC link voltage does not increase. In addition, although not shown in FIG. 7, recording or display of "the lower arms U L , V L , and W L are turned on" is performed by the recording portion 18, the display portion 19, or the external device control portion 20. Figure 4 In step S105, the switch control portion 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. As a result, the inter-phase of the motor winding of the motor 3 becomes in the short-circuit state through the action of the switching elements of the lower arms U L , V L , and W L in the on state and the diodes. The energy based on the back electromotive force is consumed by the motor winding in the short-circuit state and the switching elements of the lower arms U L , V L , and W L in the on state, and thus the motor 3 stops and the DC link voltage does not increase. In addition, although not shown in FIG. 7, recording or display of "the lower arms U L , V L , and W L are turned on" is performed by the recording portion 18, the display portion 19, or the external device control portion 20.the processing of the operation of turning on all the switching elements. Thereafter, the processing is ended.

[0057] Next, the second embodiment will be described with reference to Figure 5 and Figure 6 The second embodiment is obtained by providing a switching element protection circuit in each of the lower arms in the motor drive device of the first embodiment.

[0058] Figure 5 is a diagram showing a motor drive device of the second embodiment of the present disclosure.

[0059] As shown in Figure 5 , the motor drive device 1 of the second embodiment of the present disclosure has, in addition to the circuit configuration elements in the motor drive device 1 of the first embodiment, a switching element protection circuit 21 connected in series with a group composed of a diode and a switching element in each of the lower arms U L , V L , and W L . The switching element protection circuit 21 has a resistor 41 and a switching switch 42 that selectively switches the electrical connection or electrical disconnection of the resistor 41 to the lower arms U L , V L , and W L . As the switching switch 42, there are IGBT, FET, thyristor, GTO, transistor, and the like, but other semiconductor elements can also be used. The switching operation of the switching switch 42 is controlled by the switching control section 16, for example, but a control section (not shown) different from the switching control section 16 can also be provided.

[0060] In a case where the motor drive device 1 is operating in a normal state and in a case where the alarm signal is output from the alarm signal output section 15 but the DC link voltage determination section 14 does not determine that the DC link voltage exceeds the voltage threshold V th1 , the switching switch 42 does not connect the resistor 41 to the lower arms. Therefore, the current does not flow through the resistor 41.

[0061] In a case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold V th1 , the switching switch 42 electrically connects the resistor 41 to the lower arms U L , V L , and W L . Therefore, the current flows through the resistor 41. Thereafter, the switching control section 16 controls to turn on all the switching elements of the lower arms U L , V L , and W L . At this time, the switching elements of the upper arms U U , VU and W U The switching element allows for either on / off control. Energy from the back electromotive force of the motor 3 flows through the switching switch 42, the resistor 41, and the lower arm U in the on state. L V L and W L The switching element. As a result, the energy based on the back electromotive force is not only supplied by the motor windings that are in a phase-to-phase short-circuit state, but also by the lower arm U that is in a closed state. L V L and W L The power consumed by the switching element is also consumed by resistor 41, thus preventing the lower arm U from being consumed. L V L and W L Damage to the switching element. Therefore, according to the second embodiment, damage to the DC link capacitor 4 and the lower arm U can be avoided. L V L and W L The switching element is damaged.

[0062] Regarding the second embodiment, the operation of circuit components other than the switching element protection circuit 21 and the switching control unit 16... Figure 1 The circuit components shown operate in the same way.

[0063] Figure 6 This is a flowchart illustrating the operation flow of the motor drive device according to the second embodiment of this disclosure.

[0064] Each process and reference in steps S201 to S203 Figure 4 The steps S101 to S103 described herein are the same.

[0065] In step S204, the DC link voltage determination unit 14 determines whether the DC link voltage exceeds the voltage threshold V. th1 The determination result of the DC link voltage determination unit 14 is sent to the switch control unit 16. In step S204, it is determined that the DC link voltage exceeds the voltage threshold V. th1 If the condition is not determined that the DC link voltage exceeds the voltage threshold V, proceed to step S205. th1 In this case, the process ends.

