Motor drive unit

Abstract

The present invention provides a motor drive device, comprising: a main power conversion circuit, which converts power supplied from a power supply into AC power for driving a motor and outputs the AC power; a back electromotive force protection circuit, which is arranged between the AC output side of the main power conversion circuit and the motor, and has a rectifier, a short-circuit unit and an alarm signal output unit, the rectifier rectifies the AC power based on the back electromotive force of the motor and outputs DC power, the short-circuit unit short-circuits the terminals on the DC output side of the rectifier, and the alarm signal output unit outputs an alarm signal when an abnormality occurs; a monitoring unit, which monitors whether an alarm signal is output from the alarm signal output unit; and a protection action unit, which performs a protection action for preventing damage to the main power conversion circuit when the monitoring unit determines that an alarm signal is output from the alarm signal output unit.

Description

Technical Field

[0001] The invention relates to a motor driving device with a protection mechanism. Background Art

[0002] In a motor drive device that controls the drive of a motor in a machine tool, a forging machine, an injection molding machine, an industrial machine, or various robots, the motor is driven by AC power obtained by converting the power supplied from a power supply. The main power conversion circuit that generates the AC power for driving the motor has, for example, a converter and an inverter. More specifically, the AC power supplied from the AC power supply is converted into DC power by a converter, and the DC power is output to a DC link. The DC power in the DC link is then converted into AC power by an inverter, and the AC power is supplied to the motor as motor drive power. Here, the "DC link" refers to the circuit portion that electrically connects the DC output side of the converter to the DC input side of the inverter, and is sometimes also referred to as a "DC link portion", "DC link", "DC link portion", "DC bus" or "DC intermediate circuit". A DC link capacitor is provided in the DC link.

[0003] When an abnormality occurs in a motor drive device, a machine equipped with a motor drive device, or an AC power supply that supplies power to the motor drive device, the motor drive device causes the motor to stop urgently. At this time, energy based on the back electromotive force is generated in the motor. The energy generated in the motor is regenerated to the AC power supply or to a regenerative load (regenerative resistor) provided in the DC link. However, in the case of a large motor or a motor rotating at high speed, the energy based on the back electromotive force generated when the motor is stopped urgently is very large, and this energy cannot be regenerated to the AC power supply or the regenerative load. Therefore, some countermeasures are needed.

[0004] For example, as described in Japanese Patent Application Laid-Open No. 01-185186, a servo system protection device for abnormal current is known, characterized in that it comprises: a current instruction unit (102, 104) that issues a current instruction based on a position instruction and rotation angle position information sent from a rotation angle position detector of a servo motor; a current control unit (106) that receives the current instruction and generates a PWM signal; a power supply control unit (110, 112, 114, 116, 118, 120) that receives the PWM signal and controls the drive current supplied 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 rotation angle position information of the servo motor, determines whether the phase of the drive current corresponds to the rotation angle position, and cuts off the PWM signal if it does not correspond, wherein the current control unit receives the drive current information in addition to the current instruction and sends the PWM signal.

[0005] For example, as described in Japanese Patent Application Laid-Open No. 09-103088, there is known a motor drive circuit for supplying drive power to a motor, characterized in that the motor drive circuit is composed of a differential amplifier and a resistor, and operates to supply power of a specified voltage to the motor, a reference voltage is applied to a first input of the differential amplifier, the resistor is connected between the differential amplifier and the motor, and the motor side is connected to the second input of the differential amplifier, and an overcurrent detection circuit is provided in the motor drive circuit. The overcurrent detection circuit detects a voltage drop value generated by the resistor, and when the voltage drop value exceeds a specified voltage value, outputs a signal indicating that an overcurrent is flowing through the motor.

[0006] For example, in Japanese Patent Gazette No. 2004-103031, a method for detecting and diagnosing abnormalities in a servo control system is known, which is characterized in that when the power is turned on, the connection status of the sending side of the receiving circuit of multiple detectors is detected, and the model of the detector actually connected is automatically determined. When the detector type specified by the parameter is different from the detector actually connected, a parameter abnormality alarm is generated. Summary of the Invention

[0007] Problems to be solved by the invention

[0008] If the energy based on the back electromotive force generated when the motor is urgently stopped is large, the energy cannot be fully regenerated into the AC power supply or the regenerative load, and the DC link voltage rises significantly. Therefore, a back electromotive force protection circuit is sometimes provided to consume the energy based on the back electromotive force. However, even in the case where a back electromotive force protection circuit is provided, if the back electromotive force protection circuit fails, the energy based on the back electromotive force cannot be fully consumed, and the DC link voltage rises significantly. When the DC link voltage exceeds the withstand voltage of the DC link capacitor, the DC link capacitor is damaged, and as a result, the main power conversion circuit itself is also damaged, which is very dangerous. Therefore, a motor drive device is desired that can prevent damage to the DC link capacitor and the main power conversion circuit caused by abnormalities in the back electromotive force protection circuit.

