Motor drive device for calculating motor insulation resistance value

Abstract

This motor drive device comprises: an insulation resistance value detection unit for detecting the insulation resistance value of a motor on the basis of the measured value of the inter-terminal voltage of a measurement resistor and the resistance value of the measurement resistor; and a failure determination unit for determining, on the basis of the error between the measured and estimated values of the inter-terminal voltage of the measurement resistor, the presence or absence of a failure of the insulation resistance value detection unit for detecting the insulation resistance value of the motor.

Description

[Technical field]

[0001] The present invention relates to a motor drive device that calculates the insulation resistance value of a motor. [Background technology]

[0002] In servo motors installed in machine tools, the insulation resistance value (insulation resistance value) of the motor coil (winding) against the ground decreases due to the infiltration of oil over time. When the insulation resistance value of the motor coil decreases, a leakage current flows in the closed circuit consisting of the motor, the motor drive device, and the ground. When the leakage current flows in the motor drive device in addition to the normal motor drive current, the servo amplifier performs an overcurrent detection operation and the breaker installed in the input stage trips. As a result, the machine tool in which the motor is installed will come to an emergency stop. When such an emergency stop occurs, the machine tool may be stopped for a long period of time to determine the cause, which reduces efficiency. For this reason, the task of measuring the insulation resistance value of the motor is essential for the operation of the motor drive device.

[0003] For example, there is known a method for detecting insulation resistance deterioration of a motor driven by a motor drive device including a power supply unit that rectifies power supplied from an AC power source via a switch in a rectifier circuit and smoothes it with a capacitor, and a motor drive amplifier that converts the DC voltage from the power supply unit into AC to drive the motor, the method comprising turning off the switch to stop operation of the motor, connecting one end of the capacitor to the ground and connecting the other end to the motor coil, detecting the current flowing in the closed circuit formed by the capacitor, the motor coil, and the ground, and detecting insulation resistance deterioration of the motor (see, for example, Patent Document 1).

[0004] For example, the present invention may include a power supply unit that rectifies an AC voltage supplied from an AC power supply via a switch into a DC voltage using a rectifier circuit and smoothes the rectified DC voltage using a capacitor, a motor drive amplifier unit that converts the DC voltage from the power supply unit into an AC voltage using upper arm and lower arm switching elements to drive a motor, a power supply voltage measurement unit that measures the voltage of the power supply unit, a contact unit that connects one end of the capacitor to the ground, and a current detection unit that is provided between the other end of the capacitor and a motor coil, and the switch is turned off and the contact unit is turned on, and the contact unit, the capacitor, the motor, and the motor are connected to the ground by the current detection unit. A motor drive device equipped with a failure detection function for an insulation resistance deterioration detection unit of a motor, characterized in that it comprises: an insulation resistance deterioration detection unit that detects whether or not the insulation resistance of the motor has deteriorated based on a detection signal obtained from a closed circuit formed by a motor coil and the ground; and a failure detection unit that changes the contact unit from an on state to an off state, arbitrarily switches a switching element of an upper arm or a lower arm of the motor drive amplifier unit, and detects whether or not the insulation resistance deterioration detection unit has a failure based on the detection signal in the insulation resistance deterioration detection unit and a voltage value measured by the power supply voltage measurement unit (see, for example, Patent Document 2).

[0005] For example, a device for detecting insulation deterioration of a motor connected to a motor drive device having a converter unit having a rectifier circuit that rectifies an AC power supply, a smoothing capacitor that smoothes the output of the rectifier circuit, and a plurality of inverter units that convert DC from the converter unit to AC to drive a plurality of motors, the device including: a first switch that, when insulation deterioration is detected, is brought into conduction to ground one end of the smoothing capacitor; a voltage detection unit that measures the voltage across the smoothing capacitor; a plurality of second switches that, when insulation deterioration is detected, are brought into conduction to connect the other end of the smoothing capacitor to windings of the plurality of motors, respectively; a plurality of current detection units that, when the first switch and the plurality of second switches are brought into conduction, respectively detect the discharge current of the smoothing capacitor that flows through the insulation resistance of each of the plurality of motors; A motor insulation deterioration detection device is known that includes a plurality of insulation resistance calculation units that calculate the insulation resistance of each of the plurality of motors from the current detected by each of the current detection units, wherein the one first switch and the one voltage detection unit are provided in the converter unit, the plurality of second switches, the plurality of current detection units, and the plurality of insulation resistance calculation units are provided in the plurality of inverter units, respectively, and the device includes communication means that transmits from the converter unit to the plurality of inverter units a voltage value detected by the one voltage detection unit and a signal notifying the timing of turning on the one first switch, and wherein connection by the second switch, detection of current by the current detection unit, and calculation of insulation resistance by the insulation resistance calculation unit are performed simultaneously at the same timing in each of the plurality of inverter units (see, for example, Patent Document 3).

[0006] For example, a motor drive device is known which comprises: a rectifier circuit which rectifies an AC voltage supplied from an AC power supply via a first switch into a DC voltage; a power supply unit which smoothes the DC voltage rectified by the rectifier circuit with a capacitor; an inverter unit which converts the DC voltage smoothed by the power supply unit into an AC voltage by the switching operation of a semiconductor switching element to drive a motor; a current detection unit which measures a current value flowing through a resistor having one end connected to a coil of the motor and the other end connected to one terminal of the capacitor; a voltage detection unit which measures a voltage value across the capacitor; a second switch which grounds the other terminal of the capacitor; and an insulation resistance detection unit which stops operation of the motor, turns off the first switch, and detects an insulation resistance value of the motor, which is the resistance between the motor coil and the ground, using two sets of the current values ​​and the voltage values ​​measured in two states, namely, a state in which the second switch is turned off and a state in which the second switch is turned on (see, for example, Patent Document 4).

[0007] For example, there is known an insulation detector connected between one of a P bus and an N bus of an electric device including a rectifier circuit that is arranged between an AC power source and a load and converts an AC voltage from the AC power source into a DC voltage, and an inverter connected downstream of the rectifier circuit to drive the load, and an output line that connects the inverter and the load, the insulation detector comprising: a resistor formed by connecting a detection resistor and a voltage dividing resistor in series; a capacitor connected in parallel to the resistor and having an impedance lower than that of the detection resistor; and a voltage detector that measures a voltage value across the insulation detector by detecting the voltage across the detection resistor divided by the voltage dividing resistor, and the insulation detector detects the insulation resistance between the load and the ground or the housing from the voltage value across the insulation detector measured by the voltage detector without being disconnected from the AC power source (see, for example, Patent Document 5). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 4554501 [Patent Document 2] Patent No. 5832578 [Patent Document 3] Patent No. 4565036 [Patent Document 4] Patent No. 5788538 [Patent Document 5] JP 2017-142269 A Summary of the Invention [Problem to be solved by the invention]

[0009] If the insulation resistance detection circuit of a motor fails, the insulation resistance value cannot be measured accurately. Even if a failure detection circuit is provided to detect failures in the insulation resistance detection circuit itself, the insulation resistance detection circuit will gradually increase in measurement error due to aging before the failure detection circuit detects a failure in the insulation resistance detection circuit, making it increasingly difficult to measure the insulation resistance value accurately. Therefore, there is a need for a technology that can accurately detect the insulation resistance value of a motor while accurately detecting failures in the circuit that detects the insulation resistance value of a motor. [Means for solving the problem]