[0066] In step S205, the switching switch 42 connects the resistor 41 to the lower arm U. L V L and W L Electrical connection. Therefore, current flows through resistor 41.

[0067] In step S206, the switch control unit 16 controls the lower arm U to... L VL and W L are turned on. At this time, any one of the on control and the off control is performed on the switching elements of the lower arms U U , V U , and W U . Thus, the phase-to-phase of the motor winding of the motor 3 becomes a short-circuit state by the action of the switching elements of the lower arms U L , V L , and W L in the on state and the diodes. The energy based on the counter electromotive voltage is consumed by the motor winding in the short-circuit state, the resistor 41 in the switching element protection circuit 21, and the switching elements of the lower arms U L , V L , and W L in the on state, and thus the motor 3 stops and the DC link voltage does not rise. In addition, although not illustrated in Figure 6 , the process of recording or displaying the action of "turning on all the switching elements of the lower arms U L , V L , and W L " is executed by the recording section 18, the display section 19, or the external device control section 20. After that, the process ends.

[0068] Next, the third embodiment will be described with reference to Figure 7 and Figure 8 . The third embodiment is obtained by causing the switching switch in the switching element protection circuit to act in accordance with the temperature of the switching element of the lower arm in the motor drive device of the second embodiment.

[0069] Figure 7 is a diagram showing the motor drive device of the third embodiment of the present disclosure.

[0070] As shown in Figure 7 , the motor drive device 1 of the third embodiment of the present disclosure has, in addition to the circuit configuration elements in the motor drive device 1 of the second embodiment, a temperature detection section 22 and a temperature determination section 23.

[0071] A temperature sensor 51 is provided near each of the switching elements of the lower arms U L , V L , and W L . The temperature sensor 51 is preferably provided at a position where heat is most generated in each of the switching elements of the lower arms U L , V L , and W L . In addition, in Figure 7 , only the temperature sensor 51 provided to the lower arm U Ltemperature sensor provided near the switching element of the lower arm V L of phase W L of phase W L of phase W L of phase W L of phase W L of phase W L of phase W L of phase W

[0072] The temperature detection unit 22 detects the temperature of the switching element of the lower arm U L , V L , and W L via the temperature sensor 51. The detected temperature of the switching element is sent to the temperature determination unit 23. For example, in a case where the temperature sensor 51 is provided for all of the switching elements of the lower arms U L , V L , and W L , the temperature detection unit 22 detects the average of the temperatures of the three switching elements of the lower arms U L , V L , and W L , or the highest temperature among the temperatures of the three switching elements of the lower arms U L , V L , and W L as the "temperature of the switching element". For example, in a case where the temperature sensor 51 is provided for two of the switching elements of the lower arms U L , V L , and W L , the temperature detection unit 22 detects the average of the temperatures of the two switching elements, or the highest temperature among the temperatures of the two switching elements as the "temperature of the switching element". For example, in a case where the temperature sensor 51 is provided for one of the switching elements of the lower arms U L , V L , and W L , the temperature detection unit 22 detects the temperature of the one switching element as the "temperature of the switching element".

[0073] The temperature determination unit 23 determines whether the temperature of the switching element detected by the temperature detection unit 22 exceeds the temperature threshold T th . The temperature threshold T thThe temperature threshold value T is set to a value lower than the allowable temperature of the switching element, for example, several percent to several tens of percent. The numerical value shown here is an example, and the value can be other than this. As the allowable temperature of the switching element, for example, a value specified as one of the specification data in a specification table, a handling manual, or the like of the switching element can be used. Further, regarding the temperature threshold value T th , it can be stored in a rewritable storage section (not shown) and can be rewritten by an external device, and even after the temperature threshold value T th is temporarily set, it can be changed to an appropriate value as needed. The determination result of the temperature determination section 23 is sent to the switching control section 16.