[0009] According to one embodiment of the present disclosure, a motor drive device includes: a main power conversion circuit, which converts power supplied from a power supply into AC power for driving a motor and outputs the AC power; a back electromotive force protection circuit, which is arranged between the AC output side of the main power conversion circuit and the motor, and the back electromotive force protection circuit has a rectifier, a short-circuit unit and an alarm signal output unit, the rectifier rectifies the AC power based on the back electromotive force of the motor and outputs DC power, the short-circuit unit short-circuits the terminals on the DC output side of the rectifier, and the alarm signal output unit outputs an alarm signal when an abnormality occurs; a monitoring unit, which monitors whether an alarm signal is output from the alarm signal output unit; and a protection action unit, which performs a protection action for preventing damage to the main power conversion circuit when the monitoring unit determines that an alarm signal is output from the alarm signal output unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present invention will be more clearly understood with reference to the following drawings.

[0011] Figure 1 It is a diagram showing a motor drive device according to one embodiment of the present disclosure.

[0012] Figure 2 This is a circuit diagram showing an example of a main power conversion circuit including a converter and an inverter formed of a three-phase full-bridge circuit.

[0013] Figure 3 This is a diagram illustrating the operation of the back electromotive force protection circuit in the motor drive device according to one embodiment of the present disclosure.

[0014] Figure 4A 、 Figure 4B as well as Figure 4C This is a diagram illustrating an alarm signal output by an alarm signal output unit in a motor drive device according to an embodiment of the present disclosure.

[0015] Figure 5This is a flowchart showing the operation flow of the motor drive device according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0016] The following describes a motor drive device with a protective mechanism with reference to the accompanying drawings. The scales of these drawings have been appropriately changed to facilitate understanding. The embodiments shown in the drawings are examples for implementation and are not limited to the illustrated embodiments.

[0017] Figure 1 : is a diagram showing a motor drive device according to one embodiment of the present disclosure. Figure 2 This is a circuit diagram showing an example of a main power conversion circuit including a converter and an inverter formed of a three-phase full-bridge circuit.

[0018] As an example, the control of motor 3 by motor drive device 1 is shown. In this embodiment, the type of motor 3 is not particularly limited and may be, for example, an induction motor or a synchronous motor. Furthermore, the number of phases of motor 3 may be, for example, three-phase or single-phase. In the illustrated example, motor 3 is three-phase. Examples of machines equipped with motor 3 include machine tools, robots, forging presses, injection molding machines, industrial machinery, various electrical products, electric trains, automobiles, and aircraft.

[0019] like Figure 1 As shown, a motor drive device 1 according to an embodiment of the present disclosure includes a main power conversion circuit 11, a back electromotive force protection circuit 12, a monitoring unit 15, and a protection operation unit 13. Furthermore, the motor drive device 1 includes a motor control unit 14, a recording unit 16, a display unit 17, and an external device control unit 18.

[0020] The main power conversion circuit 11 converts the power supplied from the power source into AC power and outputs the AC power as power for driving the motor 3. Figure 1 In the illustrated example, the main power conversion circuit 11 includes a converter 21 , an inverter 22 , and a DC link capacitor 23 .

[0021] An AC power source 2 is connected to the AC input side of the converter 21. The number of phases of the AC power source 2 can be, for example, three-phase or single-phase. When enumerating an example of the AC power source 2, there are three-phase AC 400V power source, three-phase AC 200V power source, three-phase AC 600V power source, single-phase AC 100V power source, etc. Figure 1 and Figure 2 In the example shown, the AC power supply 2 is a three-phase AC power supply 2. Although an AC reactor, an AC line filter, an electromagnetic contactor, a circuit breaker, etc. may be provided between the converter 21 and the AC power supply 2, these are not shown here.

