Motor drive

Abstract

The present invention provides a motor drive device, comprising: a rectifier, which converts AC power on the AC input side into DC power and outputs it to a DC link; an inverter, which converts DC power in the DC link into AC power for motor driving; a DC link voltage detection unit, which detects the DC link voltage; an input current detection unit, which detects an input current input to the rectifier; a DC link voltage comparison unit, which compares the DC link voltage with a first voltage threshold and a second voltage threshold, respectively; a current comparison unit, which compares the input current with the current threshold; and an abnormality detection unit, which, when the DC link voltage is lower than the first voltage threshold or the DC link voltage is higher than the second voltage threshold, determines that a first abnormality has occurred when the input current is lower than the current threshold, and determines that a second abnormality has occurred when the input current is higher than the current threshold.

Description

Technical Field

[0001] The present invention relates to a motor driving device for determining the cause of direct current (DC) link voltage variation. 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, a rectifier is used to convert the AC power supplied from an AC power source into DC power and then output it to a DC link, and an inverter is used to convert the DC power in the DC link into AC power, and the AC power is supplied to the motor as motor drive power. A "DC link" refers to a circuit portion that electrically connects the DC output side of a rectifier to the DC input side of an 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] Generally, the capacity of the DC link capacitor is smaller than the capacity of the power supply. Therefore, for example, when the motor is accelerated when the AC power from the AC power supply is not supplied to the rectifier in the motor drive device due to some reason, the acceleration energy of the motor is supplied only from the DC link capacitor, and the DC link voltage drops instantaneously. In addition, for example, when the power regeneration to the AC power supply via the rectifier is insufficient due to some reason when the motor is decelerating, the DC link voltage rises instantaneously.

[0004] In a motor drive device, when the voltage between the terminals of the DC link, i.e., the DC link voltage, drops or rises significantly due to some reason, the motor cannot continue to operate normally. As a result, not only the motor drive device, but also the motor driven by the motor drive device, various devices connected to the motor, and various systems having the motor drive device may also be damaged or deformed. Therefore, when the DC link voltage drops or rises significantly, an alarm signal is output from the control device in the motor drive device. Based on the alarm signal, an emergency stop and protection action of the motor drive device are performed to avoid the above-mentioned fault or minimize the above-mentioned fault.

[0005] For example, as described in Japanese Patent Gazette No. 2018-121408, a motor drive device is known, which has an abnormality detection function for a power input part between the device and a power supply, and the motor drive device includes: a converter, which inputs AC power from the power supply via the power input part and converts the AC power into DC power; an inverter, which converts the DC power from the converter into AC power; a DC link capacitor, which is arranged in a DC link between the converter and the inverter; a voltage detection unit, which detects the voltage of the DC link capacitor; and an abnormality detection unit, which calculates a voltage change of the DC link capacitor within a specified time based on the voltage value detected by the voltage detection unit, and performs abnormality detection of the power input part based on the calculated voltage change.

[0006] For example, as described in Japanese Patent Application Laid-Open No. 2015-216018, a motor drive device is known, characterized in that it includes: an AC / DC converter that converts an AC voltage supplied from an AC power source into a DC voltage; an electromagnetic contactor that performs switching for connecting or disconnecting the AC power source and the AC / DC converter; a DC link that smoothes the DC voltage output from the AC / DC converter; a DC / AC converter that converts the DC voltage smoothed by the DC link into an AC voltage for motor driving; a DC link voltage detector that measures a voltage between terminals of the DC link; and a control unit that sends a signal to the DC link to drive the motor. The control unit controls the AC / DC conversion unit by sending an instruction to connect or disconnect the electromagnetic contactor, wherein the control unit has: a time measuring unit that measures the time elapsed from the switching by the electromagnetic contactor; and a welding determination unit that determines that the electromagnetic contactor has been welded when the difference between the terminal voltage of the DC link unit after the AC power supply is connected to the AC / DC conversion unit to charge the DC link unit and the terminal voltage of the DC link unit after a predetermined time has passed since the control unit sent an instruction to disconnect the AC power supply from the AC / DC conversion unit after charging the DC link unit is less than a predetermined voltage value.

[0007] For example, as described in Japanese Patent Publication No. 2018-102082, a motor drive device is known, comprising: at least one inverter, each inverter converting the DC power from a converter for converting AC power into DC power into AC power; a DC link capacitor, which is provided for each of the inverters and is provided in a DC link between the converter and the inverter; a first current detection unit, which detects a current flowing between the converter in the DC link and the DC link capacitor; a second current detection unit, which detects a current flowing between the DC link capacitor in the DC link and the inverter; and a voltage detection unit. a portion for detecting the voltage of the DC link capacitor; and a capacity reduction detecting portion for determining a change in charge of the DC link capacitor within a predetermined time based on an integrated value obtained by integrating a difference between a current value detected by the first current detecting portion and a current value detected by the second current detecting portion over a predetermined time, determining a change in voltage of the DC link capacitor within the predetermined time based on a voltage value detected by the voltage detecting portion, determining a capacitance value of the DC link capacitor based on the determined change in charge and change in voltage, and detecting a capacity reduction of the DC link capacitor based on the determined capacitance value.

[0008] For example, paragraph

[0003] of Japanese Patent Application Laid-Open No. 2012-151959 states that “In such a power conversion device, an abnormality detection unit for detecting an abnormality in power supply voltage (eg, an instantaneous voltage drop) is provided in order to protect an inverter unit, etc.”

[0009] For example, as described in Japanese Patent Application Laid-Open No. 2019-138656, a motor drive device is known, comprising: a converter that converts AC power input from an AC power supply into DC power and outputs the converted power; a DC link unit that is connected in parallel to the DC output side of the converter and has a plurality of capacitors connected in series with each other; an inverter that is connected in parallel to the DC link unit and converts the DC power in the DC link unit into AC power for driving a motor and outputs the converted power; and a short-circuit determination unit that compares the value of the DC current flowing between the DC link unit and the inverter with a predetermined first threshold value, and compares the value of the input current flowing from the AC power supply via the converter to the DC link unit with a predetermined second threshold value, and when the result of the comparison is that the value of the DC current flowing between the DC link unit and the inverter is lower than the first threshold value and the value of the input current flowing from the AC power supply via the converter to the DC link unit exceeds the second threshold value, the short-circuit determination unit determines that at least one of the plurality of capacitors in the DC link unit is short-circuited.