[0074] In a case where the motor drive device 1 is operating in a normal state, in a case where the alarm signal is output from the alarm signal output section 15 but the DC link voltage determination section 14 does not determine that the DC link voltage exceeds the voltage threshold value V th1 , and in a case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold value V th1 , but the temperature determination section 23 does not determine that the temperature of the switching element exceeds the temperature threshold value T th , the switching switch 42 does not connect the resistance 41 to the lower arms U L , V L , and W L . Therefore, the current does not flow through the resistance 41.

[0075] In a case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold value V th1 , when it is determined by the temperature determination section 23 that the temperature of the switching element exceeds the temperature threshold value T th , the switching switch 42 connects the resistance 41 to the lower arms U L , V L , and W L . Therefore, the current flows through the resistance 41. After that, the switching control section 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. According to the third embodiment, in a case where the temperature of the switching element of the lower arms U L , V L , and W L exceeds the temperature threshold value T th which is set to a value lower than the allowable temperature, the resistance 41 is connected to the lower arms UL , V L , and W L are electrically connected. Thus, most of the energy based on the counter electromotive voltage is consumed by the motor winding in the short-circuit state between phases and the resistor 41, and thus abnormal heat generation of the switching elements of the lower arms U L , V L , and W L is avoided. As such, in the third embodiment as well, breakage of the DC link capacitor 4 and the switching elements of the lower arms U L , V L , and W L is avoided.

[0076] With regard to the third embodiment, the operations of the circuit configuration elements other than the temperature sensor 51, the temperature detection section 22, the temperature determination section 23, and the switching element protection circuit 21 are the same as those shown in the first embodiment. Figure 5

[0077] Figure 8 is a flowchart showing the operation flow of the motor drive device of the third embodiment of the present disclosure.

[0078] The processes of steps S301 to S303 are the same as the processes of steps S101 to S103 described with reference to the first embodiment. Figure 4

[0079] In step S304, the DC link voltage determination section 14 determines whether the DC link voltage exceeds the voltage threshold V th1 . The determination result of the DC link voltage determination section 14 is sent to the switching control section 16. In a case where it is determined in step S304 that the DC link voltage exceeds the voltage threshold V th1 , the process proceeds to step S305, and in a case where it is not determined that the DC link voltage exceeds the voltage threshold V th1 , the processing ends.

[0080] In step S305, the temperature detection section 22 detects the temperature of the switching elements of the lower arms U L , V L , and W L via the temperature sensor 51. The temperature of the switching elements detected by the temperature detection section 22 is sent to the temperature determination section 23.

[0081] In step S306, the temperature determination section 23 determines whether the temperature of the switching elements detected by the temperature detection section 22 exceeds the temperature threshold T th . The determination result of the temperature determination section 23 is sent to the switching control section 16. In a case where it is determined in step S306 that the temperature of the switching elements exceeds the temperature threshold T th ​​In the case where it is determined that the temperature of the switching element does not exceed the temperature threshold Tth in step S306, the process proceeds to step S307. In the case where it is determined that the temperature of the switching element exceeds the temperature threshold Tth in step S306, the process proceeds to step S308. th In the case where it is determined that the temperature of the switching element does not exceed the temperature threshold Tth in step S306, the process proceeds to step S307. In the case where it is determined that the temperature of the switching element exceeds the temperature threshold Tth in step S306, the process proceeds to step S308.

[0082] In step S307, the switching switch 42 electrically connects the resistor 41 to the lower arms U L , V L , and W L . Thus, the current flows through the resistor 41. The process then proceeds to step S308.

[0083] In step S308, the switching control section 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the turn-on control and the turn-off control can be performed. In addition, although not illustrated in Figure 8 , the process of recording or displaying that the action of "turning on all of the switching elements of the lower arms U L , V L , and W L " is performed by the recording section 18, the display section 19, or the external device control section 20. The process then ends.

[0084] Next, the fourth embodiment will be described with reference to Figure 9 and Figure 10 . The fourth embodiment is obtained by causing the switching switch within the switching element protection circuit to act in accordance with the current flowing through the switching elements of the lower arms in the motor drive device of the second embodiment.

[0085] Figure 9 is a diagram showing a motor drive device of the fourth embodiment of the present disclosure.