[0022] The converter 21 is a rectifier that converts AC power input from the AC input side into DC power and outputs the DC power to the DC link as the DC output side. Figure 1 and Figure 2 In the example shown, the AC power source 2 is a three-phase AC power source, so the converter 21 is composed of a three-phase full-bridge circuit. When single-phase AC power is supplied from the AC power source 2, the converter 21 functions as a single-phase bridge circuit. Examples of the converter 21 include a diode rectifier, a 120-degree conduction rectifier, and a PWM switching control rectifier. Figure 2 The illustrated example shows a diode rectifier comprised of a full-bridge diode circuit. Alternatively, if converter 21 is a 120-degree conduction mode rectifier or a PWM switching control mode rectifier, a full-bridge circuit is constructed of switching elements and diodes connected in antiparallel with the switching elements. Each switching element is controlled to be turned on and off in response to a drive command received from motor control unit 14, thereby performing power conversion in both AC and DC directions. Examples of switching elements used in converter 21 with a 120-degree conduction mode rectifier or a PWM switching control mode rectifier include IGBTs, FETs, thyristors, GTOs (Gate Turn-OFF thyristors), transistors, and the like, although other semiconductor elements may also be used.

[0023] A DC link capacitor 23 is provided in the DC link connecting the DC output side of converter 21 to the DC input side of inverter 22. DC link capacitor 23 has the function of storing DC power used by inverter 22 to generate AC power and suppressing ripple in the DC output of converter 21. Examples of DC link capacitor 23 include electrolytic capacitors and film capacitors. Furthermore, a regenerative load (regenerative resistor) may be provided in the DC link to consume regenerative energy from the motor.

[0024] The inverter 22 is connected to the converter 21 via a DC link, converts the DC power in the DC link into AC power for driving the motor, and outputs the AC power. Figure 1 and Figure 2 In the example shown, since the motor 3 is a three-phase AC motor, the inverter 22 is composed of a three-phase full-bridge circuit. If the motor 3 is a single-phase AC motor, the inverter 22 is composed of a single-phase full-bridge circuit. Figure 2As shown, in the inverter 22, which is composed of a three-phase full-bridge circuit, a switching element consisting of a diode connected in antiparallel is provided in the upper arm on the high-potential side and the lower arm on the low-potential side. Examples of switching elements include IGBTs, FETs, thyristors, GTOs, and transistors, but other semiconductor elements may also be used. Based on drive commands from the motor control unit 14, the inverter 22 switches the switching elements on and off, for example, using PWM control. This controls the DC power in the DC link to convert and output AC power for driving the motor. The speed, torque, and rotor position of the motor 3 are controlled based on the AC power supplied by the inverter 22. Furthermore, by appropriately performing PWM control on the switching elements by the motor control unit 14, the inverter 22 can regenerate the power generated by the motor 3 into the AC power source 2 or the DC link. A regenerative load (regenerative resistor) is provided in the DC link. When regenerating energy into the DC link, the regenerative load consumes the energy regenerated from the motor 3 via the inverter 22.

[0025] Alternatively, a DC power supply (not shown) such as a battery may be used as the power source for supplying electric power to the main power conversion circuit 11 instead of the AC power source 2 . In this case, the converter 21 can be omitted.

[0026] The motor control unit 14 controls the operation of the motor 3. The speed, torque, or rotor position of the motor 3 is controlled based on the AC power supplied from the main power conversion circuit 11. Consequently, the motor control unit 14 controls the motor 3 by controlling the power conversion operation of the main power conversion circuit 11. The motor control unit 14 controls the switching elements of the inverter 22 within the main power conversion circuit 11 to turn on and off. Examples of the control methods used by the motor control unit 14 for the switching elements of the inverter 22 include PWM control. The motor control unit 14 controls the power conversion operation of the inverter 22 by controlling the switching elements to turn on and off based on the rotational speed (speed feedback) of the motor 3, the current (current feedback) of the motor 3, a predetermined torque command, and the operation program of the motor 3. The speed, torque, or rotor position of the motor 3 is controlled based on, for example, the AC power supplied from the inverter 22, which has a variable voltage and a variable frequency. In addition, the structure of the motor control unit 14 described here is only an example. For example, the structure of the motor control unit 14 can also be specified by including terms such as position instruction generating unit, position control unit, speed control unit, current control unit, torque instruction generating unit, and switching instruction generating unit.

[0027] Furthermore, if converter 21 is a PWM switching control rectifier, motor control unit 14 also performs on-off control of the switching elements within converter 21 using the PWM control method. Furthermore, if converter 21 is a 120-degree conduction rectifier, motor control unit 14 turns on the switching element in the upper arm of the phase with the highest voltage of the three-phase AC power supply, and turns on the switching element in the lower arm of the phase with the lowest voltage of the three-phase AC power supply, each time the voltage of each phase of the three-phase AC power supply switches. This regenerates the DC power into the three-phase AC power supply.