[0010] For example, as described in Japanese Patent Gazette No. 2011-217518, a motor drive device is known, comprising: an AC / DC conversion unit that converts three-phase AC from a three-phase AC power supply into DC; and a DC / AC conversion unit that converts the DC output from the AC / DC conversion unit into three-phase AC and supplies it to a motor, the motor drive device also comprising: a total current detection unit that detects the total of currents flowing from the three-phase AC power supply through the AC / DC conversion unit to the DC / AC conversion unit; an overcurrent detection unit that detects an overcurrent in the output current of the DC / AC conversion unit; and a determination unit, wherein when the overcurrent detection unit detects an overcurrent, if the determination unit can determine that the sum of the currents detected by the total current detection unit is not zero, it is determined that a ground short circuit has occurred, and if it can be determined that the sum of the currents detected by the total current detection unit is zero, it is determined that an interphase short circuit has occurred. Summary of the invention

[0011] The reasons for a significant drop or increase in the DC link voltage include, for example, a long-term power outage of the AC power supply, an instantaneous power outage, insufficient capacity of the power supply equipment, overload, failure of the motor drive device itself, and disconnection of the circuit breaker and electromagnetic contactor. Based on the output of the alarm signal and the measurement results of the DC link voltage, the phenomenon of a significant drop or increase in the DC link voltage itself can be detected, but the work of determining its cause takes effort and time. In the case where the DC link voltage has dropped or increased significantly, generally speaking, the operator first starts to investigate the cause of the significant drop or increase in the DC link voltage from the motor drive device. However, in the case where the cause of the significant drop or increase in the DC link voltage is not the motor drive device, it takes time until the real cause is found. During the period when the operator is investigating the cause, the machine driven by the motor drive device stops running, resulting in a decrease in the operating rate of the machine.

[0012] In addition, the operator should take different measures depending on the cause of the DC link voltage drop or increase. For example, when the cause of the DC link voltage drop or increase is not a failure of the motor drive device itself, the operator does not need to replace the motor drive device itself or replace or repair the components in the motor drive device. However, if the cause of the DC link voltage drop or increase cannot be accurately determined, sometimes the operator mistakenly identifies that the motor drive device has a failure even though the motor drive device is normal. As a result, it is not economical to unnecessarily replace the normal motor drive device itself or unnecessarily replace or repair the components in the motor drive device.

[0013] Therefore, a technology is desired that can easily and accurately determine the cause of a significant drop or rise in a DC link voltage in a motor drive device in which a rectifier and an inverter are connected via a DC link.

[0014] According to one embodiment of the present disclosure, a motor drive device includes: a rectifier that converts AC power input from an AC input side into DC power and outputs the converted power to a DC link as a DC output side; an inverter that converts the DC power in the DC link into AC power for motor driving and outputs the converted power; a DC link voltage detection unit that detects a DC link voltage that is a voltage between terminals of the DC link; an input current detection unit that detects an input current input from the AC input side of the rectifier; a DC link voltage comparison unit that compares the DC link voltage with a first voltage threshold and a second voltage threshold, respectively, the second voltage threshold being set to a value higher than the first voltage threshold; a current comparison unit that compares the input current with the current threshold; and an abnormality detection unit that, when the DC link voltage comparison unit determines that the DC link voltage is lower than the first voltage threshold or determines that the DC link voltage is higher than the second voltage threshold, determines that a first abnormality has occurred when the current comparison unit determines that the input current is lower than the current threshold, and determines that a second abnormality has occurred when the current comparison unit determines that the input current is greater than the current threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will be more clearly understood by referring to the following drawings.

[0016] Figure 1 is a diagram illustrating a motor driving device according to an embodiment of the present disclosure.

[0017] Figure 2 1 is a flowchart showing the operation flow of the motor drive device according to one embodiment of the present disclosure.

[0018] Figure 3 FIG. 1 is a diagram showing a motor drive device according to a modified example of one embodiment of the present disclosure.

[0019] Figure 4 1 is a flowchart showing the operation flow of the motor drive device according to a modified example of one embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] The motor drive device for determining the cause of DC link voltage fluctuation is described below with reference to the accompanying drawings. For ease of understanding, the scales in these drawings are appropriately changed. The embodiments shown in the drawings are examples for implementation and are not limited to the illustrated embodiments.

[0021] Figure 1 is a diagram illustrating a motor driving device according to an embodiment of the present disclosure.

[0022] As an example, a case where the motor 3 is controlled by a motor drive device 1 connected to an AC power supply 2 is shown. In the present embodiment, the type of the motor 3 is not particularly limited, and for example, it may be an induction motor or a synchronous motor. In addition, the number of phases of the AC power supply 2 and the motor 3 is not particularly limited to the present embodiment, and for example, it may be three-phase or single-phase. In the illustrated example, the AC power supply 2 and the motor 3 are respectively set to three-phase. If an example of the AC power supply 2 is cited, there are three-phase AC 400V power supply, three-phase AC 200V power supply, three-phase AC 600V power supply, single-phase AC 100V power supply, and the like. Machines in which the motor 3 is provided include, for example, machine tools, robots, forging machines, injection molding machines, industrial machinery, various electrical products, trams, automobiles, airplanes, and the like.

[0023] like Figure 1 As shown, the motor drive device 1 according to one embodiment of the present disclosure includes: a rectifier 11, an inverter 12, a DC link voltage detection unit 13, an input current detection unit 14, a DC link voltage comparison unit 15, a current comparison unit 16, and an abnormality detection unit 17. In addition, the motor drive device 1 includes a display unit 23, an electromagnetic contactor 18 as a first opening and closing unit, and a circuit breaker 19 as a second opening and closing unit.

[0024] The rectifier 11 converts the AC power input from the AC input side into DC power and outputs it to the DC link as the DC output side. The rectifier 11 is composed of a three-phase bridge circuit when the AC power source 2 supplies three-phase AC power, and is composed of a single-phase bridge circuit when the AC power source 2 supplies single-phase AC power. In the example shown in the figure, since the AC power source 2 is set as a three-phase AC power source, the rectifier 11 is composed of a three-phase bridge circuit. As examples of the rectifier 11, there are diode rectifiers, 120-degree power-on rectifiers, and PWM switch control rectifiers. For example, when the rectifier 11 is a 120-degree power-on rectifier and a PWM switch control rectifier, the rectifier 11 is composed of a bridge circuit of a switching element and a diode connected in anti-parallel to the switching element, and each switching element is controlled to be on and off according to a drive instruction received from a superior control device (not shown), so as to perform power conversion in both AC and DC directions. In this case, examples of the switching element include FET, IGBT, thyristor, GTO (Gate Turn-OFF thyristor), transistor, etc., but other semiconductor elements may also be used. In addition, an AC reactor, AC line filter, etc. are sometimes provided on the AC input side of the rectifier 11, but are not shown here.