[0010] According to one aspect of the present disclosure, a motor drive device includes a first switch that opens and closes an electric path from an AC power source; a power supply unit that rectifies an AC voltage supplied from the AC power source via the first switch in a closed state into a DC voltage using a rectifier circuit and smoothes the rectified DC voltage using a capacitor; a motor drive amplifier unit that converts the DC voltage from the power supply unit into an AC voltage for driving the motor using switching elements in an upper arm and a lower arm and supplies the AC voltage to the motor; and a first voltage measurement unit that obtains a measured value of the voltage of the power supply unit. a voltage determination unit that determines whether a measured value of the voltage of the power supply unit acquired by the first voltage measurement unit is equal to or lower than a predetermined reference voltage;an insulation resistance value detection unit having a second switch that connects one end of the capacitor to the ground when in a closed state and does not connect one end of the capacitor to the ground when in an open state, a measurement resistor provided between the other end of the capacitor and the motor coil, a second voltage measurement unit that acquires a measured value of a voltage between the terminals of the measurement resistor, and a calculation unit that calculates an insulation resistance value of the motor based on the measured value of the voltage of the power supply unit acquired by the first voltage measurement unit, the measured value of the voltage between the terminals of the measurement resistor acquired by the second voltage measurement unit, and the resistance value of the measurement resistor when a first closed circuit including the second switch, the capacitor, the measurement resistor, the motor coil, and the ground is formed by opening the first switch and closing the second switch; a voltage estimation unit that calculates an estimate of the terminal-to-terminal voltage of the measurement resistor based on the measured value of the voltage of the power supply unit acquired by the first voltage measurement unit and the resistance value of the measurement resistor when a second closed circuit including the capacitor and the measurement resistor is formed by opening the first switch and the second switch and arbitrarily switching the switching elements of the upper arm or the lower arm of the motor drive amplifier unit; an error detection unit that detects an error between the measured value of the terminal-to-terminal voltage of the measurement resistor acquired by the second voltage measurement unit and the estimate value of the terminal-to-terminal voltage of the measurement resistor calculated by the voltage estimation unit when the second closed circuit is formed; and a failure determination unit that determines the presence or absence of a failure in the insulation resistance value detection unit based on the error detected by the error detection unit. If the error detected by the error detection unit is outside a range of a predetermined reference error, it is determined that the insulation resistance value detection unit has a fault, and if the error detected by the error detection unit is within the range of the reference error, it is determined that the insulation resistance value detection unit has no fault. The insulation resistance value detection unit includes a correction value generation unit that generates a correction value based on the error detected by the error detection unit that was used when the fault determination unit determined that the insulation resistance value detection unit had no fault, and a correction value generation unit that corrects the measured value of the voltage between the terminals of the measurement resistor obtained by the second voltage measurement unit when the first closed circuit is configured, using the correction value generated by the correction value generation unit, thereby generating a corrected measured value of the voltage between the terminals of the measurement resistor. the calculation unit detects an insulation resistance value of the motor based on the measured value of the voltage of the power supply unit acquired by the first voltage measurement unit when the first closed circuit is configured, the corrected measured value of the voltage between the terminals of the measurement resistor, and the resistance value of the measurement resistor, and the second voltage measurement unit acquires the measured value of the voltage between the terminals of the measurement resistor when the second closed circuit is configured after the voltage determination unit determines that the measured value of the voltage of the power supply unit acquired by the first voltage measurement unit becomes equal to or lower than a reference voltage when the first switch and the second switch are opened and the switching elements of the upper arm and the lower arm of the motor drive amplifier are turned off. do. Effect of the Invention

[0011] According to one aspect of the present disclosure, it is possible to realize a motor drive device that can accurately detect the insulation resistance value of a motor while accurately detecting a fault in a circuit that detects the insulation resistance value of the motor. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 illustrates a motor drive device according to an embodiment of the present disclosure. [Diagram 2] 11 is a diagram illustrating a second closed circuit that is configured when a process for determining whether or not there is a malfunction in an insulation resistance value detector is executed in a motor drive device according to an embodiment of the present disclosure. FIG. [Diagram 3] 10 is a flowchart showing an operation flow of a process for determining whether or not there is a malfunction in an insulation resistance value detection unit in a motor drive device according to an embodiment of the present disclosure. [Figure 4] 1 is a diagram illustrating a first closed circuit that is configured when an insulation resistance value detection process is performed by an insulation resistance value detection unit in a motor drive device according to an embodiment of the present disclosure. FIG. [Diagram 5] 1 is a flowchart (part 1) showing an operation flow of an insulation resistance value detection process by an insulation resistance value detection unit in a motor drive device according to an embodiment of the present disclosure. [Figure 6] 10 is a flowchart (part 2) illustrating an operation flow of an insulation resistance value detection process by an insulation resistance value detection unit in a motor drive device according to an embodiment of the present disclosure. [Figure 7] FIG. 4 is a circuit diagram showing a portion related to a first closed circuit. [Figure 8] FIG. 13 is a diagram illustrating a modified example of a motor drive device according to an embodiment of the present disclosure. [Figure 9] 13 is a flowchart showing an operation flow of a process for determining whether or not an insulation resistance value detector in a modified example of a motor drive device according to an embodiment of the present disclosure has a malfunction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A motor drive device for calculating the insulation resistance value of a motor will be described below with reference to the drawings. In each drawing, the same components are given the same reference symbols. In addition, the scale of these drawings is appropriately changed to facilitate understanding. In addition, the embodiment shown in the drawings is one example for carrying out the invention, and the invention is not limited to the illustrated embodiment.

[0014] FIG. 1 is a diagram illustrating a motor drive device according to an embodiment of the present disclosure.

[0015] As an example, a case where a motor 3 is controlled by a motor drive device 1 connected to an AC power source 2 is shown. In this embodiment, the type of the motor 3 is not particularly limited, and may be, for example, an induction motor or a synchronous motor. The number of phases of the AC power source 2 and the motor 3 is not particularly limited in this embodiment, and may be, for example, three-phase or single-phase. Machines in which the motor 3 is provided include, for example, machine tools, robots, forging machines, injection molding machines, industrial machines, various electrical appliances, trains, automobiles, and aircraft. Examples of the AC power source 2 include a three-phase AC 400V power source, a three-phase AC 200V power source, a three-phase AC 600V power source, and a single-phase AC 100V power source. In the illustrated example, the AC power source 2 and the motor 3 are each three-phase.

[0016] An insulation resistor 4 exists between the motor coil (winding) of the motor 3 and the ground. The insulation resistance value Rm [Ω] of the insulation resistor 4 is infinite when there is no degradation, and as degradation progresses, it gradually decreases from infinity to several MΩ, several hundred kΩ, and so on. A motor drive device 1 according to an embodiment of the present disclosure has a function of detecting the insulation resistance value Rm [Ω] of the motor 3, and a function of determining whether or not there is a failure in the function of detecting the insulation resistance value Rm [Ω].

[0017] As shown in FIG. 1, a motor driving device 1 according to one embodiment of the present disclosure includes a first switch 11, a power supply unit 12, a motor driving amplifier unit 13, a first voltage measurement unit 14, an insulation resistance value detection unit 15, a voltage estimation unit 16, an error detection unit 17, and a fault determination unit 18.

[0018] The first switch 11 opens and closes an electric path between the AC power source 2 and the rectifier circuit 21 in the power source unit 12. The opening and closing of the electric path by the first switch 11 is controlled, for example, by the control unit 30 in the insulation resistance value detection unit 15. Alternatively, the first switch 11 may be controlled by an arbitrary control unit (not shown) consisting of a calculation processing device provided outside the insulation resistance value detection unit 15. The first switch 11 is, for example, an electromagnetic contactor. The closed state of the electric path from the AC power source 2 to the rectifier circuit 21 in the power source unit 12 is realized by closing the contacts of the first switch 11 which is an electromagnetic contactor, and the open state of the electric path from the AC power source 2 to the rectifier circuit 21 in the power source unit 12 is realized by opening the contacts of the first switch 11 which is an electromagnetic contactor. Note that the first switch 11 may be, for example, a relay or a semiconductor switching element instead of an electromagnetic contactor, as long as it can open and close the electric path from the AC power source 2.

[0019] The power supply unit 12 and the motor drive amplifier unit 13 are connected via a DC link. The "DC link" refers to a circuit portion that electrically connects the DC output side of the power supply unit 12 and the DC input side of the motor drive amplifier unit 13, and may also be called a "DC link unit," "DC link," "DC link unit," or "DC intermediate circuit."

[0020] The power supply unit 12 has a rectifier circuit 21 and a capacitor 22, and rectifies the AC voltage supplied from the AC power supply 2 via the first switch 11 in an open state into a DC voltage by the rectifier circuit 21, and smoothes the rectified DC voltage by the capacitor 22 before outputting it.