[0086] As shown in Figure 9 , the motor drive device 1 of the fourth embodiment of the present disclosure has, in addition to the circuit constituent elements in the motor drive device 1 of the second embodiment, a current detection section 24 and a current determination section 25.

[0087] The current detection section 24 detects the current flowing through the lower arms U L , V L , and W LThe current detection section 24 detects the current flowing through the switching element. In the case where the switching element is an IGBT and a transistor, the current detection section 24 detects the current flowing between the collector and the emitter, in the case where the switching element is an FET, the current detection section 24 detects the current flowing between the drain and the source, and in the case where the switching element is a thyristor and a GTO, the current detection section 24 detects the current flowing between the anode and the cathode. The value of the current flowing through the switching element detected by the current detection section 24 is sent to the current determination section 25.

[0088] In Figure 9 the drawing, only the mechanism for detecting the current flowing through the lower arm U L of the switching element of the U-phase is illustrated, and the illustration of the mechanism for detecting the current flowing through the lower arm V L of the switching element of the V-phase and the lower arm W L of the switching element of the W-phase is omitted. Further, as to the switching element which is the detection object of the current, either one or two of the switching elements of the lower arms U L , V L and W L may be provided, so as to reduce the cost. For example, in the case where the current flowing through all of the switching elements of the lower arms U L , V L and W L is detected by the current detection section 24, the current detection section 24 detects the average value of the currents flowing through the three switching elements of the lower arms U L , V L and W L or the maximum value among the values of the currents flowing through the three switching elements of the lower arms U L , V L and W L as the "current flowing through the switching element". For example, in the case where the current flowing through the switching elements of two of the lower arms U L , V L and W L is detected by the current detection section 24, the current detection section 24 detects the average value of the currents flowing through the two switching elements of the lower arms U L , V L and W L or the maximum value among the values of the currents flowing through the two switching elements of the lower arms U L , V L and W L as the "current flowing through the switching element". For example, in the case where the current flowing through the switching element of one of the lower arms U L , V L and W L is detected by the current detection section 24, the current detection section 24 detects the value of the current flowing through the one switching element as the "current flowing through the switching element".

[0089] The current determination section 25 determines whether the current of the switching element detected by the current detection section 24 exceeds the current threshold value I th The current threshold value I th may be set to a value lower than the maximum rated current of the switching element by, for example, several to several tens of percent. The numerical value example shown here is only one example, and the value can be other than this. As the maximum rated current of the switching element, for example, a value specified as one of the specification data in a specification table, a handling manual, or the like of the switching element can be used. Further, the current threshold value I th may be stored in a rewritable storage section (not shown) and can be rewritten by an external device, and even after the current threshold value I th is temporarily set, it can be changed to an appropriate value as needed. The determination result of the current determination section 25 is sent to the switching control section 16.

[0090] In the case where the motor drive device 1 is operating in the normal state, in the case where the alarm signal is output from the alarm signal output section 15 but the DC link voltage determination section 14 does not determine that the DC link voltage exceeds the voltage threshold value V th1 , and in the case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold value V th1 , but the current determination section 25 does not determine that the current flowing through the switching element exceeds the current threshold value I th , the changeover switch 42 does not connect the resistance 41 to the lower arms U L , V L , and W L . Therefore, the current does not flow through the resistance 41.

[0091] In the case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold value V th1 , when it is determined by the current determination section 25 that the detected current of the switching element exceeds the current threshold value I th , the changeover switch 42 connects the resistance 41 to the lower arms U L , V L , and W L . Therefore, the current flows through the resistance 41. After that, the switching control section 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. According to the fourth embodiment, in the case where the current flows through the lower arms UL , V L , and W L exceeds the current threshold I th , the resistor 41 is electrically connected to the lower arm U L , V L , and W L . Thereby, most of the energy based on the counter electromotive voltage is consumed by the resistor 41 and the motor winding in the short-circuit state between phases, and thus, it is possible to avoid excessive current from flowing through the switching elements of the lower arm U L , V L , and W L . As such, in the fourth embodiment as well, it is possible to avoid damage to the DC link capacitor 4 and the switching elements of the lower arm U L , V L , and W L .