[0025] The electromagnetic contactor 18 as the first opening and closing part is provided on the AC input side of the rectifier 11, and is used to open and close the current path of the input current from the AC input side to the rectifier 11. The closing action of forming the current path of the input current from the AC input side to the rectifier 11 is achieved by closing the contacts of the electromagnetic contactor 18, and the opening action of cutting off the current path of the input current from the AC input side to the rectifier 11 is achieved by disconnecting the contacts of the electromagnetic contactor 18. In addition, a semiconductor switching element that opens and closes the current path of the input current from the AC input side to the rectifier 11 may be used instead of the electromagnetic contactor 18 as the first opening and closing part.

[0026] The circuit breaker 19 as the second opening and closing unit is provided between the AC power source 2 as the supply source of the AC power input to the rectifier 11 and the electromagnetic contactor 18, and is used to open and close the current path from the AC power source 2 to the electromagnetic contactor 18. The closing action of forming the current path from the AC power source 2 to the electromagnetic contactor 18 is achieved by closing the contacts of the circuit breaker 19, and the opening action of cutting off the current path from the AC power source 2 to the electromagnetic contactor 18 is achieved by disconnecting the contacts of the circuit breaker 19. In addition, a semiconductor switching element that opens and closes the current path from the AC power source 2 to the electromagnetic contactor 18 may be used instead of the circuit breaker 19 as the second opening and closing unit.

[0027] A DC link capacitor 20 is provided in a DC link connecting the DC output side of the rectifier 11 and the DC input side of the inverter 12. The DC link capacitor 20 has a function of storing DC power for the inverter 12 to generate AC power and a function of suppressing a pulsating portion of the DC output of the rectifier 11. Examples of the DC link capacitor 20 include an electrolytic capacitor, a film capacitor, and the like.

[0028] The inverter 12 is connected to the rectifier 11 via a DC link, and converts the DC power in the DC link into AC power for motor driving and outputs it. The inverter 12 only needs to have a structure capable of converting DC power into AC current, for example, there is a PWM control inverter with a switching element inside. When the motor 3 is a three-phase AC motor, the inverter 12 is configured as a three-phase bridge circuit, and when the motor 3 is a single-phase motor, the inverter 12 is configured by a single-phase bridge circuit. In the example shown in the figure, since the motor 3 is set as a three-phase AC motor, the inverter 12 is configured by a three-phase bridge circuit. When the inverter 12 is configured as a PWM control inverter, the inverter 12 is configured by a bridge circuit of a rectifier element and a switching element connected in anti-parallel to the rectifier element. In this case, as examples of the switching element, there are FET, IGBT, thyristor, GTO (Gate Turn-OFF thyristor), transistor, etc., but it can also be other semiconductor elements. The inverter 12 performs PWM control on the on-off action of the internal switching element based on the instruction of the upper control device (not shown) to convert the DC power in the DC link into AC power for motor driving and output it. The speed, torque or rotor position of the motor 3 is controlled based on the AC power supplied from the inverter 12. In addition, the inverter 12 can also convert the AC power regenerated by the motor 3 into DC power and return it to the DC link on the DC side by appropriately performing PWM control on the on-off action of the switching element.

[0029] The DC link voltage detection unit 13 detects the DC link voltage, which is the voltage between the terminals of the DC link. That is, the DC link voltage detection unit 13 detects the value of the potential difference between the positive potential appearing at the positive terminal on the DC output side of the rectifier 11 and the negative potential appearing at the negative terminal on the DC output side of the rectifier 11 as the DC link voltage. Alternatively, the DC link voltage detection unit 13 may detect the voltage applied between the positive and negative terminals of the DC link capacitor 20 as the DC link voltage. The value of the DC link voltage detected by the DC link voltage detection unit 13 is sent to the DC link voltage comparison unit 15.

[0030] The DC link voltage comparison unit 15 compares the DC link voltage with the first voltage threshold V th1 and the second voltage threshold V th2 The second voltage threshold V th2 is set to be higher than the first voltage threshold V th1 When the electromagnetic contactor 18 and the circuit breaker 19 are in the closed state and the AC power source 2 is not out of power, even if the motor drive device 1 drives the motor 3 normally without any fault (hereinafter referred to as the "normal state"), a slight pulsation will occur in the DC link voltage. The first voltage threshold Vth1 The second voltage threshold V is set to a value lower than the DC link voltage which is reduced by the pulsation in the normal state when the motor 3 is driven by the motor drive device 1. th2 The first voltage threshold V is set to a value higher than the DC link voltage which is increased by the pulsation in the normal state generated when the motor drive device 1 drives the motor 3. th1 and the second voltage threshold V th2 For example, the motor drive device 1 can be operated by experiment or actual application, or by computer simulation to obtain in advance the relationship between the application environment of the motor drive device 1, the voltage value on the DC output side of the rectifier 11, and the output of the alarm signal in the motor drive device 1, and the first voltage threshold V can be appropriately set on this basis. th1 and the second voltage threshold V th2 For example, the target value of the DC link voltage in a normal state is generally set according to the application environment of the motor drive device 1, so the first voltage threshold V th1 The second voltage threshold V is set to be lower than the target value by, for example, several tens of percent. th2 The first voltage threshold V is set to be higher than the target value by, for example, several tens of percent. The numerical value example shown here is only an example, and other values ​​may be used. th1 and the second voltage threshold V th2 , it may be stored in a rewritable storage unit (not shown) and can be rewritten by an external device, even if the first voltage threshold V is temporarily set. th1 and the second voltage threshold V th2 Afterwards, the first voltage threshold V th1 and the second voltage threshold V th2 Change to an appropriate value.

[0031] The DC link voltage converges to the first voltage threshold V th1 The second voltage threshold V th2 When the DC link voltage is within the range defined between , the DC link voltage is in a normal state. On the other hand, when the DC link voltage is lower than the first voltage threshold V th1 In the case where the DC link voltage is significantly reduced, when the DC link voltage is higher than the second voltage threshold V th2 In the case of , the DC link voltage is in a state where a large increase has occurred. The DC link voltage comparison unit 15 compares the DC link voltage with the first voltage threshold V th1 The DC link voltage is compared with the second voltage threshold V th2The comparison result obtained by the DC link voltage comparison unit 15 is sent to the abnormality detection unit 17 .