[0021] The rectifier circuit 21 in the power supply unit 12 may be any circuit capable of converting AC voltage into DC voltage, and may be, for example, a diode rectifier circuit, a 120-degree conduction type rectifier circuit, or a PWM switching control type rectifier circuit having a switching element therein. The rectifier circuit 21 is configured as a three-phase bridge circuit when the AC power source 2 is a three-phase AC power source, and is configured as a single-phase bridge circuit when the AC power source 2 is a single-phase AC power source. When the rectifier circuit 21 is a PWM switching control type rectifier circuit, it is made up of a bridge circuit of a switching element and a diode connected in reverse parallel thereto. In this case, examples of the switching element include an IGBT, a thyristor, a GTO (gate turn-off thyristor), a transistor, and the like, but the type of the switching element itself does not limit this embodiment, and other switching elements may be used.

[0022] The capacitor 22 in the power supply unit 12 has a function of smoothing the DC voltage output by the rectifier circuit 21 and a function of storing DC power in the DC link. The capacitor 22 may also be called a smoothing capacitor or a DC link capacitor. Examples of the capacitor 22 include an electrolytic capacitor and a film capacitor.

[0023] A first voltage measuring unit 14 is connected to both pole terminals of the capacitor 22. The first voltage measuring unit 14 is a measurement circuit that acquires a measured value of the (DC) voltage of the power supply unit 12, which is the voltage applied to the capacitor 22.

[0024] The motor drive amplifier unit 13 has an inverter configured with a bridge circuit in which a pair of switching elements and diodes connected in anti-parallel to the switching elements are provided on the upper and lower arms. In the illustrated example, the motor 3 is a three-phase AC motor, so the inverter in the motor drive amplifier unit 13 is configured with a three-phase bridge circuit. The switching element of the upper arm of the U phase is S u1 , the switching element of the lower arm of U phase is S u2 , the switching element of the upper arm of the V phase is S v1 , the switching element of the lower arm of the V phase is Sv2 , the upper arm switching element of the W phase is S w1 , the switching element of the lower arm of the W phase is S w2 Let us assume that.

[0025] The motor drive amplifier unit 13 performs power conversion operation by controlling the on / off operation of the switching elements of the upper arm and the lower arm by a PWM switching command from a higher-level control device (not shown). That is, the motor drive amplifier unit 13 converts a DC voltage in a DC link into an AC voltage for driving the motor and supplies it to the motor 3 by turning on and off the switching elements of the upper arm and the lower arm, and also converts the AC voltage regenerated by the motor 3 into a DC voltage and returns it to the DC link side during motor regeneration. In one embodiment of the present disclosure, the on / off operation of the switching elements of the upper arm and the lower arm in the motor drive amplifier unit 13 is also controlled by a control unit 30 of the insulation resistance value detection unit 15, the details of which will be described later.

[0026] The insulation resistance value detection unit 15 detects an insulation resistance value Rm [Ω] which is a resistance value of the insulation resistance 4 between the motor coil (winding) of the motor 3 and the ground. The insulation resistance value detection unit 15 has a control unit 30, a second switch 31, a measurement resistor 32, a second voltage measurement unit 33, a calculation unit 34, a correction value generation unit 35, and a correction unit 36. The detection of the insulation resistance value Rm [Ω] of the insulation resistance 4 of the motor 3 by the insulation resistance value detection unit 15 is performed using various data obtained regarding a first closed circuit obtained by opening the first switch 11 and closing the second switch 31, and turning off all switching elements in the motor drive amplifier unit 13. The first closed circuit is an insulation resistance value detection closed circuit including the second switch 31, the capacitor 22, the measurement resistor 32, the motor coil of the motor 3, and the ground.

[0027] The second switch 31 in the insulation resistance value detection unit 15 has one terminal connected to a voltage dividing resistor 38 and the other terminal connected to a voltage dividing resistor 39. The voltage dividing resistor 38 has one terminal connected to a positive power line connecting the rectifier circuit 21 and the capacitor 22 in the power supply unit 12. The voltage dividing resistor 39 has one terminal connected to the ground. The second switch 31 is controlled to be grounded by opening and closing it, that is, when in a closed state, the positive terminal of the capacitor 22 is connected to the ground, and when in an open state, one end of the capacitor is not connected to the ground. The opening and closing of the second switch 31 is controlled by the control unit 30. The second switch 31 is composed of, for example, a relay, a semiconductor switching element, or an electromagnetic contactor.

[0028] The measurement resistor 32 is provided between the negative terminal of the capacitor 22 and the motor coil of the motor 3. More specifically, one terminal of the measurement resistor 32 is connected to the negative terminal of the capacitor 22 via the negative power line of the motor drive amplifier unit 13. The other terminal of the measurement resistor 32 is connected to one phase of power lines connecting the motor drive amplifier unit 13 and the motor coil of the motor 3 via a voltage dividing resistor 37. In the illustrated example, as an example, the other terminal of the measurement resistor 32 is connected to a U-phase power line connecting the motor drive amplifier unit 13 and the U-phase motor coil of the motor 3. The second voltage measuring unit 33 is a measurement circuit that acquires a measured value of the terminal voltage of the measurement resistor 32. For example, the second voltage measuring unit 33 may be configured by an isolation amplifier consisting of the measurement resistor 32, the second voltage measuring unit 33, and a voltage dividing resistor 37. The voltage dividing resistor 37 is provided to adjust the input voltage to the isolation amplifier so as to fall within an appropriate range.

[0029] The correction value generating unit 35 generates a correction value based on the error detected by the error detecting unit 17 used when the fault determining unit 18 described later determines that the insulation resistance value detecting unit 15 has no fault.

[0030] The correction unit 36 ​​corrects the measurement value of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit is configured, using the correction value generated by the correction value generation unit 35, to generate a corrected measurement value of the terminal voltage of the measurement resistor 32. The corrected measurement value of the terminal voltage of the measurement resistor 32 generated by the correction unit 36 ​​is used by the calculation unit 34 to calculate the insulation resistance value Rm [Ω] of the motor 3.

[0031] When a first closed circuit is formed including the second switch 31, the capacitor 22, the measurement resistor 32, the motor coil of the motor 3, and the ground, the calculation unit 34 calculates the insulation resistance value Rm [Ω] of the insulation resistor 4 of the motor 3 based on the measured value of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14, the corrected measured value of the inter-terminal voltage of the measurement resistor 32 generated by the correction unit 36, and the resistance value of the measurement resistor 32. Details of the calculation process of the insulation resistance value by the calculation unit 34 will be described later.

[0032] The insulation resistance value of the motor 3 detected by the insulation resistance value detection unit 15 is sent to a display unit (not shown), and the display unit displays the "insulation resistance value of the motor 3" to notify an operator. Examples of the display unit include a standalone display device, a display device attached to the motor drive device 1, a display device attached to a higher-level control device (not shown), and a display device attached to a personal computer and a mobile terminal. For example, the insulation resistance value of the motor 3 detected by the insulation resistance value detection unit 15 is sent to an alarm output unit (not shown), and the alarm output unit may output an insulation resistance deterioration alarm when the insulation resistance value of the motor 3 falls below a predetermined value. The insulation resistance deterioration alarm output from the alarm output unit is sent to a light-emitting device (not shown), such as an LED or lamp, and the light-emitting device emits light when it receives the insulation resistance deterioration alarm to notify an operator of the "deterioration of the insulation resistance 4 of the motor 3." Also, for example, the insulation resistance degradation alarm output from the alarm output unit is sent to, for example, an audio device (not shown), and when the audio device receives the insulation resistance degradation alarm, it emits a sound such as a voice, speaker, buzzer, or chime to notify the worker of "deterioration of the insulation resistance 4 of the motor 3." This allows the worker to reliably and easily grasp the insulation resistance value of the motor 3 and the deterioration of the insulation resistance 4 of the motor 3, and can easily take measures such as replacing the motor 3 or disassembling and cleaning the motor 3.

[0033] The presence or absence of a failure in the insulation resistance value detection unit 15 is determined using various data obtained regarding the second closed circuit obtained by opening the first switch 11 and the second switch 31 and arbitrarily switching the switching elements of the upper arm or the lower arm of the motor drive amplifier unit 13. The second closed circuit is a failure determination closed circuit including the capacitor 22 and the measurement resistor 32.

[0034] The voltage estimation unit 16 calculates an estimate of the terminal-to-terminal voltage of the measurement resistor 32 based on the measured value of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 and the resistance value of the measurement resistor 32, in accordance with a circuit equation for a second closed circuit including the capacitor 22 and the measurement resistor 32, which is obtained by opening the first switch 11 and the second switch 31 and arbitrarily switching the switching elements of the upper arm or lower arm of the motor drive amplifier unit 13.