[0092] With regard to the fourth embodiment, the operations of the circuit configuration elements other than the current detection section 24, the current determination section 25, and the switching element protection circuit 21 are the same as those described with regard to the first embodiment. Figure 5

[0093] Figure 10 is a flowchart showing the operation flow of the motor drive device of the fourth embodiment of the present disclosure.

[0094] The processes of steps S401 to S403 are the same as the processes of steps S101 to S103 described with reference to the first embodiment. Figure 4

[0095] In step S404, the DC link voltage determination section 14 determines whether the DC link voltage exceeds the voltage threshold V th1 . The determination result of the DC link voltage determination section 14 is transmitted to the switching control section 16. In the case where it is determined in step S404 that the DC link voltage exceeds the voltage threshold V th1 , the process proceeds to step S405, and in the case where it is not determined that the DC link voltage exceeds the voltage threshold V th1 , the process ends.

[0096] In step S405, the current detection section 24 detects the current flowing through the switching elements of the lower arm U L , V L , and W L . The value of the current flowing through the switching elements detected by the current detection section 24 is transmitted to the current determination section 25.

[0097] In step S406, the current determination section 25 determines whether the current of the switching elements detected by the current detection section 24 exceeds the current threshold I th ​​The determination result of the current determination section 25 is sent to the switch control section 16. In a case where it is determined in step S406 that the current of the switching element exceeds the current threshold I th , step S407 is entered, and in a case where it is not determined that the current of the switching element exceeds the current threshold I th , step S408 is entered.

[0098] In step S407, the changeover switch 42 electrically connects the resistor 41 to the lower arms U L , V L , and W L . Thus, the current flows through the resistor 41. Thereafter, step S408 is entered.

[0099] In step S408, the switch control section 16 controls to turn on all of the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. In addition, although not illustrated in Figure 10 , the processing of recording or displaying that the action of "turning on all of the switching elements of the lower arms U L , V L , and W L " is performed by the recording section 18, the display section 19, or the external device control section 20. Thereafter, the processing is ended.

[0100] Next, the fifth embodiment will be described with reference to Figure 11 and Figure 12 . The fifth embodiment is obtained by causing the changeover switch within the switching element protection circuit to act in accordance with the potential difference, i.e., the switching element voltage, of the conduction direction of the switching element of the lower arm in the motor drive device of the second embodiment.

[0101] Figure 11 is a diagram showing the motor drive device of the fifth embodiment of the present disclosure.

[0102] As shown in Figure 11 , the motor drive device 1 of the fifth embodiment of the present disclosure has, in addition to the circuit constituent elements in the motor drive device 1 of the second embodiment, a switching element voltage detection section 26 and a switching element voltage determination section 27.

[0103] The switching element voltage detection section 26 detects the switching element voltage of the lower arms U L , V L , and W LThe switch element voltage is the potential difference in the on direction of the switch element, i.e., the switch element voltage. The value of the switch element voltage detected by the switch element voltage detection section 26 is sent to the switch control section 16. In the case of an IGBT and a transistor as the switch element, the switch element voltage detection section 26 detects the switch element voltage flowing between the collector and the emitter, in the case of an FET as the switch element, the switch element voltage detection section 26 detects the switch element voltage flowing between the drain and the source, and in the case of a thyristor and a GTO as the switch element, the switch element voltage detection section 26 detects the switch element voltage flowing between the anode and the cathode.