[0028] The back electromotive force protection circuit 12 is provided between the AC output side of the inverter 22 in the main power conversion circuit 11 and the motor 3. The back electromotive force protection circuit 12 includes a rectifier 31, a short-circuit unit 32, an alarm signal output unit 33, and a temperature detector 34.

[0029] The rectifier 31 within the back-electromotive force protection circuit 12 is a rectifier that rectifies the AC power generated by the back-electromotive force of the motor 3 and outputs DC power. In the illustrated example, since the motor 3 is a three-phase AC motor, the rectifier 31 is configured as a three-phase full-bridge circuit. If the motor 3 is a single-phase AC motor, the rectifier 31 is configured as a single-phase full-bridge circuit. Examples of the rectifier 31 include a diode rectifier, a 120-degree conduction rectifier, and a PWM switching control rectifier.

[0030] The short-circuit section 32 in the back-electromotive force protection circuit 12 has a switching mechanism that short-circuits the terminals on the DC output side of the rectifier section 31 when it is necessary to consume the energy based on the back-electromotive force generated when the motor 3 is stopped, and does not short-circuit in other cases (i.e., when it is not necessary to consume the energy based on the back-electromotive force). For example, when the motor 3 is urgently stopped, the energy based on the back-electromotive force generated is very large. In order to consume this very large energy based on the back-electromotive force, the short-circuit section 32 in the back-electromotive force protection circuit 12 short-circuits the terminals on the DC output side of the rectifier section 31. Generally speaking, when the motor 3 is urgently stopped, an emergency stop signal is output from an external device. Therefore, the short-circuit section 32 in the back-electromotive force protection circuit 12 can be configured to short-circuit the terminals on the DC output side of the rectifier section 31 in conjunction with the output of the emergency stop signal from the external device.

[0031] The switching action performed by the short-circuit unit 32 in the back electromotive force protection circuit 12 can be controlled by, for example, the motor control unit 14, or a control unit (not shown) different from the motor control unit 14 can be provided. When the short-circuit unit 32 does not short-circuit the terminals on the DC output side of the rectifier 31, there is no connection between the terminals on the DC output side of the rectifier 31, so the rectifier 31 does not perform the action of rectifying the AC power and outputting the DC power. The rectifier 31 performs the action of rectifying the AC power and outputting the DC power only when the terminals on the DC output side of the rectifier 31 are short-circuited by the short-circuit unit 32. Examples of switching mechanisms include semiconductor elements such as IGBTs, FETs, thyristors, GTOs, or transistors, or mechanical switches such as relays.

[0032] Figure 3 1 is a diagram illustrating the operation of a back electromotive force protection circuit in a motor drive device according to an embodiment of the present disclosure. Figure 3 In the diagram, the recording unit 16, the display unit 17, and the external device control unit 18 are omitted. The phase of the diodes in the rectifier 31 through which the current flows changes depending on the magnitude of the phase voltage of each phase of the motor 3. For example, Figure 3 Shows the flow of current at a certain moment.

[0033] As long as the back-EMF protection circuit 12 operates normally, the energy from the back-EMF generated during an emergency stop of the motor 3 is completely dissipated by the motor windings, which are short-circuited between phases, via the rectifier 31 and short-circuiter 32 within the back-EMF protection circuit 12. This stops the motor 3 and prevents a significant increase in the DC-link voltage. However, if some abnormality occurs in the back-EMF protection circuit 12, the short-circuiter 32 does not short-circuit the DC output terminals of the rectifier 31, preventing the energy from the back-EMF from being dissipated. In this case, the DC-link voltage gradually rises. When it exceeds the withstand voltage of the DC-link capacitor 23, the DC-link capacitor 23 is damaged, which in turn damages the main power conversion circuit 11 itself. Therefore, in this embodiment, the protection action unit 13, described later, performs a protective action to prevent damage to the DC-link capacitor 23 and the main power conversion circuit 11.

[0034] The alarm signal output unit 33 in the counter electromotive force protection circuit 12 outputs an alarm signal when an abnormality occurs in the counter electromotive force protection circuit 12. Here, several examples of abnormalities in the counter electromotive force protection circuit 12 are listed.