[0035] The error detection unit 17 detects the error between the measured value of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the second closed circuit is configured and the estimated value of the terminal voltage of the measurement resistor 32 calculated by the voltage estimation unit 16. The error detected by the error detection unit 17 is used in the failure determination process by the failure determination unit 18 and the correction value generation process by the correction value generation unit 35. It should be noted that the "measured value of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33" used in the error detection process by the error detection unit 17 is not the value corrected by the correction unit 36.

[0036] The fault determination unit 18 determines whether or not there is a fault in the insulation resistance value detection unit 15, based on the error detected by the error detection unit 17. More specifically, the fault determination unit 18 determines that there is a fault in the insulation resistance value detection unit 15 when the error detected by the error detection unit 17 is outside a predetermined range of a reference error, and determines that there is no fault in the insulation resistance value detection unit 15 when the error detected by the error detection unit 17 is within the range of the reference error.

[0037] The result of the determination by the failure determination unit 18 is used in the correction value generation process by the correction value generation unit 35.

[0038] As an option, the result of the determination by the failure determination unit 18 may be sent to a display unit (not shown). In this case, the display unit displays a message to inform the operator of "whether or not the insulation resistance value detection unit 15 is broken." Examples of the display unit include a standalone display device, a display device attached to the motor drive device 1, a display device attached to a higher-level control device (not shown), and a display device attached to a personal computer or a mobile terminal. For example, the result of the determination that the insulation resistance value detection unit 15 is broken may be sent to an alarm output unit (not shown), and the alarm output unit may output a failure detection alarm when it receives the result of the determination that the insulation resistance value detection unit 15 is broken. The failure detection alarm output from the alarm output unit is sent to a light-emitting device (not shown), such as an LED or a lamp, and the light-emitting device emits light when it receives the failure detection alarm, thereby notifying the operator of "failure of the insulation resistance value detection unit 15." Also, for example, the fault detection alarm output from the alarm output unit is sent to, for example, an audio device (not shown), and when the audio device receives the fault detection alarm, it emits a sound such as a voice, speaker, buzzer, or chime to notify the worker of the "fault in the insulation resistance value detection unit 15." This allows the worker to reliably and easily grasp the fault in the insulation resistance value detection unit 15, and also allows the worker to easily take measures such as replacing the insulation resistance value detection unit 15.

[0039] An arithmetic processing device (processor) is provided in the motor drive device 1. Examples of the arithmetic processing device include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing device has a first voltage measurement unit 14, a control unit 30, a second voltage measurement unit 33, a calculation unit 34, a correction value generation unit 35, a correction unit 36, a voltage estimation unit 16, an error detection unit 17, and a fault determination unit 18. Each of these units in the arithmetic processing device is a functional module realized by, for example, a computer program executed on the processor. For example, when the first voltage measurement unit 14, the control unit 30, the second voltage measurement unit 33, the calculation unit 34, the correction value generation unit 35, the correction unit 36, the voltage estimation unit 16, the error detection unit 17, and the fault determination unit 18 are constructed in the form of a computer program, the functions of each unit can be realized by operating the arithmetic processing device according to the computer program. Computer programs for executing the processes of the first voltage measurement unit 14, the control unit 30, the second voltage measurement unit 33, the calculation unit 34, the correction value generation unit 35, the correction unit 36, the voltage estimation unit 16, the error detection unit 17, and the fault determination unit 18 may be provided in a form recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the first voltage measurement unit 14, the control unit 30, the second voltage measurement unit 33, the calculation unit 34, the correction value generation unit 35, the correction unit 36, the voltage estimation unit 16, the error detection unit 17, and the fault determination unit 18 may be realized as a semiconductor integrated circuit in which a computer program for realizing the functions of each unit is written.

[0040] Next, the determination of the presence or absence of a failure in the insulation resistance value detection unit 15 will be described in more detail.

[0041] 2 is a diagram illustrating a second closed circuit configured when executing a process for determining whether or not an insulation resistance value detector has a failure in a motor drive device according to an embodiment of the present disclosure. In FIG. 2, the control unit 30, the calculation unit 34, the correction value generation unit 35, the correction unit 36, the voltage estimation unit 16, the error detection unit 17, and the failure determination unit 18 are not shown.

[0042] When executing the process of determining whether or not the insulation resistance value detection unit 15 has a failure, first, the first switch 11 is closed, the second switch 31 is open, and all switching elements in the motor drive amplifier unit 13 are turned off to charge the capacitor 22 with the power flowing from the AC power source 2 via the rectifier circuit 21. When the charging of the capacitor 22 is completed, the first switch 11 and the second switch 31 are opened and the switching elements of the upper arm or the lower arm of the motor drive amplifier unit 13 are switched on and off as desired to form a second closed circuit 102 indicated by a thick arrow in the figure. Note that the capacitor 22 is sufficiently charged even in a state in which the motor drive device 1 has already driven the motor 3 and then stopped driving the motor 3, so that in this state, the first switch 11 and the second switch 31 may be opened and the switching elements of the upper arm or the lower arm of the motor drive amplifier unit 13 may be switched on and off as desired to form the second closed circuit 102. In the illustrated example, as an example, the switching element S u1 is turned on, and other switching elements S u2 , S v1 , S v2 , S w1 , and S w2 As a result, the capacitor 22 and the switching element S u1 A second closed circuit 102 is formed including the voltage dividing resistor 37 and the measuring resistor 32.

[0043] The terminal voltage of the measurement resistor 32 can be estimated by using the measured value of the voltage of the power supply unit 12 (the voltage of the capacitor 22) acquired by the first voltage measurement unit 14 when the second closed circuit 102 is configured. When the resistance value of the measurement resistor 32 is Rb [Ω], the resistance value of the voltage dividing resistor 37 is Ra [Ω], and the measured value of the voltage of the power supply unit 12 (the voltage of the capacitor 22) acquired by the first voltage measurement unit 14 when the second closed circuit 102 is configured is Vdc [V], the estimated value Vin1 [V] of the terminal voltage of the measurement resistor 32 can be calculated based on Equation 1. Note that the second closed circuit 102 also includes the on-resistance of a switching element (e.g., IGBT) in the motor drive amplifier unit 13, but since the value is very small, the on-resistance of the switching element is ignored in Equation 1 and the following equations.

[0044]

number

[0045] The voltage estimation unit 16 calculates an estimated value Vin1 [V] of the voltage between the terminals of the measurement resistor 32 based on the measured value Vdc [V] of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 when the second closed circuit 102 is configured, the resistance value Rb [Ω] of the measurement resistor 32, and the resistance value Ra [Ω] of the voltage dividing resistor 37, based on Equation 1. The resistance value Rb [Ω] of the measurement resistor 32 and the resistance value Ra [Ω] of the voltage dividing resistor 37 are known, and for example, the nominal values ​​of the manufacturers of these components may be used. The resistance value Rb [Ω] of the measurement resistor 32 and the resistance value Ra [Ω] of the voltage dividing resistor 37 may be input in advance into the arithmetic processing device constituting the voltage estimation unit 16 and used in the calculation of the estimated value Vin1 [V] of the voltage between the terminals of the measurement resistor 32 by the voltage estimation unit 16.

[0046] On the other hand, when the second closed circuit 102 is similarly configured, the second voltage measuring unit 33 can also obtain the measured value (actual measured value) Vin2 [V] of the inter-terminal voltage of the measuring resistor 32.

[0047] When the second closed circuit 102 is configured, the estimated value Vin1 [V] of the terminal voltage of the measurement resistor 32 and the measured value (actual value) Vin2 [V] of the terminal voltage of the measurement resistor 32 are ideally equal. However, in reality, there is an error between the two due to component errors and aging of the second voltage measurement unit 33, the measurement resistor 32, and the voltage dividing resistor 37 that configure the isolation amplifier. The error ΔV [V] between the estimated value Vin1 [V] of the terminal voltage of the measurement resistor 32 and the measured value (actual value) Vin2 [V] of the terminal voltage of the measurement resistor 32 is expressed as in Equation 2.

[0048]

number

[0049] The error detection unit 17 detects an error ΔV [V] between the measured value Vin2 [V] of the inter-terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the second closed circuit 102 is configured and the estimated value Vin1 [V] of the inter-terminal voltage of the measurement resistor 32 calculated by the voltage estimation unit 16, based on Equation 2. The error ΔV [V] detected by the error detection unit 17 is used in the fault determination process by the fault determination unit 18.