[0032] The input current detection unit 14 detects the input current input from the AC input side to the rectifier 11, that is, the input current input from the electromagnetic contactor 18 to the AC input side of the rectifier 11. In the example shown in the figure, the AC power supply 2 is a three-phase AC power supply, so the input current of the three-phase AC flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11, but the input current detection unit 14 detects the input current of two phases of the three phases, for example. As an alternative example, the input current detection unit 14 can also detect the input current of a single phase or three phases of the three phases. The value of the input current detected by the input current detection unit 14 is sent to the current comparison unit 16.

[0033] The current comparison unit 16 compares the input current with the current threshold I th For comparison. Current threshold I th It is used to determine whether there is input current flowing from the electromagnetic contactor 18 to the AC input side of the rectifier 11. th For example, the motor drive device 1 can be operated by experiment or actual operation, or by computer simulation to obtain the application environment of the motor drive device 1, the magnitude of the input current flowing from the electromagnetic contactor 18 to the AC input side of the rectifier 11, etc., and the current threshold value I can be appropriately set on this basis. th As an example, the current threshold I may be set to 1 in consideration of the detection error of the input current detection unit 14. th The value is set to be, for example, a percentage of the rated input current. The numerical value example shown here is only an example, and other values ​​may be used. th In the case of , it means that no input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11. th In the above case, it means that input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11. The comparison result obtained by the current comparison unit 16 is sent to the abnormality detection unit 17. th , it may be stored in a rewritable storage unit (not shown) and can be rewritten by an external device, even if the current threshold I is temporarily set. th Afterwards, the current threshold I can be adjusted as needed. th Change to an appropriate value.

[0034] In addition, as shown in the example of the figure, the input current detection unit 14 detects the input current of the two phases, so the current comparison unit 16 compares the input current of each phase of the two phases with the current threshold value I thIf the input current of at least one of the two phases is lower than the current threshold I th , the current comparison unit 16 determines that the input current is lower than the current threshold I th As an alternative example, the current comparison unit 16 may convert the two-phase input current detected by the input current detection unit 14 into a vector norm on the two-phase coordinates. If the vector norm is lower than the current threshold value I th , the current comparison unit 16 determines that the input current is lower than the current threshold I th ”.

[0035] When the input current detection unit 14 detects the input current of the three phases, the current comparison unit 16 compares the input current of each phase of the three phases with the current threshold value I th If the input current of at least one of the three phases is lower than the current threshold I th , the current comparison unit 16 determines that the input current is lower than the current threshold I th As an alternative example, the current comparison unit 16 may convert the three-phase detected by the input current detection unit 14 into a vector norm on a two-phase coordinate obtained by performing a two-phase transformation, and the vector norm is lower than the current threshold value I th In the case of the current comparison unit 16 determining that the input current is lower than the current threshold value I th ”.

[0036] When the input current detection unit 14 detects a single-phase input current, the current comparison unit 16 compares the single-phase input current with the current threshold value I th If the single-phase input current is lower than the current threshold I th , the current comparison unit 16 determines that the input current is lower than the current threshold I th ”.

[0037] When the DC link voltage comparison unit 15 determines that the DC link voltage is lower than the first voltage threshold V th1 Or it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of the abnormality detection unit 17, when the current comparison unit 16 determines that the input current is lower than the current threshold value I th1 When the first abnormality is determined to have occurred, the current comparison unit 16 determines that the input current is the current threshold value I th1 In the above cases, it is determined that the second abnormality has occurred.

[0038] The "first abnormality" as one of the determination results of the abnormality detection unit 17 includes at least one of a long-term power failure of the AC power source 2, an instantaneous power failure of the AC power source 2, an open state in which the electromagnetic contactor 18 as the first opening and closing unit opens the current path, and an open state in which the circuit breaker 19 as the second opening and closing unit opens the current path. th1 In the case of a long-term power outage of the AC power source 2, an instantaneous power outage of the AC power source 2, an open state in which the electromagnetic contactor 18 as the first opening and closing part opens the current path, and an open state in which the circuit breaker 19 as the second opening and closing part opens the current path, a state in which no input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11 occurs. Therefore, in the present embodiment, when it is determined that the DC link voltage is lower than the first voltage threshold V th1 Or it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of the input current being determined to be lower than the current threshold I th1 When (that is, when no input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11), the abnormality detection unit 17 determines that the first abnormality has occurred. In addition, in general interpretation, the disconnected state of the electromagnetic contactor 18 and the circuit breaker 19 disconnecting the current path is rarely identified as "abnormal". In this embodiment, the "disconnected state of the electromagnetic contactor 18 and the circuit breaker 19 disconnecting the current path" may become a cause of a significant drop or increase in the DC link voltage, so the "disconnected state of the electromagnetic contactor 18 and the circuit breaker 19 disconnecting the current path" is also included in the definition of the "first abnormality".

[0039] The “second abnormality” as one of the determination results of the abnormality detection unit 17 includes at least one of a failure of the motor drive device 1, an overload on the motor drive device 1, and insufficient capacity of the AC power supply 2. th1In the above case, input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11. Although input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11, the reason for the significant drop or rise of the DC link voltage is first considered to be a fault of the motor drive device 1 itself. In addition, when an appropriate load is connected to the inverter 12 in the motor drive device 1, the AC power introduced from the AC power source 2 to the rectifier 11 and the AC power supplied from the inverter 12 to the load (motor 3) are balanced, and the DC link voltage should be a constant value like the target value although it pulsates slightly. However, when an overload is connected to the inverter 12 in the motor drive device 1, the AC power introduced from the AC power source 2 to the rectifier 11 and the AC power supplied from the inverter 12 to the load (motor 3) are unbalanced, and the DC power stored in the DC link capacitor 20 is consumed more than usual. In addition, even when the capacity of the AC power source 2 is insufficient for the motor drive device 1, the AC power introduced from the AC power source 2 to the rectifier 11 and the AC power supplied from the inverter 12 to the load (motor 3) are unbalanced, and the DC power stored in the DC link capacitor 20 is consumed more than usual. When this DC power is consumed more than usual, the DC link voltage also drops significantly. Therefore, in the present embodiment, when it is determined that the DC link voltage is lower than the first voltage threshold V th1 Or it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of the input current being determined to be the current threshold I th1 In the above case (that is, when input current flows from the electromagnetic contactor 18 to the AC input side of the rectifier 11 ), the abnormality detection unit 17 determines that the second abnormality has occurred.