[0035] The first abnormality may include, for example, a contact failure of the switch mechanism within the short-circuit section 32. When a contact failure occurs in the switch mechanism within the short-circuit section 32, the short-circuit section 32 is unable to short-circuit the terminals on the DC output side of the rectifier section 31 when it should. In this case, the alarm signal output unit 33 outputs an alarm signal. More specifically, a voltage application unit (not shown) and a current determination unit (not shown) are provided within the back-electromotive force protection circuit 12. The voltage application unit (not shown) applies a small voltage between the contact terminals of the switch mechanism within the short-circuit section 32 when it is assumed that the short-circuit section 32 has short-circuited the terminals on the DC output side of the rectifier section 31, and the current determination unit (not shown) determines whether current is flowing between the contacts. If the voltage application unit applies a small voltage between the contact terminals of the switch mechanism within the short-circuit section 32 when it is assumed that the short-circuit section 32 has short-circuited the terminals on the DC output side of the rectifier section 31, and the current determination unit determines that no current is flowing between the contacts, the alarm signal output unit 33 outputs an alarm signal.

[0036] A second abnormality, for example, is abnormal heating of components within the back-EMF protection circuit 12. When components within the back-EMF protection circuit 12 heat abnormally, the short-circuit unit 32 may be unable to short-circuit the terminals on the DC output side of the rectifier unit 31 when it should. In particular, when the switching mechanism within the short-circuit unit 32 is comprised of semiconductor switching elements, the operation of the semiconductor switching elements becomes unstable due to the abnormal heating. In this case, the alarm signal output unit 33 outputs an alarm signal. More specifically, a temperature detector 34 and a temperature determination unit (not shown) are provided within the back-EMF protection circuit 12. The temperature determination unit (not shown) determines whether the temperature detected by the temperature detector 34 exceeds a temperature threshold. If the temperature determination unit determines that the temperature detected by the temperature detector 34 exceeds the temperature threshold, the alarm signal output unit 33 outputs an alarm signal. For safety reasons, the temperature threshold can be set to a value, for example, several to ten percent lower than the permissible temperature of the components within the back-EMF protection circuit 12. The numerical values ​​shown here are merely examples; other values ​​are also possible. As the allowable temperature of the components within the back-electromotive force protection circuit 12, for example, a value specified as one of the specification data in a specification sheet or operating manual of the semiconductor switching element constituting the switching mechanism can be used. Furthermore, the temperature threshold value can be stored in a rewritable storage unit (not shown) and rewritable by an external device. Even after the temperature threshold value is temporarily set, it can be changed to an appropriate value as needed.

[0037] As a third abnormality, there is a failure of the control power supply (not shown) that supplies driving power to the short-circuit unit 32, for example. When the control power supply fails, the short-circuit unit 32 is sometimes unable to short-circuit when it should short-circuit the terminals on the DC output side of the rectifier unit 31. The alarm signal output unit 33 outputs an alarm signal in this case. In more detail, a voltage detection unit (not shown) and a voltage determination unit (not shown) are provided in the back electromotive force protection circuit 12. The voltage detection unit (not shown) detects the voltage output by the control power supply for supplying driving power to the short-circuit unit 32, and the voltage determination unit (not shown) determines whether a voltage is output from the control power supply. When the voltage determination unit determines that no voltage is output from the control power supply, the alarm signal output unit 33 outputs an alarm signal.

[0038] As described above, various types of abnormalities can occur in the counter electromotive force protection circuit 12 . Figure 4A 、 Figure 4B as well as Figure 4C This is a diagram illustrating an alarm signal output by the alarm signal output unit in the motor drive device according to one embodiment of the present disclosure. By assigning multiple types of abnormalities in the back electromotive force protection circuit 12 to each of the multiple types of alarm signals with different switching times and pulse widths between H (high) and L (low) per cycle, it is possible to determine the content of the abnormality generated in the back electromotive force protection circuit 12. For example, Figure 4A The alarm signal shown is assigned to the first abnormality (contact failure of the switch mechanism in the short-circuit section 32). Figure 4B The alarm signal shown is assigned to the second abnormality (abnormal heating of components in the back electromotive force protection circuit 12). Figure 4C The alarm signal shown is allocated to the third abnormality (failure of the control power supply for supplying driving power to the short-circuit unit 32). The waveform and allocation of the alarm signal shown here are merely examples, and other waveforms and allocations of the alarm signal may be used.

[0039] Return again Figure 1 The monitoring unit 15 monitors whether an alarm signal is output from the alarm signal output unit 33. The monitoring result of the monitoring unit 15 is transmitted to the protection operation unit 13. Furthermore, the monitoring unit 15 determines the nature of the abnormality occurring in the back-electromotive force protection circuit 12 based on the alarm signal output from the alarm signal output unit 33. The determination result of the monitoring unit 15 is transmitted to the recording unit 16, the display unit 17, and the external device control unit 18.