[0050] If the error ΔV [V] detected by the error detection unit 17 is outside a predetermined range of a reference error, the failure determination unit 18 determines that there is a failure in the insulation resistance value detection unit 15, and if the error ΔV [V] detected by the error detection unit 17 is within the range of the reference error, it determines that there is no failure in the insulation resistance value detection unit 15. If the lower limit of the range of the reference error is, for example, Vth1 [V] and the upper limit is, for example, Vth2 [V], then Equation 3 used in the failure determination process by the failure determination unit 18 is obtained.

[0051]

number

[0052] The failure determination unit 18 determines whether or not the insulation resistance value detection unit 15 has a failure based on the error detected by the error detection unit 17, for example, using Equation 3.

[0053] Note that the lower limit value Vth1 [V] and the upper limit value Vth2 [V] of the range of the reference error used in the failure determination process by the failure determination unit 18 have the relationship of "Vth1 <Vth2", and each can take positive and negative values. Regarding the lower limit value Vth1 [V] and the upper limit value Vth2 [V] of the range of the reference error, for example, by operating the motor drive device 1 through experiments or actual operations, or by computer simulation, the application environment of the isolation amplifier including the second voltage measurement unit 33, the application environment of the motor drive device 1, and the relationship with the presence or absence of the output of the alarm signal in the motor drive device 1, etc. can be obtained in advance and then set as appropriate. Regarding the lower limit value Vth1 [V] and the upper limit value Vth2 [V] of the range of the reference error, they may be stored in a rewritable storage unit (not shown) and can be rewritten by an external device. According to this, even after the lower limit value Vth1 [V] and the upper limit value Vth2 [V] of the range of the reference error are once set, they can be changed to appropriate values as needed. The storage unit for storing the lower limit value Vth1 [V] and the upper limit value Vth2 [V] of the range of the reference error may be composed of, for example, an electrically erasable and recordable non-volatile memory such as EEPROM (registered trademark), or a random access memory such as DRAM or SRAM that can be read and written at high speed. Regarding the set lower limit value Vth1 [V] and upper limit value Vth2 [V] of the range of the reference error, they may be input in advance into the arithmetic processing unit constituting the failure determination unit 18 and used in the failure determination process by the failure determination unit 18.

[0054] FIG. 3 is a flowchart showing the operation flow of the determination process of the presence or absence of a failure of the insulation resistance value detection unit in the motor drive device according to an embodiment of the present disclosure.

[0055] In step S101, the control unit 30 controls the first switch 11 to a closed state and the second switch 31 to an open state. The control unit 30 also controls all switching elements in the motor drive amplifier unit 13 to an off state. As a result, in step S102, the capacitor 22 is charged with power flowing from the AC power source 2 via the rectifier circuit 21. The charge state of the capacitor 22 is monitored by the control unit 30 via the first voltage measurement unit 14. Note that in a state in which the motor 3 has already been driven by the motor drive device 1 and the drive of the motor 3 is then stopped, the capacitor 22 is sufficiently charged, and in this case, step S102 may be omitted.

[0056] When charging of the capacitor 22 is completed, in step S103, the control unit 30 switches the first switch 11 from a closed state to an open state, thereby setting the first switch 11 and the second switch 31 to an open state. In addition, the control unit 30 arbitrarily switches on or off the switching element of the upper arm or the lower arm of the motor drive amplifier unit 13. In the example shown in FIG. 2, as an example, the switching element S of the upper arm of the U phase of the motor drive amplifier unit 13 is u1 is turned on, and other switching elements S u2 , S v1 , S v2 , S w1 , and S w2 As a result, the capacitor 22 and the switching element S u1 A second closed circuit 102 is formed including the voltage dividing resistor 37 and the measuring resistor 32.

[0057] In step S104, the first voltage measuring unit 14 obtains a measurement value of the voltage of the power supply unit 12 (the voltage of the capacitor 22).

[0058] In step S105, the voltage estimation unit 16 calculates, based on Equation 1, an estimate value Vin1 [V] of the inter-terminal voltage of the measurement resistor 32 based on the measured value Vdc [V] of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 when the second closed circuit 102 is configured, the resistance value Rb [Ω] of the measurement resistor 32, and the resistance value Ra [Ω] of the voltage dividing resistor 37.

[0059] In step S106, the second voltage measuring unit 33 acquires a measured value Vin2 [V] of the inter-terminal voltage of the measuring resistor 32 when the second closed circuit 102 is configured.

[0060] The order of steps S104 to S106 may be changed as appropriate within the scope of no contradiction. For example, steps S104 and S105 may be executed after step S106, or step S106 may be executed between steps S104 and S105. However, step S105 should be executed at least after S104.

[0061] In step S107, the error detection unit 17 detects, based on Equation 2, the error ΔV [V] between the measurement value Vin2 [V] of the inter-terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the second closed circuit 102 is constructed, and the estimated value Vin1 [V] of the inter-terminal voltage of the measurement resistor 32 calculated by the voltage estimation unit 16.

[0062] In step S108, the fault determination unit 18 determines whether or not the error ΔV [V] detected by the error detection unit 17 is outside the range of a predefined reference error. If it is determined in step S108 that the error ΔV [V] is outside the range of the reference error, the process proceeds to step S109, where the fault determination unit 18 determines that there is a fault in the insulation resistance value detection unit 15. If it is not determined in step S108 that the error ΔV [V] is outside the range of the reference error (i.e., the error ΔV [V] is within the range of the reference error), the process proceeds to step S110, where the fault determination unit 18 determines that there is no fault in the insulation resistance value detection unit 15.

[0063] Next, detection of the insulation resistance value Rm [Ω] of the insulation resistor 4 of the motor 3 by the insulation resistance value detection unit 15 will be described in more detail.

[0064] 4 is a diagram illustrating a first closed circuit configured when an insulation resistance value detection process is executed by an insulation resistance value detection unit in a motor drive device according to an embodiment of the present disclosure. In FIG. 4, the control unit 30, the calculation unit 34, the correction value generation unit 35, the correction unit 36, the voltage estimation unit 16, the error detection unit 17, and the fault determination unit 18 are not shown.

[0065] When the insulation resistance value detection process is performed by the insulation resistance value detection unit 15, first, the first switch 11 is closed, the second switch 31 is open, and all switching elements in the motor drive amplifier unit 13 are turned off, and the capacitor 22 is charged with power flowing from the AC power source 2 through the rectifier circuit 21. When the charging of the capacitor 22 is completed, the first switch 11 is opened, the second switch 31 is closed, and all switching elements of the upper arm and lower arm of the motor drive amplifier unit 13 are turned off, thereby forming a first closed circuit 101 indicated by a thick arrow in the figure. FIG. 7 is a circuit diagram showing a portion related to the first closed circuit. In FIG. 7, the second switch 31 in the closed state is omitted from the illustration. As shown in Figures 4 and 7, the first closed circuit 101 includes a capacitor 22, a voltage dividing resistor 38, a second switch 31 in a closed state, a voltage dividing resistor 39, an insulation resistor 4 of the motor coil of the motor 3, a voltage dividing resistor 37, and a measurement resistor 32.

[0066] In a state where the first closed circuit 101 is configured, the leakage current I flowing through the first closed circuit 101 is calculated according to Equation 4 from the measured value (actual value) Vin3 [V] of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 and the resistance value Rb [Ω] of the measurement resistor 32. 1 [A] can be calculated.

[0067]

number

[0068] In a state where the first closed circuit 101 is configured, the measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) acquired by the first voltage measurement unit 14 and the leakage current I flowing through the first closed circuit 101 are 1 The circuit equation expressed by Equation 5 is established from [A], the resistance value Rb [Ω] of measurement resistor 32, the resistance value Ra [Ω] of voltage dividing resistor 37, the resistance value Rc [Ω] of voltage dividing resistor 38, the resistance value Rd [Ω] of voltage dividing resistor 39, and the insulation resistance value Rm [Ω] of insulation resistor 4 of motor 3.

[0069]

number

[0070] Substituting Equation 5 into Equation 4 and rearranging it gives Equation 6.