[0040] The display unit 23 displays the determination result of the abnormality detection unit 17. Examples of the display unit 23 include displays such as a display, a personal computer, a portable terminal, and a touch panel, but these may also be attached devices of the motor drive device 1 or attached devices in its upper control device. For example, a display such as "a first abnormality has occurred" or "a second abnormality has occurred" is performed. In addition, the display unit 23 may not display or may display "normal" during the period when neither "a first abnormality has occurred" nor "a second abnormality has occurred" is displayed. In addition, regarding "a first abnormality has occurred", the display unit 23 may also display in more detail such as "a long-term power failure of the AC power supply, an instantaneous power failure of the AC power supply, a disconnected state of the electromagnetic contactor disconnecting the current path, a disconnected state of the circuit breaker disconnecting the current path", etc. Similarly, regarding "a second abnormality has occurred", the display unit 23 may also display in more detail such as "a failure of the motor drive device, an overload on the motor drive device, or a capacity shortage of the AC power supply". The above-mentioned display example displayed by the display unit 23 is only an example, and "a first abnormality has occurred", "a second abnormality has occurred" and "normal" may also be displayed based on other expressions and patterns. As an alternative example, the display unit 23 may be replaced by an audio device that emits sound, such as a sound, a speaker, a buzzer, a bell, etc. In the case where the operator is informed of the determination result of the abnormality detection unit 17 by an audio device, for example, the timbre, scale, rhythm or melody may be set in a different manner that can distinguish "a first abnormality has occurred" from "a second abnormality has occurred". In this case, it is preferred that the audio device is set to be silent during the period when "a first abnormality has occurred" and "a second abnormality has occurred" are not notified. In addition, alternatively, a method of using a printer to print on paper or the like for display may be adopted. In addition, alternatively, these methods may be appropriately combined to achieve the purpose.

[0041] According to this embodiment, the operator can easily and accurately determine the cause of the DC link voltage drop or increase based on the determination result of the abnormality detection unit 17. In addition, the operator can quickly take accurate measures according to the cause of the DC link voltage drop or increase.

[0042] For example, when the abnormality detection unit 17 determines that the voltage of the DC link has dropped or increased significantly, the operator can understand that the cause of the significant drop or rise in the voltage of the DC link is at least one of the long-term power failure of the AC power source 2, the instantaneous power failure of the AC power source 2, the open state of the electromagnetic contactor 18 as the first opening and closing unit opening the current path, and the open state of the circuit breaker 19 as the second opening and closing unit opening the current path. Therefore, although the motor drive device 1 is normal, the operator will not mistakenly identify it as a fault, so the normal motor drive device 1 itself will not be replaced or the components in the motor drive device 1 will not be replaced or repaired. In addition, the operator can immediately start the operation of confirming the opening and closing of the electromagnetic contactor 18 and the circuit breaker 19. When it is confirmed that the electromagnetic contactor 18 and the circuit breaker 19 are in the open state, the operation of restoring the electromagnetic contactor 18 and the circuit breaker 19 can be quickly started. In addition, when the operator confirms that the electromagnetic contactor 18 and the circuit breaker 19 are in the closed state, it is possible to take measures such as restoring the AC power source 2 or waiting until the AC power source 2 is restored.

[0043] For example, when the abnormality detection unit 17 determines that the DC link voltage has dropped or increased significantly, the operator can understand that the cause of the significant drop or increase in the DC link voltage is at least one of a failure of the motor drive device 1, an overload on the motor drive device 1, and insufficient capacity of the AC power source 2. Therefore, the operator can immediately start to confirm the load state of the motor drive device 1 and the capacity of the AC power source 2. When it is confirmed that the cause of the significant drop or increase in the DC link voltage is an overload on the motor drive device 1 and insufficient capacity of the AC power source 2, the operator can immediately start to make countermeasures such as design changes to the motor drive device 1 and equipment enhancement of the AC power source 2. In addition, when the operator confirms that there is no problem with the load state of the motor drive device 1 and the capacity of the AC power source 2, it can be understood that it is a failure of the motor drive device 1, so the replacement operation of the motor drive device 1 itself or the replacement operation or repair operation of the components in the motor drive device 1 can be efficiently performed.

[0044] The DC link voltage comparison unit 15, the current comparison unit 16, and the abnormality detection unit 17 (including the case of the modified example described later) can be constructed, for example, in the form of a software program, or can be constructed by a combination of various electronic circuits and software programs, or can be composed of various electronic circuits alone. For example, when the DC link voltage comparison unit 15, the current comparison unit 16, and the abnormality detection unit 17 (including the case of the modified example described later) are constructed in the form of a software program, the functions of the above-mentioned units can be realized by making a calculation processing device such as DSP, FPGA, etc. operate according to the software program. In addition, or, the DC link voltage comparison unit 15, the current comparison unit 16, and the abnormality detection unit 17 (including the case of the modified example described later) can be realized as a semiconductor integrated circuit in which a software program for realizing the functions of each unit is written. In addition, or, the DC link voltage comparison unit 15, the current comparison unit 16, and the abnormality detection unit 17 (including the case of the modified example described later) can be realized as a recording medium in which a software program for realizing the functions of each unit is written. The DC link voltage comparison unit 15 , the current comparison unit 16 , and the abnormality detection unit 17 (including the case of a modified example described later) may be provided in, for example, a numerical control device of a machine tool or a robot controller that controls a robot.

[0045] In addition, the DC link voltage detection unit 13 and the input current detection unit 14 may be formed by a combination of an analog circuit and a digital circuit, or may be realized by a calculation processing device constructed in the form of a software program, or may be formed only by an analog circuit. In addition, regarding the DC link voltage detection unit 13 and the input current detection unit 14, components generally provided in the motor drive device 1 may be used.

[0046] In addition, the first voltage threshold V is stored th1 , the second voltage threshold V th2 And the current threshold I th The storage unit may be composed of an electrically erasable / recordable nonvolatile memory such as EEPROM (registered trademark) or a high-speed readable and writable random access memory such as DRAM or SRAM.

[0047] Figure 2 1 is a flowchart showing the operation flow of the motor drive device according to one embodiment of the present disclosure.

[0048] When the motor 3 is driven by the motor driving device 1 , the DC link voltage detection unit 13 detects a DC link voltage as a voltage between DC link terminals in step S101 . The value of the DC link voltage detected by the DC link voltage detection unit 13 is sent to the DC link voltage comparison unit 15 .