[0040] When the monitoring unit 15 determines that the alarm signal output unit 33 has output an alarm signal, the protection operation unit 13 executes a protection operation to prevent damage to the DC link capacitor 23 and the main power conversion circuit 11. Alternatively, the protection operation unit 13 may be provided within the motor control unit 14. Several embodiments of the protection operation performed by the protection operation unit 13 are listed below.

[0041] During the protection operation based on the first embodiment, if the monitoring unit 15 determines that an alarm signal has been output from the alarm signal output unit 33, the protection operation unit 13 controls the power conversion operation of the main power conversion circuit 11 so that the acceleration and deceleration of the motor 3 are reduced compared to the values ​​before the monitoring unit 15 made this determination. As described above, the power conversion operation of the inverter 22 within the main power conversion circuit 11 is controlled by the motor control unit 14. Therefore, the protection operation to prevent damage to the main power conversion circuit 11 is achieved by the protection operation unit 13 controlling the motor control unit 14. Through the protection operation based on the first embodiment, the acceleration and deceleration of the motor 3 are slowed compared to the values ​​before the monitoring unit 15 made this determination. For example, the acceleration and deceleration time constants used in the calculation processing for the acceleration and deceleration control of the motor 3 by the motor control unit 14 can be changed. The acceleration and deceleration time constants are defined as parameters in the program used by the motor drive device 1 to control the motor 3. If the monitoring unit 15 determines that an alarm signal has been output from the alarm signal output unit 33, the protection operation unit 13 changes the acceleration and deceleration time constants used in the calculation processing of the motor control unit 14 to values ​​greater than those set before the monitoring unit 15 made this determination. When the acceleration and deceleration control of the motor 3 is performed using the acceleration and deceleration time constants set to larger values, the acceleration and deceleration of the motor 3 are further reduced. As a result, the speed change of the motor 3 is slowed down, and the energy generated by the back electromotive force when the motor 3 is stopped is reduced. This suppresses the increase in the DC link voltage and prevents damage to the DC link capacitor 23 and the main power conversion circuit 11.

[0042] In the second embodiment of the protection operation, if the monitoring unit 15 determines that the alarm signal output unit 33 has output an alarm signal, the protection operation unit 13 executes control to stop excitation of the motor 3. By stopping excitation of the motor 3, the motor 3 stops through a so-called "free run stop," whereby the motor 3 rotates by inertia and then stops due to load and friction. This reduces the energy generated by the back electromotive force when stopping the motor 3, thereby suppressing the rise in the DC link voltage and preventing damage to the DC link capacitor 23 and the main power conversion circuit 11.

[0043] The purpose of the protective actions based on the first and second methods described above is to prevent damage to the DC link capacitor 23 and the main power conversion circuit 11. As a variation, the protective action unit 13 may cause an external device to execute a protective action to prevent damage to the motor 3 driven by the motor drive device 1, machinery equipped with the motor 3, and components connected to the motor 3.

[0044] The recording unit 16, display unit 17, and external device control unit 18 are provided to notify the operator of the details of an abnormality occurring in the back-EMF protection circuit 12. As described above, the monitoring unit 15 determines the details of the abnormality occurring in the back-EMF protection circuit 12 based on the alarm signal output from the alarm signal output unit 33. Therefore, the recording unit 16, display unit 17, and external device control unit 18 can record and display the details of the abnormality occurring in the back-EMF protection circuit 12 based on the determination result of the monitoring unit 15.

[0045] The recording unit 16 records the details of abnormalities occurring in the back-electromotive force protection circuit 12, as determined by the monitoring unit 15. The recording unit 16 may be, for example, a hard disk drive (HDD), a solid-state drive (SSD), an EEPROM (registered trademark), a DRAM, or an SRAM attached to the motor drive device 1. Furthermore, the contents recorded in the recording unit 16 may be subsequently printed out on paper or the like using a printer for display.

[0046] The display unit 17 displays the details of the abnormality occurring in the back-EMF protection circuit 12, as determined by the monitoring unit 15. Examples of the display unit 17 include a display, a portable terminal, and a touch panel attached to the motor drive device 1. For example, the display unit 17 can display information such as "a contact failure has occurred in the short-circuit portion of the back-EMF protection circuit," "abnormal heating of components within the back-EMF protection circuit," and "a failure in the control power supply within the back-EMF protection circuit." The above display example of the display unit 17 is merely an example; the display unit 17 may also display the details of the abnormality occurring in the back-EMF protection circuit 12 using text or images other than those shown. Alternatively, the display unit 17 may be replaced with an audio device that emits sound, such as voice, a speaker, a buzzer, or a ringtone. In this case, the audio device is preferably muted during normal operation of the back-EMF protection circuit 12. Alternatively, the display unit 17 may be displayed by appropriately combining the audio output of the audio device with the display of the display unit 17.