[0071]

number

[0072] According to the formula 6, the insulation resistance value Rm [Ω] of the insulation resistor 4 of the motor 3 can be calculated. However, the output of the second voltage measurement unit 33 includes an error ΔV due to component errors and aging of the second voltage measurement unit 33, the measurement resistor 32, and the voltage dividing resistor 37 that constitute the insulation amplifier. Therefore, a value "-ΔV [V]" obtained by inverting the polarity of the error ΔV [V] is used as a correction value Vamend [V] for correcting the measured value Vin3 [V] of the voltage between the terminals of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit 101 is constituted. Here, the error ΔV [V] used to create the correction value Vamend [V] is the error ΔV [V] used when it is determined that the error is within the range of the reference error, that is, when the failure determination unit 18 determines that there is no failure in the insulation resistance value detection unit 15. The correction value Vamend [V] is expressed as in Equation 7, using the error ΔV [V] used when the failure determination unit 18 determined that there was no failure in the insulation resistance value detection unit 15. Since the offset error is more dominant than the gain error in the error ΔV [V], in this embodiment, as shown in Equation 7 as an example, a correction value Vamend [V] for canceling the offset error is generated by adding (plusing) the error ΔV [V] to the measured value Vin3 [V] of the inter-terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit 101 is configured.

[0073]

number

[0074] The correction value generating unit 35 generates the correction value Vamend [V] based on Equation 7, using the error ΔV [V] used when the failure determining unit 18 determined that the insulation resistance value detecting unit 15 had no failure.

[0075] By adding the correction value Vamend [V] to the measurement value Vin3 [V] of the inter-terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit 101 is constructed, the corrected measurement value Vin4 [V] of the inter-terminal voltage of the measurement resistor 32 is obtained as shown in Equation 8.

[0076]

number

[0077] Based on Equation 8, the correction unit 36 ​​corrects the measurement value Vin3 [V] of the inter-terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit 101 is constructed, using the correction value Vamend [V] generated by the correction value generation unit 35, thereby generating a corrected measurement value Vin4 [V] of the inter-terminal voltage of the measurement resistor 32.

[0078] The accuracy of the insulation resistance value Rm [Ω] is improved by calculating the insulation resistance value Rm [Ω] for the insulation resistance 4 of the motor 3 based on equation 9 obtained by replacing the measurement value Vin3 [V] of the terminal voltage of the measurement resistor 32 in equation 6 with the corrected measurement value Vin4 [V] of the terminal voltage of the measurement resistor 32.

[0079]

number

[0080] When the fault judgment unit 18 judges that there is no fault in the insulation resistance value detection unit 15, the calculation unit 34 calculates, based on Equation 9, the insulation resistance value Rm [Ω] for the insulation resistor 4 of the motor 3 based on the measured value Vdc [V] of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 when the first closed circuit 101 is constructed, the corrected measured value Vin4 [V] of the voltage between the terminals of the measurement resistor 32, and at least the resistance value Rb [Ω] of the measurement resistor 32. 1 and 4, when the failure determination unit 18 determines that the insulation resistance value detection unit 15 is not faulty, the calculation unit 34 calculates the insulation resistance value Rm [Ω] of the insulation resistance 4 of the motor 3 based on the measured value Vdc [V] of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 when the first closed circuit 101 is configured, the corrected measured value Vin4 [V] of the voltage between the terminals of the measurement resistor 32, the resistance value Rb [Ω] of the measurement resistor 32, the resistance value Ra [Ω] of the voltage dividing resistor 37, the resistance value Rc [Ω] of the voltage dividing resistor 38, and the resistance value Rd [Ω] of the voltage dividing resistor 39, based on Equation 9. On the other hand, when the failure determination unit 18 determines that the insulation resistance value detection unit 15 is not faulty, the calculation unit 34 does not execute the insulation resistance value detection process of the insulation resistance value detection unit 15 and ends the process.

[0081] FIG. 5 is a flowchart (part 1) showing the operation flow of the insulation resistance value detection process by the insulation resistance value detection unit in a motor drive device according to one embodiment of the present disclosure, and FIG. 6 is a flowchart (part 2) showing the operation flow of the insulation resistance value detection process by the insulation resistance value detection unit in a motor drive device according to one embodiment of the present disclosure.

[0082] Steps S101 to S110 shown in FIG. 5 are similar to the processes in steps S101 to S110 shown in FIG.

[0083] If it is not determined in step S108 that the error ΔV [V] is outside the range of the standard error (i.e., if the error ΔV [V] is within the range of the standard error), the process proceeds to step S110, and the fault determination unit 18 determines that there is no fault in the insulation resistance value detection unit 15.

[0084] In step S200 following step S110, the insulation resistance value detection unit 15 starts the insulation resistance value detection process.

[0085] Incidentally, since the capacitance of the capacitor 22 (for example, an electrolytic capacitor) is generally large, a leakage current flows only for a short time during the error calculation process from step S103 to S110, and therefore the amount of charge loss in the capacitor 22 is very small. Therefore, when executing the insulation resistance value calculation process from step S200 onwards, it is basically not necessary to recharge the capacitor 22, but the capacitor 22 may be recharged as necessary.

[0086] In step S201, the correction value generation unit 35 generates a correction value Vamend [V] based on Equation 7, using the error ΔV [V] used when the fault judgment unit 18 judged that there was no fault in the insulation resistance value detection unit 15.

[0087] In step S202, the control unit 30 switches the second switch 31 from an open state to a closed state. As a result, the first switch 11 is opened and the second switch 31 is closed. In addition, all switching elements of the upper arm and lower arm of the motor drive amplifier unit 13 are turned off. As a result, the first closed circuit 101 is formed.

[0088] In step S203, the first voltage measuring unit 14 obtains a measurement value of the voltage of the power supply unit 12 (the voltage of the capacitor 22).

[0089] In step S204, the second voltage measuring unit 33 acquires a measured value Vin3 [V] of the inter-terminal voltage of the measuring resistor 32 when the first closed circuit 101 is configured.

[0090] In step S205, the correction unit 36 ​​corrects the measurement value Vin3 [V] of the inter-terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit 101 is constructed, using the correction value Vamend [V] generated by the correction value generation unit 35, based on Equation 8, to generate a corrected measurement value Vin4 [V] of the inter-terminal voltage of the measurement resistor 32.

[0091] In step S206, if the fault judgment unit 18 judges that there is no fault in the insulation resistance value detection unit 15, the calculation unit 34 calculates, based on Equation 9, the insulation resistance value Rm [Ω] for the insulation resistor 4 of the motor 3 based on the measured value Vdc [V] of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 when the first closed circuit 101 is constructed, the corrected measured value Vin4 [V] of the voltage between the terminals of the measurement resistor 32, and at least the resistance value Rb [Ω] of the measurement resistor 32. More specifically, in the example shown in Figures 1 and 4, when the fault determination unit 18 determines that there is no fault in the insulation resistance value detection unit 15, the calculation unit 34 calculates, based on Equation 9, the insulation resistance value Rm [Ω] for the insulation resistor 4 of the motor 3 based on the measured value Vdc [V] of the voltage of the power supply unit 12 acquired by the first voltage measurement unit 14 when the first closed circuit 101 is configured, the corrected measured value Vin4 [V] of the voltage between the terminals of the measurement resistor 32, the resistance value Rb [Ω] of the measurement resistor 32, the resistance value Ra [Ω] of the voltage dividing resistor 37, the resistance value Rc [Ω] of the voltage dividing resistor 38, and the resistance value Rd [Ω] of the voltage dividing resistor 39.

[0092] Here, we will explain, using numerical examples, the effect that the error ΔV [V] caused by component errors and deterioration over time of the second voltage measurement unit 33, the measurement resistor 32, and the voltage dividing resistor 37 that constitute the insulation amplifier has on the detection accuracy of the insulation resistance value Rm [Ω] of the motor 3.

[0093] For example, consider a numerical example in which the resistance value Rc of voltage-dividing resistor 38 is 1000 kΩ, the resistance value Rd of voltage-dividing resistor 39 is 5 kΩ, the resistance value Rb of measurement resistor 32 is 5 kΩ, the resistance value Ra of voltage-dividing resistor 37 is 1000 kΩ, and the voltage Vdc of power supply unit 12 (voltage of capacitor 22) is 300 V.