[0104] In Figure 11 the drawing, for the sake of simplicity of the drawing, only the mechanism for detecting the switch element voltage of the lower arm U L is illustrated, and the illustration of the mechanism for detecting the switch element voltage of the lower arm V L and the lower arm W L of the V phase and the W phase is omitted. Further, as to the switch element which is the detection object of the switch element voltage, either one or two of the switch elements of the lower arms U L , V L , and W L may be provided, so as to reduce the cost. For example, in the case where the switch element voltages of all of the lower arms U L , V L , and W L are detected by the switch element voltage detection section 26, the switch element voltage detection section 26 detects the average value of the three switch element voltages of the lower arms U L , V L , and W L , or the maximum value among the values of the three switch element voltages of the lower arms U L , V L , and W L as the "switch element voltage". For example, in the case where the switch element voltages of two of the lower arms U L , V L , and W L are detected by the switch element voltage detection section 26, the switch element voltage detection section 26 detects the average value of the two switch element voltages of the lower arms U L , V L , and W L , or the maximum value among the values of the two switch element voltages of the lower arms U L , V L , and W L as the "switch element voltage". For example, in the case where the switch element voltage of one of the lower arms U L , V L , and W LIn a case where one of the switching element voltages is detected by the switching element voltage detection section 26, the switching element voltage detection section 26 detects the value of the one switching element voltage as the "switching element voltage".

[0105] The switching element voltage determination section 27 determines whether the switching element voltage detected by the switching element voltage detection section 26 exceeds the switching element voltage threshold value V th2 . The switching element voltage threshold value V th2 is set to a value lower than the allowable voltage in the conduction direction of the switching element, for example, several percent to several tens of percent. The numerical value example shown here is only one example, and the value can be other than this. As the allowable voltage of the switching element, for example, a value specified as one of the specification data in the specification table, handling manual, or the like of the switching element can be used. Furthermore, the switching element voltage threshold value V th2 may be stored in a rewritable storage section (not shown) and can be rewritten by an external device, and even after the switching element voltage threshold value V th2 is temporarily set, it can be changed to an appropriate value as needed. The determination result of the switching element voltage determination section 27 is sent to the switching control section 16.

[0106] In a case where the motor drive device 1 is operating in the normal state, in a case where the alarm signal is output from the alarm signal output section 15 but the DC link voltage determination section 14 does not determine that the DC link voltage exceeds the voltage threshold value V th1 , and in a case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold value V th1 , but the switching element voltage determination section 27 does not determine that the switching element voltage exceeds the switching element voltage threshold value V th2 , the changeover switch 42 does not connect the resistance 41 to the lower arms U L , V L , and W L . Therefore, current does not flow through the resistance 41.

[0107] In a case where the alarm signal is output from the alarm signal output section 15 and it is determined by the DC link voltage determination section 14 that the DC link voltage exceeds the voltage threshold value V th1 , when it is determined by the switching element voltage determination section 27 that the switching element voltage exceeds the switching element voltage threshold value V th2 , the changeover switch 42 connects the resistance 41 to the lower arms U L , V L , and W L . Therefore, current flows through the resistance 41. After that, the switching control section 16 controls to turn off the lower arms U L , V L , and W LAll of the switching elements are turned on. At this time, the switching elements of the upper arms U U , V U , and W U are subjected to either of the turn-on control and the turn-off control. According to the fifth embodiment, in a case where the switching element voltages of the lower arms U L , V L , and W L exceed the switching element voltage threshold value V th2 which is set to a value lower than the allowable voltage, the resistance 41 is electrically connected to the lower arms U L , V L , and W L . Thereby, most of the energy based on the counter electromotive voltage is consumed by the resistance 41 and the motor windings in the short-circuit state between phases, and thus overvoltage can be prevented from being applied to the switching elements of the lower arms U L , V L , and W L . As such, in the fifth embodiment, too, the DC link capacitor 4 and the switching elements of the lower arms U L , V L , and W L can be prevented from being broken.

[0108] As for the fifth embodiment, the operations of the circuit configuration elements other than the switching element voltage detection section 26, the switching element voltage determination section 27, and the switching element protection circuit 21 are the same as those described with reference to Figure 5 .

[0109] Figure 12 is a flowchart showing the operation flow of the motor drive device of the fifth embodiment of the present disclosure.

[0110] The processes of steps S501 to S503 are the same as those of steps S101 to S103 described with reference to Figure 4 .

[0111] In step S504, the DC link voltage determination section 14 determines whether the DC link voltage exceeds the voltage threshold value V th1 . The determination result of the DC link voltage determination section 14 is transmitted to the switching control section 16. In a case where it is determined in step S504 that the DC link voltage exceeds the voltage threshold value V th1 , the processing proceeds to step S505, and in a case where it is not determined that the DC link voltage exceeds the voltage threshold value V th1 , the processing is ended.