[0047] The external device control unit 18 controls an external device (not shown) to record or display the details of an abnormality generated in the back electromotive force protection circuit 12, which has been identified by the monitoring unit 15. Examples of the external device include 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.

[0048] The operator can easily identify the occurrence of an abnormality in the back-EMF protection circuit 12 and the nature of the abnormality based on the recorded contents of the recording unit 16, the displayed contents of the display unit 17, or the displayed contents or recorded contents of an external device. Therefore, the operator can immediately perform operations such as repairing or replacing the back-EMF protection circuit 12. Furthermore, the operator can analyze the contents recorded in the recording unit 16 using, for example, a processing device to understand the tendency of abnormalities occurring in the back-EMF protection circuit 12.

[0049] In addition, the motor drive device 1 does not necessarily need to include all of the recording unit 16 , the display unit 17 , and the external device control unit 18 , and may include them appropriately as needed.

[0050] Figure 5 This is a flowchart showing the operation flow of the motor drive device according to one embodiment of the present disclosure.

[0051] In step S101 , in the motor drive device 1 of the present embodiment, the motor control unit 14 controls the power conversion operation of the inverter 22 to drive the motor 3 .

[0052] In step S102, the motor control unit 14 determines whether energy based on the back electromotive force generated when the motor 3 is stopped is generated. If it is determined in step S102 that energy based on the back electromotive force is generated, the process proceeds to step S103. If it is not determined that energy based on the back electromotive force is generated, the process returns to step S101. In addition, as an alternative to step S102, when the terminals on the DC output side of the rectifier 31 are short-circuited in conjunction with the emergency stop signal output from the external device by short-circuiting the short-circuit unit 32, the motor control unit 14 determines whether an emergency stop signal is output from the external device. In this alternative, if it is determined in step S102 that an emergency stop signal is output from the external device, the process proceeds to step S103. If it is not determined that an emergency stop signal is output from the external device, the process returns to step S101.

[0053] In step S103, the back-EMF protection circuit 12 activates the short-circuit unit 32 to short-circuit the terminals on the DC output side of the rectifier unit 31. As long as the back-EMF protection circuit 12 operates normally, all the energy generated by the back EMF is dissipated by the short-circuited motor windings through the rectifier unit 31 and short-circuit unit 32 within the back-EMF protection circuit 12, stopping the motor 3 and preventing a significant increase in the DC link voltage. However, if an abnormality occurs in the back-EMF protection circuit 12, the terminals on the DC output side of the rectifier unit 31 are not short-circuited, and the DC link voltage gradually increases. If an abnormality occurs in the back-EMF protection circuit 12, the alarm signal output unit 33 outputs an alarm signal.

[0054] In step S104, the monitoring unit 15 monitors whether an alarm signal has been output from the alarm signal output unit 33. If it is determined in step S104 that an alarm signal has been output from the alarm signal output unit 33, the process proceeds to step S105. On the other hand, if it is determined in step S104 that an alarm signal has not been output from the alarm signal output unit 33, the energy generated by the back electromotive force has been completely dissipated by the motor windings, which are in a short-circuited state between phases, via the rectifier unit 31 and short-circuit unit 32 within the back electromotive force protection circuit 12, which are operating normally. This stops the motor 3, and the DC link voltage does not rise significantly, thus terminating the process.

[0055] In step S105, the protection operation unit 13 executes a protection operation to prevent damage to the main power conversion circuit 11. By executing the protection operation, the energy based on the back electromotive force generated when the motor 3 is stopped is reduced, thereby suppressing the rise of the DC link voltage and preventing damage to the DC link capacitor 23 and the main power conversion circuit 11. Figure 5 Although not shown in the figure, the recording unit 16, the display unit 17, or the external device control unit 18 performs a process of recording or displaying the details of the abnormality generated in the counter electromotive force protection circuit 12. The process is then terminated.

[0056] The aforementioned protection operation unit 13, motor control unit 14, monitoring unit 15, recording unit 16, display unit 17, external device control unit 18, and alarm signal output unit 33 can be implemented, for example, as a software program, or as a combination of various electronic circuits and software programs, or even solely as various electronic circuits. For example, if these components are implemented as software programs, the functions of each component can be realized by having a processing device such as a DSP or FPGA operate according to the software program. Alternatively, the protection operation unit 13, motor control unit 14, monitoring unit 15, recording unit 16, display unit 17, external device control unit 18, and alarm signal output unit 33 be implemented as a semiconductor integrated circuit on which a software program for realizing the functions of each component is written. Alternatively, the protection operation unit 13, motor control unit 14, monitoring unit 15, recording unit 16, display unit 17, external device control unit 18, and alarm signal output unit 33 can be implemented as a recording medium on which a software program for realizing the functions of each component is written. In addition, the protection action unit 13, motor control unit 14, monitoring unit 15, recording unit 16, display unit 17, external device control unit 18 and alarm signal output unit 33 can be set in the numerical control device of the machine tool or in the robot controller that controls the robot.