[0094] If the actual insulation resistance value Rm of the motor 3 is 1 MΩ, the terminal voltage of the measurement resistor 32 is calculated to be 498 mV using Equation 6 based on the first closed circuit 101. If the measured value Vin3 of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33, which is 498 mV, contains an error ΔV of 10 mV, the correct measured value Vin3 of the terminal voltage of the measurement resistor 32 should be 488 mV. Therefore, if Vin3 = 488 mV is substituted into Equation 6 and the insulation resistance value Rm of the motor 3 is recalculated to be 1.06 MΩ, which is deviated from the actual insulation resistance value Rm = 1 MΩ of the motor 3.

[0095] If the actual insulation resistance value Rm of the motor 3 is 10 MΩ, the terminal voltage of the measurement resistor 32 is calculated to be 125 mV using Equation 6 based on the first closed circuit 101. If the measured value Vin3 of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33, which is 125 mV, contains an error ΔV of 10 mV, the correct measured value Vin3 of the terminal voltage of the measurement resistor 32 should be 115 mV. Therefore, if Vin3 = 115 mV is substituted into Equation 6 and the insulation resistance value Rm of the motor 3 is recalculated to be 11.03 MΩ, which is deviated from the actual insulation resistance value Rm of the motor 3, which is 10 MΩ.

[0096] If the actual insulation resistance value Rm of the motor 3 is 50 MΩ, the terminal voltage of the measurement resistor 32 is calculated to be 29 mV using Equation 6 based on the first closed circuit 101. If the measured value Vin3 of the terminal voltage of the measurement resistor 32 acquired by the second voltage measurement unit 33, which is 29 mV, contains an error ΔV of 10 mV, the correct measured value Vin3 of the terminal voltage of the measurement resistor 32 should be 19 mV. Therefore, if Vin3=19 mV is substituted into Equation 6 and the insulation resistance value Rm of the motor 3 is recalculated, the value becomes 76.94 MΩ, which is deviated from the actual insulation resistance value Rm=50 MΩ of the motor 3.

[0097] As shown by the above-mentioned numerical example, the larger the actual insulation resistance value Rm [Ω] of the motor 3, the larger the error will be when the insulation resistance value of the motor 3 is calculated while the error ΔV is still included in the measured value Vin3 of the voltage between the terminals of the measurement resistor 32 acquired by the second voltage measurement unit 33 when the first closed circuit 101 is configured. According to this embodiment, the measured value Vin3 [V] of the voltage between the terminals of the measurement resistor 32 acquired by the second voltage measurement unit 33 is corrected using the value "-ΔV [V]" obtained by inverting the polarity of the error ΔV [V] as the correction value Vamend [V], and the insulation resistance value Rm [Ω] is calculated using the corrected measured value Vin4 [V] of the voltage between the terminals of the measurement resistor 32, so that the insulation resistance value Rm [Ω] of the motor 3 can be accurately detected.

[0098] As described above, according to the motor drive device 1 according to an embodiment of the present disclosure, the failure determination process is performed based on the error ΔV [V] caused by component errors and aging of the second voltage measurement unit 33, the measurement resistor 32, and the voltage dividing resistor 37, so that it is possible to accurately detect a failure in the insulation resistance value detection unit 15 that detects the insulation resistance value of the motor 3. In addition, the measurement value Vin3 [V] of the measurement resistor 32 measured by the second voltage measurement unit 33 is corrected using the error ΔV [V] used when the failure determination unit 18 determines that there is no failure in the insulation resistance value detection unit 15, and the insulation resistance value Rm [Ω] of the motor 3 is calculated based on the corrected measurement value Vin4 [V] of the measurement resistor 32, so that it is possible to accurately detect the insulation resistance value Rm [Ω] of the motor 3.

[0099] Next, a modified example of the motor drive device 1 according to an embodiment of the present disclosure will be described.

[0100] FIG. 8 is a diagram illustrating a modified example of a motor drive device according to an embodiment of the present disclosure.

[0101] In the first closed circuit 101 used in the insulation resistance value detection process of the insulation resistance value detection unit 15 shown in FIG. 4 and FIG. 7, the voltage (voltage of the capacitor 22) Vdc [V] of the power supply unit 12 is applied to a combined resistance obtained by the voltage dividing resistor 39, the insulation resistance 4 of the motor 3, the voltage dividing resistor 37, and the measurement resistor 32. Therefore, the leakage current I 1 [A] is very small. Therefore, the detection resolution of the second voltage measurement unit 33 is ensured by narrowing the input voltage range of the insulation amplifier consisting of the measurement resistor 32, the second voltage measurement unit 33, and the voltage dividing resistor 37. Meanwhile, in the second closed circuit 102 used in the process of determining whether or not there is a malfunction in the insulation resistance value detection unit 15 shown in FIG. 2, the voltage Vdc [V] of the power supply unit 12 (the voltage of the capacitor 22) is applied to a combined resistance obtained by the voltage dividing resistor 37 and the measurement resistor 32, so that the current flowing in the second closed circuit 102 is smaller than the leakage current I flowing in the first closed circuit 101. 1 [A]. For this reason, if an insulating amplifier with a small input voltage range is used in order to ensure the detection resolution of the second voltage measurement unit 33, the voltage applied to the measurement resistor 32 during the process of determining whether or not the insulation resistance value detection unit 15 has a malfunction may deviate from the input voltage range of the insulating amplifier, making it impossible to accurately determine whether or not the insulation resistance value detection unit 15 has a malfunction. Conversely, if an insulating amplifier with a large input voltage range is used in order to accurately determine whether or not the insulation resistance value detection unit 15 has a malfunction, the detection resolution of the second voltage measurement unit 33 will decrease.

[0102] In order to solve such a problem, in a modified example of the motor drive device according to an embodiment of the present disclosure, before executing a process for determining whether or not the insulation resistance value detection unit 15 has a failure, the first switch 11 and the second switch 31 are opened, and all switching elements of the upper arm and the lower arm of the motor drive amplifier unit 13 are turned off, thereby forming a discharge circuit consisting of the capacitor 22 and the first voltage measurement unit 14. The first voltage measurement unit 14 is composed of, for example, a measurement resistor (not shown), a voltage dividing resistor (not shown), and an insulation amplifier, and by forming the discharge circuit, the charge of the capacitor 22 can be discharged through the measurement resistor (not shown) and the voltage dividing resistor (not shown) in the first voltage measurement unit 14. Then, after the voltage Vdc [V] of the power supply unit 12 (the voltage of the capacitor 22) becomes equal to or lower than a predetermined reference voltage due to the discharge, the second closed circuit 102 is formed again, and the second voltage measurement unit is caused to obtain a measured value Vin2 [V] of the voltage between the terminals of the measurement resistor 32.

[0103] The motor drive device 1 according to this modification further includes a voltage determination unit 19. The voltage determination unit 19 determines whether or not a measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) acquired by the first voltage measurement unit 14 when the first switch 11 and the second switch 31 are in an open state and all switching elements of the upper arm and the lower arm of the motor drive amplifier unit 13 are in an off state becomes equal to or lower than a predetermined reference voltage Vth3 [V]. The voltage determination unit 19 is configured in a calculation processing device, and is a functional module realized by, for example, a computer program executed on a processor. For example, when the voltage determination unit 19 is constructed in a computer program format, the function of the voltage determination unit 19 can be realized by operating the calculation processing device according to the computer program. The computer program for executing the processing of the voltage determination unit 19 may be provided in a form recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the voltage determination unit 19 may be realized as a semiconductor integrated circuit in which a computer program for realizing the function is written.

[0104] When the first switch 11 and the second switch 31 are opened and all switching elements of the upper arm and lower arm of the motor drive amplifier unit 13 are turned off, after the voltage judgment unit 19 has determined that the measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) acquired by the first voltage measurement unit 14 has become equal to or lower than the reference value Vth3 [V], the second closed circuit 102 is re-configured and the second voltage measurement unit 33 acquires the measured value of the voltage between the terminals of the measurement resistor 32.