[0049] In step S102, the input current detector 14 detects the input current input from the AC input side to the rectifier 11, that is, the input current input from the electromagnetic contactor 18 to the AC input side of the rectifier 11. The value of the input current detected by the input current detector 14 is sent to the current comparator 16.

[0050] Furthermore, the DC link voltage detection process of step S101 and the input current detection process of step S102 may be executed in reverse order.

[0051] In step S103, the DC link voltage comparison unit 15 compares the DC link voltage with the first voltage threshold V th1 Compare and determine whether the DC link voltage is lower than the first voltage threshold V th1 In step S103, it is determined that the DC link voltage is lower than the first voltage threshold V th1 In the case of a DC link voltage being a first voltage threshold V th1 In the above case, the process returns to step S101 . The comparison result obtained by the DC link voltage comparison unit 15 in step S103 is sent to the abnormality detection unit 17 .

[0052] In step S104, the DC link voltage comparison unit 15 compares the DC link voltage with the second voltage threshold V th2 Compare and determine whether the DC link voltage is higher than the second voltage threshold V th2 In step S104, it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of , the process proceeds to step S105, and when it is determined that the DC link voltage is the second voltage threshold V th2 In the following cases, the process returns to step S101 . The comparison result obtained by the DC link voltage comparison unit 15 in step S104 is sent to the abnormality detection unit 17 .

[0053] Furthermore, the DC link voltage comparison process of step S103 and the DC link voltage comparison process of step S104 may be executed in reverse order.

[0054] In step S105, the current comparison unit 16 compares the input current with the current threshold I th Compare and determine whether the input current is lower than the current threshold I th In step S105, it is determined that the input current is lower than the current threshold I th In the case of th In the above case, the process proceeds to step S107 . The comparison result obtained by the current comparison unit 16 in step S105 is sent to the abnormality detection unit 17 .

[0055] Furthermore, the input current detection process of step S102 may be performed between the DC link voltage comparison process of step S104 and the input current comparison process of step S105 .

[0056] In step S106, the abnormality detection unit 17 determines that a first abnormality has occurred. The first abnormality includes at least one of a long-term power failure of the AC power source 2, an instantaneous power failure of the AC power source 2, an open state in which the electromagnetic contactor 18 as the first opening and closing unit opens the current path, and an open state in which the circuit breaker 19 as the second opening and closing unit opens the current path.

[0057] In step S107 , the abnormality detection unit 17 determines that the second abnormality has occurred. The second abnormality includes at least one of a failure of the motor drive device 1 , an overload on the motor drive device 1 , and insufficient capacity of the AC power source 2 .

[0058] In addition, although Figure 2 Although not shown in the figure, after the abnormality determination processing in steps S106 and S107, the display unit 23 may display the determination result of the abnormality detection unit 17.

[0059] The series of processes of steps S101 to S107 described above are repeatedly executed in a predetermined cycle until, for example, the first abnormality or the second abnormality is detected by the abnormality detection unit 17 .

[0060] Next, refer to Figure 3 and Figure 4 A modified example of the motor drive device 1 according to an embodiment of the present disclosure is described. This modified example can further distinguish the instantaneous power failure of the AC power source 2, the long-term power failure of the AC power source 2, the disconnected state of the circuit breaker 19 as the second disconnection and closing unit disconnecting the current path, and the disconnected state of the electromagnetic contactor 18 as the first disconnection and closing unit disconnecting the current path included in the first abnormality.

[0061] Figure 3 FIG. 1 is a diagram showing a motor drive device according to a modified example of one embodiment of the present disclosure.

[0062] like Figure 3 As shown in FIG. 1 , the motor drive device 1 according to this modification further includes an input voltage detection unit 21 and an input voltage comparison unit 22. In addition, regarding the circuit components other than the input voltage detection unit 21, the input voltage comparison unit 22 and the abnormality detection unit 17, Figure 1 Since the circuit components shown are the same, the same circuit components are denoted by the same reference numerals and detailed description of the circuit components is omitted.

[0063] The input voltage detection unit 21 detects an input voltage, which is a phase voltage between the electromagnetic contactor 18 as a first opening and closing unit and the circuit breaker 19 as a second opening and closing unit. In the example shown in the figure, the AC power supply 2 is a three-phase AC power supply, so the phase voltage of each of the three phases between the electromagnetic contactor 18 and the circuit breaker 19 is detected. In the case where the AC power supply 2 is a single-phase AC power supply, the single-phase voltage between the electromagnetic contactor 18 and the circuit breaker 19 is detected. The value of the input voltage detected by the input voltage detection unit 21 is sent to the input voltage comparison unit 22.

[0064] When the DC link voltage comparison unit 15 determines that the DC link voltage is lower than the first voltage threshold V th1 Or it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of th3 In addition, the input voltage comparison unit 22 also determines in this comparison process that the input voltage is lower than the power failure threshold value V th3 The power failure threshold V th3 It is used to determine whether the AC power supply 2 has a long-term power outage or a momentary power outage. th3 For example, the motor drive device 1 can be operated through experiments or actual applications, or through computer simulations, to obtain in advance the application environment of the motor drive device 1, the AC voltage that can normally drive the motor 3 using the motor drive device 1, etc., and on this basis, the power failure threshold V can be appropriately set. th3 When taking an example, considering safety, the power failure threshold V th3 The power failure threshold V may be set to a value that is, for example, several tens of percent lower than the lower limit of the AC voltage of the AC power source 2 that can normally drive the motor 3 through the motor drive device 1. The numerical value example shown here is only an example, and other values ​​may be used. th3 , it may also be stored in a rewritable storage unit (not shown) and can be rewritten by an external device, even if the power failure threshold V is temporarily set. th3 Afterwards, the power outage threshold V th3 The comparison result obtained by the input voltage comparison unit 22 is sent to the abnormality detection unit 17. In addition, it is used to determine whether the input voltage is lower than the power failure threshold value V th3The above-mentioned "prescribed time" is set to a value that can divide the power outage of the AC power source 2 into instantaneous power outages (momentary outages) and long-term power outages other than the prescribed time. Generally speaking, the instantaneous power outages of the AC power source 2 mostly refer to power outages of less than several seconds, so the above-mentioned "prescribed time" can be set to about several seconds (for example, 2 seconds). The numerical example shown here is just an example, and other values ​​may be used. In addition, the above-mentioned "prescribed time" may also be stored in a rewritable storage unit (not shown), which can be rewritten by an external device, and even after the above-mentioned "prescribed time" is temporarily set, the above-mentioned "prescribed time" can be changed to an appropriate value as needed. The comparison result obtained by the input voltage comparison unit 22 is sent to the abnormality detection unit 17.