[0057] The temperature detection unit 34 may be configured by a combination of an analog circuit and a digital circuit, or may be configured by only an analog circuit.

[0058] The storage unit storing the temperature threshold value may be formed of, for example, an electrically erasable and recordable nonvolatile memory such as EEPROM (registered trademark), or a high-speed readable and writable random access memory such as DRAM or SRAM.

[0059] According to one embodiment of the present disclosure, it is possible to realize a motor drive device capable of preventing damage to a DC link capacitor and a main power conversion circuit caused by abnormality in a back electromotive force protection circuit.

Claims

1. A motor drive device comprising: a main power conversion circuit that converts the electric power supplied from the power source into AC power for driving the motor and outputs the AC power; a back-electromotive force protection circuit provided between the AC output side of the main power conversion circuit and the motor, the back-electromotive force protection circuit comprising a rectifier unit, a short-circuiter unit, and an alarm signal output unit. The rectifier unit rectifies AC power based on the back-electromotive force of the motor and outputs DC power. The short-circuiter unit short-circuits terminals on the DC output side of the rectifier unit. The alarm signal output unit outputs an alarm signal when an abnormality occurs. a monitoring unit that monitors whether the alarm signal is output from the alarm signal output unit; as well as a protection operation unit that performs a protection operation for preventing damage to the main power conversion circuit when the monitoring unit determines that the alarm signal is output from the alarm signal output unit; The alarm signal output unit outputs one of an alarm signal indicating a first abnormality, which is a contact failure of a switch mechanism in the short-circuit portion, an alarm signal indicating a second abnormality, which is abnormal heating of a component in the back electromotive force protection circuit, and an alarm signal indicating a third abnormality, which is a failure of a control power supply supplying drive power to the short-circuit portion. The monitoring unit determines whether the abnormality occurring in the counter electromotive force protection circuit is the first abnormality, the second abnormality, or the third abnormality based on the alarm signal output from the alarm signal output unit.

2. The motor drive device according to claim 1, wherein: A recording unit is further provided for recording the details of the abnormality identified by the monitoring unit.

3. The motor drive device according to claim 2, wherein: A display unit is further provided for displaying the details of the abnormality identified by the monitoring unit.

4. The motor drive device according to claim 2, wherein: The device further includes an external device control unit configured to control an external device to record or display the details of the abnormality identified by the monitoring unit.

5. The motor drive device according to claim 3, wherein: The device further includes an external device control unit configured to control an external device to record or display the details of the abnormality identified by the monitoring unit.

6. The motor drive device according to any one of claims 1 to 5, wherein: When the monitoring unit determines that the alarm signal is output from the alarm signal output unit, the protection operation unit controls the power conversion operation of the main power conversion circuit so that the acceleration and deceleration of the motor become smaller than the values ​​before the monitoring unit makes the determination.

7. The motor drive device according to any one of claims 1 to 5, wherein: The protection operation unit executes control for stopping excitation of the motor when the monitoring unit determines that the alarm signal is output from the alarm signal output unit.

8. The motor drive device according to any one of claims 1 to 5, wherein: The main power conversion circuit has: a converter that converts AC power supplied from the AC input side into DC power and outputs the DC power to the DC link serving as the DC output side; a DC link capacitor, which is arranged in the DC link; as well as An inverter converts the DC power in the DC link into AC power for driving the motor and outputs the AC power.

9. The motor drive device according to claim 6, wherein: The main power conversion circuit has: a converter that converts AC power supplied from the AC input side into DC power and outputs the DC power to the DC link serving as the DC output side; a DC link capacitor, which is arranged in the DC link; as well as An inverter converts the DC power in the DC link into AC power for driving the motor and outputs the AC power.

10. The motor drive device according to claim 7, wherein: The main power conversion circuit has: a converter that converts AC power supplied from the AC input side into DC power and outputs the DC power to the DC link serving as the DC output side; a DC link capacitor, which is arranged in the DC link; as well as An inverter converts the DC power in the DC link into AC power for driving the motor and outputs the AC power.

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