[0105] The reference voltage Vth3 [V] used in the voltage determination process by the voltage determination unit 19 may be set according to an insulating amplifier having an input voltage range that can ensure the desired detection resolution of the second voltage measurement unit 33. The reference voltage Vth3 [V] may be stored in a rewritable storage unit (not shown) and rewritable by an external device, and even after the reference voltage Vth3 [V] is once set, it can be changed to an appropriate value as necessary. The storage unit that stores the reference voltage Vth3 [V] may be composed of an electrically erasable and recordable non-volatile memory such as an EEPROM (registered trademark), or a high-speed readable and writable random access memory such as a DRAM or SRAM. The set reference voltage Vth3 [V] may be input in advance into the arithmetic processing device that constitutes the voltage determination unit 19 and used in the voltage determination process by the voltage determination unit 19.

[0106] An example of the numerical value of the reference voltage Vth3 [V] is as follows. For example, assume that the resistance value Rb of the measurement resistor 32 is 5 kΩ, the resistance value Ra of the voltage dividing resistor 37 is 1000 kΩ, and the input voltage range of the second voltage measuring unit 33 in the isolation amplifier is, for example, from 0 mV to 1000 mV. In this example, when the voltage (voltage of the capacitor 22) Vdc of the power supply unit 12 is 300 V, the terminal voltage Vin2 of the measurement resistor 32 when the second closed circuit 102 is formed is calculated according to Ohm's law to be about 1493 mV, which exceeds the upper limit of the input voltage range of the second voltage measuring unit 33. In order to keep the terminal voltage Vin2 [V] of the measurement resistor 32 below the upper limit of the input voltage range of the second voltage measuring unit 33, which is 1000 mV, the voltage Vdc of the power supply unit 12 (voltage of the capacitor 22) needs to be reduced to about 200 V. Therefore, the voltage determination unit 19 may be configured such that the reference voltage Vth3 is set to, for example, 200 V. Note that the numerical examples given here are merely examples.

[0107] The configuration of motor drive device 1 according to this modification, other than voltage determination unit 19 and second voltage measurement unit 33, is as described with reference to FIG.

[0108] FIG. 9 is a flowchart showing an operation flow of a process for determining whether or not there is a malfunction in the insulation resistance value detector in the motor drive device according to the modified example of the embodiment of the present disclosure.

[0109] Steps S101 and S102 shown in FIG. 9 are the same as the processes of steps S101 and S102 shown in FIG. 1 and FIG. 3. After the charging of the capacitor 22 is completed in step S102, the control unit 30 switches the first switch 11 from a closed state to an open state in step S103 to control the first switch 11 and the second switch 31 to an open state, and controls all switching elements of the upper arm and the lower arm of the motor drive amplifier unit 13 to an off state, thereby forming a discharge circuit consisting of the capacitor 22 and the first voltage measurement unit 14. By forming the discharge circuit, the capacitor 22 is gradually discharged by a measurement resistor (not shown) and a voltage dividing resistor (not shown) in the first voltage measurement unit 14. In step S104, the first voltage measurement unit 14 acquires a measured value of the voltage of the power supply unit 12 (the voltage of the capacitor 22).

[0110] In step S111 following step S104, the voltage determination unit 19 determines whether or not the measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) acquired by the first voltage measurement unit 14 has become equal to or less than the predetermined reference voltage Vth3 [V]. If it is determined in step S111 that the measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) has not become equal to or less than the reference voltage Vth3 [V], the process returns to step S104. If it is determined in step S111 that the measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) has become equal to or less than the reference voltage Vth3 [V], the process proceeds to step S105 after forming the second closed circuit 102 by arbitrarily switching the switching element in the motor drive amplifier unit 13. Steps S104 and S111 are repeatedly executed until the capacitor 22 is discharged and the measured value Vdc [V] of the voltage of the power supply unit 12 (the voltage of the capacitor 22) becomes equal to or lower than the reference voltage Vth3 [V].

[0111] Steps S105 to S110 and S200 shown in Fig. 9 are similar to the processes of steps S105 to S110 and S200 shown in Fig. 3. After the process of step S200 shown in Fig. 9, steps S201 to S206 shown in Fig. 6 are further executed.

[0112] As described above, according to the modified example of the motor drive device 1 according to an embodiment of the present disclosure, the detection resolution of the second voltage measurement unit 33 can be effectively ensured, so that a fault in the circuit of the insulation resistance value detection unit 15 that detects the insulation resistance value of the motor 3 can be accurately detected, and the insulation resistance value Rm [Ω] of the motor 3 can be detected even more accurately. [Explanation of symbols]

[0113] 1 Motor drive unit 2 AC power supply 3 Motor 4. Insulation resistance 11 First Switch 12 Power supply section 13 Motor drive amplifier section 14 First voltage measuring unit 15 Insulation resistance detector 16 Voltage Estimation Unit 17 Error detection section 18 Failure determination section 19 Voltage judgment section 21 Rectifier circuit 22 Capacitor 30 Control section 31 Second Switch 32 Measuring resistance 33 Second voltage measurement section 34 Calculation section 35 Correction value generator 36 Correction section 37, 38, 39 Voltage divider resistor 101 First Closed Circuit 102 Second Closed Circuit

Claims

[Claim 1] a first switch for opening and closing an electric path from an AC power source; a power supply unit that rectifies an AC voltage supplied from the AC power supply through the first switch in a closed state into a DC voltage using a rectifier circuit and smoothes the rectified DC voltage using a capacitor; a motor drive amplifier unit that converts a DC voltage from the power supply unit into an AC voltage for driving a motor using upper and lower arm switching elements and supplies the AC voltage to the motor; a first voltage measurement unit that acquires a measurement value of the voltage of the power supply unit; a voltage determination unit that determines whether or not a measured value of the voltage of the power supply unit acquired by the first voltage measurement unit is equal to or lower than a predetermined reference voltage; an insulation resistance value detection unit having: a second switch that connects one end of the capacitor to the ground when in a closed state and does not connect one end of the capacitor to the ground when in an open state; a measurement resistor provided between the other end of the capacitor and a motor coil; a second voltage measurement unit that acquires a measured value of a voltage between the terminals of the measurement resistor; and a calculation unit that calculates an insulation resistance value of the motor based on the measured value of the voltage of the power supply unit acquired by the first voltage measurement unit, the measured value of the voltage between the terminals of the measurement resistor acquired by the second voltage measurement unit, and the resistance value of the measurement resistor when a first closed circuit including the second switch, the capacitor, the measurement resistor, the motor coil, and the ground is formed by opening the first switch and closing the second switch; a voltage estimation unit that calculates an estimate of a voltage between the terminals of the measurement resistor based on a measurement value of the voltage of the power supply unit acquired by the first voltage measurement unit and a resistance value of the measurement resistor when a second closed circuit including the capacitor and the measurement resistor is formed by opening the first switch and the second switch and arbitrarily switching the switching element of the upper arm or the lower arm of the motor drive amplifier unit; an error detection unit that detects an error between a measured value of the inter-terminal voltage of the measurement resistor acquired by the second voltage measurement unit when the second closed circuit is configured and an estimated value of the inter-terminal voltage of the measurement resistor calculated by the voltage estimation unit; a failure determination unit that determines whether or not the insulation resistance value detection unit has a failure based on the error detected by the error detection unit; Equipped with When the error detected by the error detection unit is outside a range of a predetermined reference error, it is determined that the insulation resistance value detection unit has a malfunction, and when the error detected by the error detection unit is within the range of the reference error, it is determined that the insulation resistance value detection unit has no malfunction, The insulation resistance value detection unit includes: a correction value generating unit that generates a correction value based on the error detected by the error detecting unit and used when the failure determining unit determines that the insulation resistance value detecting unit is not faulty; a correction unit that generates a corrected measurement value of the inter-terminal voltage of the measurement resistor by correcting the measurement value of the inter-terminal voltage of the measurement resistor obtained by the second voltage measurement unit when the first closed circuit is configured, using the correction value generated by the correction value generation unit; and and the calculation unit detects an insulation resistance value of the motor based on a measured value of the voltage of the power supply unit acquired by the first voltage measurement unit when the first closed circuit is configured, a corrected measured value of the voltage between the terminals of the measurement resistor, and a resistance value of the measurement resistor; The motor drive device, wherein the second voltage measurement unit acquires a measurement value of the voltage between the terminals of the measurement resistor when the second closed circuit is configured after the voltage determination unit determines that the measurement value of the voltage of the power supply unit acquired by the first voltage measurement unit has become equal to or lower than the reference voltage when the first switch and the second switch are opened and the switching elements of the upper arm and the lower arm of the motor drive amplifier unit are turned off.

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