[0065] As described above, the input voltage detection unit 21 detects the input voltage as the phase voltage of each of the three phases, and therefore the input voltage comparison unit 22 compares the input voltage of each of the three phases with the power failure threshold value V th3 If the input voltage of at least one of the three phases is lower than the power failure threshold V th3 , the input voltage comparison unit 22 determines that the input voltage is lower than the power failure threshold V th3 As an alternative example, the input voltage comparison unit 22 may perform coordinate transformation on the three-phase input voltage to convert it into a voltage vector on a two-phase coordinate, and the amplitude of the voltage vector is lower than the power failure threshold value V th3 In the case of a power failure, the input voltage comparison unit 22 determines that the input voltage is lower than the power failure threshold value V th3 ”.

[0066] When the input voltage comparison unit 22 determines that the input voltage is at the power failure threshold value V th3 When the following state continues for less than a predetermined time, the abnormality detection unit 17 determines that an instantaneous power failure of the AC power supply 2 has occurred. In addition, when the input voltage comparison unit 22 determines that the input voltage is the power failure threshold value V th3 If the following state continues for more than a predetermined time, the abnormality detection unit 17 determines that either the circuit breaker 19 as the second opening and closing unit disconnects the current path or a long-term power outage of the AC power source 2 has occurred. In addition, if the input voltage comparison unit 22 determines that the input voltage is higher than the power outage threshold value V th3 In the case of , the abnormality detection unit 17 determines that the electromagnetic contactor 18 as the first opening and closing unit has opened the current path. The determination result obtained by the abnormality detection unit 17 is displayed on the display unit 23.

[0067] For example, when the abnormality detection unit 17 determines that "an instantaneous power outage of the AC power source 2 has occurred", the operator can take measures such as waiting until the AC power source 2 is restored. For example, when the abnormality detection unit 17 determines that "one of the disconnected state in which the circuit breaker 19 disconnects the current path or the long-term power outage of the AC power source 2 has occurred", the operator can immediately start the operation of confirming the opening and closing of the circuit breaker 19. When it is confirmed that the circuit breaker 19 is in the disconnected state, the operation of restoring the circuit breaker 19 can be quickly started. In addition, when the operator confirms that the circuit breaker 19 is in the closed state, the operator can take measures such as restoring the AC power source 2 or waiting until the AC power source 2 is restored. For example, when the abnormality detection unit 17 determines that "an disconnected state in which the electromagnetic contactor 18 disconnects the current path has occurred", the operator can immediately start the operation of restoring the electromagnetic contactor 18.

[0068] Thus, according to this modification, it is possible to further distinguish the instantaneous power failure of the AC power source 2, the long-term power failure of the AC power source 2, the disconnected state of the circuit breaker 19 as the second disconnection and closing unit disconnecting the current path, and the disconnected state of the electromagnetic contactor 18 as the first disconnection and closing unit disconnecting the current path included in the first abnormality. In addition, in this modification, it is also possible to distinguish the DC link voltage comparison unit 15 from the first voltage threshold value V th1 Or it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of "when the current comparison unit 16 determines that the input current is the current threshold value I th When the error is greater than 0.05, the abnormality detection unit 17 determines that a second abnormality has occurred.

[0069] The input voltage comparison unit 22 can be constructed, for example, in the form of a software program, or can be constructed by a combination of various electronic circuits and software programs, or can also be composed only of various electronic circuits. For example, when the input voltage comparison unit 22 is constructed in the form of a software program, the functions of the above-mentioned units can be realized by making a calculation processing device such as a DSP, FPGA, etc. operate according to the software program. In addition, or, the input voltage comparison unit 22 can also be implemented as a semiconductor integrated circuit written with a software program for realizing the functions of each unit. In addition, or, the input voltage comparison unit 22 can also be implemented as a recording medium written with a software program for realizing the functions of each unit. In addition, the input voltage comparison unit 22 can be set in a numerical control device of a machine tool, or in a robot controller that controls a robot.

[0070] In addition, the input voltage detection unit 21 can be formed by a combination of analog circuits and digital circuits, or can be implemented by a calculation processing device constructed in the form of a software program, or can be formed only by an analog circuit. In addition, regarding the input voltage detection unit 21, a component generally provided in the motor drive device 1 can also be used.

[0071] In addition, the power failure threshold V is stored th3 The storage unit for the above-mentioned "specified time" used to determine whether the power outage of the AC power supply 2 is an instantaneous power outage can be composed of an electrically erasable / recordable non-volatile memory such as EEPROM (registered trademark) or a random access memory that can be read and written at high speed such as DRAM, SRAM, etc.

[0072] Figure 4 1 is a flowchart showing the operation flow of the motor drive device according to a modified example of one embodiment of the present disclosure.

[0073] When the motor 3 is driven by the motor driving device 1 , the DC link voltage detection unit 13 detects a DC link voltage as a voltage between DC link terminals in step S201 . The value of the DC link voltage detected by the DC link voltage detection unit 13 is sent to the DC link voltage comparison unit 15 .

[0074] In step S202, the input current detector 14 detects the input current input from the AC input side to the rectifier 11, that is, the input current input from the electromagnetic contactor 18 to the AC input side of the rectifier 11. The value of the input current detected by the input current detector 14 is sent to the current comparator 16.

[0075] In step S203 , the input voltage detector 21 detects an input voltage that is a phase voltage between the electromagnetic contactor 18 as a first opening / closing unit and the circuit breaker 19 as a second opening / closing unit. The value of the input voltage detected by the input voltage detector 21 is sent to the input voltage comparison unit 22 .

[0076] Furthermore, the DC link voltage detection process of step S201 , the input current detection process of step S202 , and the input voltage detection process of step S203 may be executed in reverse order.

[0077] In step S204, the DC link voltage comparison unit 15 compares the DC link voltage with the first voltage threshold V th1 Compare and determine whether the DC link voltage is lower than the first voltage threshold V th1 In step S204, it is determined that the DC link voltage is lower than the first voltage threshold V th1 In the case of , the process proceeds to step S205, and when it is determined that the DC link voltage is the first voltage threshold Vth1 In the above case, the process returns to step S201 . The comparison result obtained by the DC link voltage comparison unit 15 in step S204 is sent to the abnormality detection unit 17 .