[0112] In step S505, the switching element voltage detection section 26 detects the switching element voltages of the lower arms U L , V L , and W Lthe potential difference in the conduction direction of the switching element, i.e., the switching element voltage. The value of the switching element voltage detected by the switching element voltage detection section 26 is sent to the switching control section 16.

[0113] In step S506, the switching element voltage determination section 27 determines whether the switching element voltage detected by the switching element voltage detection section 26 exceeds the switching element voltage threshold value V th2 . The determination result of the switching element voltage determination section 27 is sent to the switching control section 16. In the case where it is determined in step S506 that the switching element voltage exceeds the switching element voltage threshold value V th2 , the process proceeds to step S507, and in the case where it is not determined that the switching element voltage exceeds the switching element voltage threshold value V th2 , the process proceeds to step S508.

[0114] In step S507, the switching switch 42 electrically connects the resistance 41 to the lower arms U L , V L , and W L . Thus, current flows through the resistance 41. Thereafter, the process proceeds to step S508.

[0115] In step S508, the switching control section 16 controls to turn on all the switching elements of the lower arms U L , V L , and W L . At this time, with respect to the switching elements of the upper arms U U , V U , and W U , either of the on control and the off control can be performed. In addition, although not illustrated in Figure 12 , the process of recording or displaying that the operation of "turning on all the switching elements of the lower arms U L , V L , and W L " is performed by the recording section 18, the display section 19, or the external device control section 20. Thereafter, the process ends.

[0116] Further, the above-described third to fifth embodiments can be appropriately combined and implemented.

[0117] The DC link voltage determination section 14, the alarm signal output section 15, the switch control section 16, the recording section 18, the display section 19, the external device control section 20, the temperature detection section 22, the temperature determination section 23, the current determination section 25, and the switch element voltage determination section 27 can be constructed by, for example, a software program, or can be constructed by a combination of various electronic circuits and software programs, or can be constructed only by various electronic circuits. For example, in the case where these sections are constructed by a software program, the functions of the above-described sections can be realized by causing an arithmetic processing device such as a DSP, a FPGA, or the like to operate in accordance with the software program. Alternatively, the DC link voltage determination section 14, the alarm signal output section 15, the switch control section 16, the recording section 18, the display section 19, the external device control section 20, the temperature detection section 22, the temperature determination section 23, the current determination section 25, and the switch element voltage determination section 27 can be realized as a semiconductor integrated circuit in which a software program for realizing the functions of the sections is written. Alternatively, the DC link voltage determination section 14, the alarm signal output section 15, the switch control section 16, the recording section 18, the display section 19, the external device control section 20, the temperature detection section 22, the temperature determination section 23, the current determination section 25, and the switch element voltage determination section 27 can be realized as a recording medium in which a software program for realizing the functions of the sections is written. In addition, the DC link voltage determination section 14, the alarm signal output section 15, the switch control section 16, the recording section 18, the display section 19, the external device control section 20, the temperature detection section 22, the temperature determination section 23, the current determination section 25, and the switch element voltage determination section 27 can be provided in a numerical control device of a machine tool, or can be provided in a robot controller that controls a robot.

[0118] In addition, the DC link voltage detection section 13, the current detection section 24, and the switch element voltage detection section 26 can be constructed by a combination of an analog circuit and a digital circuit, or can be realized by an arithmetic processing device constructed in the form of a software program, or can be constructed only by an analog circuit. Further, as for the DC link voltage detection section 13, a component generally provided in the motor drive device 1 can be used.

[0119] In addition, the storage section that stores the voltage threshold value V th1 , the temperature threshold value T th , the current threshold value I th , and the switch element voltage threshold value V th2 may be constructed by, for example, a nonvolatile memory such as an EEPROM (registered trademark) that is electrically erasable and recordable, or a random access memory such as a DRAM, an SRAM, or the like that is capable of high-speed read and write.