[0078] In step S205, the DC link voltage comparison unit 15 compares the DC link voltage with the second voltage threshold V th2 Compare and determine whether the DC link voltage is higher than the second voltage threshold V th2 In step S205, it is determined that the DC link voltage is higher than the second voltage threshold V th2 In the case of , the process proceeds to step S206. When it is determined that the DC link voltage is the second voltage threshold V th2 In the following cases, the process returns to step S201 . The comparison result obtained by the DC link voltage comparison unit 15 in step S205 is sent to the abnormality detection unit 17 .

[0079] Furthermore, the DC link voltage comparison process of step S204 and the DC link voltage comparison process of step S205 may be executed in reverse order.

[0080] In step S206, the current comparison unit 16 compares the input current with the current threshold I th Compare and determine whether the input current is lower than the current threshold I th In step S206, it is determined that the input current is lower than the current threshold I th In the case of th In the above case, the process proceeds to step S207 . The comparison result obtained by the current comparison unit 16 in step S206 is sent to the abnormality detection unit 17 .

[0081] Furthermore, the input current detection process of step S202 may be performed between the DC link voltage comparison process of step S205 and the input current comparison process of step S206 .

[0082] In step S208, the input voltage comparison unit 22 compares the input voltage with the power failure threshold V th3 Compare and determine whether the input voltage is higher than the power-off threshold V th3 In step S208, it is determined that the input voltage is higher than the power failure threshold V th3 In the case of a power failure, the process proceeds to step S209. If the input voltage is determined to be at the power failure threshold V th3 In the following cases, the process proceeds to step S210 . The comparison result obtained by the input voltage comparison unit 22 in step S208 is sent to the abnormality detection unit 17 .

[0083] In step S210, the input voltage comparison unit 22 compares the input voltage with the power failure threshold V th3Compare and determine the input voltage to be the power failure threshold V th3 In step S210, it is determined that the input voltage is at the power failure threshold V th3 If the following state continues for a predetermined time or longer, the process proceeds to step S211, where it is determined that the input voltage is at the power failure threshold V th3 When the following state continues for less than the prescribed time, the process proceeds to step S212.

[0084] In step S207 , the abnormality detection unit 17 determines that the second abnormality has occurred. The second abnormality includes at least one of a failure of the motor drive device 1 , an overload on the motor drive device 1 , and insufficient capacity of the AC power source 2 .

[0085] In step S209 , the abnormality detection unit 17 determines that the open state in which the electromagnetic contactor 18 as the first opening and closing unit opens the current path has occurred.

[0086] In step S211 , the abnormality detection unit 17 determines that either the circuit breaker 19 as the second opening and closing unit is in an open state in which the current path is opened or a long-term power outage of the AC power source 2 has occurred.

[0087] In step S212 , the abnormality detection unit 17 determines that an instantaneous power failure of the AC power source 2 has occurred.

[0088] In addition, although Figure 4 Although not shown in the figure, after the abnormality determination processing in steps S207, S209, S211, and S212, the display unit 23 may display the determination result of the abnormality detection unit 17.

[0089] The series of processes of steps S201 to S212 described above are repeatedly executed in a prescribed cycle until, for example, a long-term power outage of the AC power supply 2, a momentary power outage of the AC power supply 2, a disconnected state of the electromagnetic contactor 18 disconnecting the current path, a disconnected state of the circuit breaker 19 disconnecting the current path, or a second abnormality is detected by the abnormality detection unit 17.

[0090] According to one aspect of the present disclosure, in a motor drive device in which a rectifier and an inverter are connected via a DC link, the cause of a significant drop or increase in the DC link voltage can be easily and accurately determined.

Claims

1. A motor drive device comprising: A rectifier that converts AC power input from the AC input side into DC power and outputs it to a DC link as a DC output side; An inverter that converts the DC power in the DC link into AC power for motor driving and then outputs it; a DC link voltage detection unit configured to detect a DC link voltage as a voltage between terminals of the DC link; an input current detection unit configured to detect an input current input from the AC input side of the rectifier; a DC link voltage comparison unit, which compares the DC link voltage with a first voltage threshold and a second voltage threshold, respectively, wherein the second voltage threshold is set to a value higher than the first voltage threshold; a current comparison unit, which compares the input current with a current threshold; as well as An abnormality detection unit, when the DC link voltage comparison unit determines that the DC link voltage is lower than the first voltage threshold or determines that the DC link voltage is higher than the second voltage threshold, the abnormality detection unit determines that a first abnormality has occurred when the current comparison unit determines that the input current is lower than the current threshold, and determines that a second abnormality has occurred when the current comparison unit determines that the input current is greater than the current threshold.

2. The motor drive device according to claim 1, further comprising: a first opening and closing unit, which is provided at the AC input side of the rectifier and is used to open and close the current path of the input current from the AC input side to the rectifier; and The second opening and closing unit is provided between an AC power source as a supply source of AC power input to the rectifier and the first opening and closing unit, and is used to open and close a current path from the AC power source to the first opening and closing unit.

3. The motor drive device according to claim 2, wherein: The first abnormality includes at least one of a long-term power failure of the AC power source, an instantaneous power failure of the AC power source, an open state in which the first opening and closing unit opens the current path, and an open state in which the second opening and closing unit opens the current path. The second abnormality includes at least one of a failure of the motor drive device, an overload on the motor drive device, and insufficient capacity of the AC power source.

4. The motor drive device according to claim 3, further comprising: an input voltage detection unit configured to detect an input voltage, the input voltage being a phase voltage between the first opening / closing unit and the second opening / closing unit; and an input voltage comparison unit, which compares the input voltage with a power failure threshold value when the DC link voltage comparison unit determines that the DC link voltage is lower than the first voltage threshold value or determines that the DC link voltage is higher than the second voltage threshold value, When the input voltage comparison unit determines that the input voltage is less than or equal to the power failure threshold value for less than a predetermined time, the abnormality detection unit determines that an instantaneous power failure of the AC power source has occurred. When the input voltage comparison unit determines that the input voltage is below the power outage threshold for more than the specified time, the abnormality detection unit determines that one of the opening state of the second opening and closing unit opening the current path and the long-term power outage of the AC power supply has occurred.

5. The motor drive device according to claim 4, wherein: When the input voltage comparison unit determines that the input voltage is higher than the power failure threshold, the abnormality detection unit determines that an open state has occurred in which the first opening / closing unit opens a current path.

6. The motor drive device according to any one of claims 2 to 5, wherein: The first opening and closing part is an electromagnetic contactor.

7. The motor drive device according to any one of claims 2 to 6, wherein: The second opening and closing part is a circuit breaker.

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