[0120] According to one embodiment of the present disclosure, a large increase in a DC link voltage due to an abnormality can be reliably prevented in a motor drive device in which a converter and an inverter are connected via a DC link.

Claims

1. A motor drive device comprising: a converter that converts alternating-current power input from an alternating-current input side into direct-current power and outputs the direct-current power to a direct-current link that is a direct-current output side; an inverter that has switching elements connected in an antiparallel manner with diodes provided on an upper arm on a high potential side and a lower arm on a low potential side, respectively, and that converts direct-current power in the direct-current link into alternating-current power for driving a motor and outputs the alternating-current power by turning on and off the switching elements provided on the upper arm and the lower arm; a direct-current link voltage detection section that detects a direct-current link voltage that is an inter-terminal voltage of the direct-current link; a direct-current link voltage determination section that determines whether the direct-current link voltage exceeds a voltage threshold value; an alarm signal output section that outputs an alarm signal at an occurrence of any one of a failure of the motor drive device, a failure of a machine in which the motor drive device is provided, an overload on the motor drive device, and an abnormality of an alternating-current power source that supplies power to the motor drive device; a switching control section that turns on and off the switching elements; and a back electromotive force protection circuit that is provided between an alternating-current output side of the inverter and the motor, the back electromotive force protection circuit having a rectification section that outputs direct-current power after rectifying alternating-current power based on a back electromotive force of the motor and a short-circuit section that shorts inter-terminals of a direct-current output side of the rectification section in a case where the alarm signal is output from the alarm signal output section, wherein, in a case where the alarm signal is output from the alarm signal output section and the direct-current link voltage rises due to a failure of the back electromotive force protection circuit and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value, the switching control section controls to turn on all of the switching elements of the lower arm.

2. The motor drive device according to claim 1, further comprising a recording section that records that all of the switching elements of the lower arm are turned on in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value.

3. The motor drive device according to claim 1 or 2, further comprising a display section that displays that all of the switching elements of the lower arm are turned on in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value.

4. The motor drive device according to claim 1 or 2, further comprising an external device control section that controls an external device to record or display that all of the switching elements of the lower arm are turned on in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 5. The motor drive device according to claim 1 or 2, wherein a switching element protection circuit is further provided, the switching element protection circuit being connected in series with a group consisting of the diode and the switching element in the lower arm, the switching element protection circuit having a resistor and a switching switch that selectively switches electrical connection or electrical disconnection of the resistor to the lower arm.

6. The motor drive device according to claim 5, wherein in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value, the switching switch electrically connects the resistor to the lower arm.

7. The motor drive device according to claim 6, wherein in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value, after the switching switch electrically connects the resistor to the lower arm, the switching control section controls to turn on all of the switching elements of the lower arm.

8. The motor drive apparatus according to claim 5, wherein further comprising: a temperature detection section that detects a temperature of the switching element; and a temperature determination section that determines whether the temperature of the switching element exceeds a temperature threshold value, wherein in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value, when it is determined by the temperature determination section that the temperature of the switching element exceeds the temperature threshold value, the switching switch electrically connects the resistor to the lower arm.

9. The motor drive apparatus according to claim 5, wherein further comprising: a current detection section that detects a current flowing through the switching element; and a current determination section that determines whether the current detected by the current detection section exceeds a current threshold value, wherein in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value, when it is determined by the current determination section that the current exceeds the current threshold value, the switching switch electrically connects the resistor to the lower arm.

10. The motor drive apparatus according to claim 5, wherein further comprising: a switching element voltage detection section that detects a switching element voltage, the switching element voltage being a potential difference in an on direction of the switching element; and a switching element voltage determination section that determines whether the switching element voltage detected by the switching element voltage detection section exceeds a switching element voltage threshold value, wherein in a case where the alarm signal is output from the alarm signal output section and it is determined by the direct-current link voltage determination section that the direct-current link voltage exceeds the voltage threshold value, when it is determined by the switching element voltage determination section that the switching element voltage exceeds the switching element voltage threshold value, the switching switch electrically connects the resistor to the lower arm.

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