JP7090829B1 - Motor control device - Google Patents

Abstract

The motor control device (1) includes a rectifying circuit (7), a switch (4) arranged between the AC power supply (2) and the rectifying circuit (7), and an inverter that supplies AC power to the motor (3). A control unit (10) that outputs a signal for controlling the continuity and non-conduction of the switching element of the circuit (8) and the inverter circuit (8) and outputs a signal for switching the continuity and non-conduction of the switch (4). A voltage generation circuit (31) that draws in the voltage of each phase wiring in the power supply voltage supply cable (5) that connects the AC power supply (2) and the switch (4) to generate an insulation resistance voltage according to the insulation resistance, and a voltage. A voltage detection circuit (32) for detecting the insulation resistance voltage generated in the generation circuit (31) is provided.

Description

The present disclosure relates to a motor control device that controls a motor mounted on an electric device.

In electrical equipment, dielectric breakdown in which the deterioration of the insulation performance of the electrical equipment exceeds a certain value may cause electric leakage and lead to a serious accident. Therefore, leakage due to dielectric breakdown must be protected by a leakage breaker or the like. Further, if possible, it is desired to monitor the decrease in the insulation resistance value in the electric device and prevent the dielectric breakdown without operating the earth-leakage circuit breaker. The insulation resistance is a performance value indicating the insulation performance between the electric circuit and the ground in the electric device, that is, a performance value indicating the difficulty of the flow of leakage current. On the other hand, although the earth-leakage circuit breaker can detect the leakage current from the device to the ground, it is difficult to measure a slight change in the insulation resistance due to the deterioration of the insulation, which is a state in which the insulation performance is deteriorated.

Machine tools or robots used at production sites in factories use a number of motors and cables that supply power to the motors (hereinafter referred to as "motor power cables"). In this motor power cable, the operation of bending and extending and the operation of sliding are repeated during use. Therefore, the motor power cable deteriorates over time. Further, the insulating material between the housing of the motor and the motor coil is also a member whose insulation deteriorates over time.

Normally, even if the insulation of the motor and the motor power cable deteriorates, the earth-leakage circuit breaker connected to the system operates and the entire device stops when a sufficiently large leakage current flows. Therefore, there is no safety problem. However, when the earth-leakage circuit breaker is activated, the device suddenly stops, which has a great influence on production. In addition, the earth-leakage circuit breaker simply electrically disconnects the device from the system, and the location of the cause of the leakage is unclear, so that it takes time to recover the device. Therefore, there is a need for a mechanism that sensitively detects a decrease in insulation resistance value.

Against such a technical background, the following Patent Document 1 discloses a technique for detecting a decrease in insulation resistance value. Specifically, in Patent Document 1, while the operation of the motor drive amplifier is stopped, the contact of the electromagnetic contactor is turned on for a specified time, and the three-phase power is rectified by the rectifier circuit to charge the smoothing capacitor. After that, the voltage of the smoothing capacitor is discharged, and when the specified voltage is reached, the contacts of the two switches are closed to form a closed circuit. Then, by comparing the voltage across the detection resistance in the closed circuit with the reference value, a decrease in the insulation resistance value is detected. In the technique of Patent Document 1, since the power supply for measuring the insulation resistance is a smoothing capacitor, there is an advantage that a decrease in the insulation resistance value can be detected regardless of the grounding method of the input power supply.

Japanese Unexamined Patent Publication No. 2005-110400

As described above, in the technique of Patent Document 1, since the power supply for measuring the insulation resistance is a capacitor, the insulation resistance cannot be measured unless the capacitor is charged. On the other hand, if the insulation deterioration of the motor or the motor power cable is progressing, the insulation resistance may be very small. In this state, if the power supply voltage is applied to the rectifier circuit to start charging the capacitor, an excessive current may flow in the motor control device and the internal circuit may be damaged. Therefore, the technique of Patent Document 1 has a problem that the device may be damaged before the decrease in the insulation resistance value is detected, and the deterioration of the insulation performance cannot be detected safely and surely.

The present disclosure has been made in view of the above, and an object of the present invention is to obtain a motor control device capable of safely and reliably detecting deterioration of insulation performance.

In order to solve the above-mentioned problems and achieve the object, the motor control device according to the present disclosure includes a rectifier circuit, a switch, a smoothing capacitor, an inverter circuit, a control unit, a voltage generation circuit, and a voltage detection circuit. To prepare for. The rectifier circuit converts AC power from AC power to DC power. The switch is located between the AC power supply and the rectifier circuit. The smoothing capacitor smoothes the DC power. The inverter circuit converts DC power into AC power supplied to the motor. The control unit outputs a signal for controlling continuity and non-conduction of the switching element of the inverter circuit, and outputs a signal for switching between continuity and non-conduction of the switch. The voltage generation circuit draws in the voltage of each phase wiring in the power supply voltage supply cable connecting the AC power supply and the switch, and generates an insulation resistance voltage corresponding to the insulation resistance. The voltage detection circuit detects the insulation resistance voltage generated in the voltage generation circuit.

According to the motor control device according to the present disclosure, there is an effect that deterioration of insulation performance can be detected safely and surely.

The figure which shows the structural example of the motor control device in Embodiment 1. The figure which shows the operation waveform of the main part in the motor control apparatus of Embodiment 1. The figure which shows the structural example of the insulation resistance detection circuit provided in the motor control apparatus of Embodiment 1. The figure which shows the operation waveform of the main part in the voltage generation circuit provided in the motor control apparatus of Embodiment 1. The figure provided for the explanation of the ground fault current which can flow when the motor control device shown in FIG. 1 does not have an insulation resistance detection circuit. The first figure which provides the operation description of the main part in the motor control apparatus of Embodiment 1. The second figure which provides the operation description of the main part in the motor control apparatus of Embodiment 1. FIG. 3 for explaining the operation of a main part in the motor control device of the first embodiment. A block diagram showing an example of a hardware configuration for realizing the function of the control unit in the first embodiment. A block diagram showing another example of the hardware configuration for realizing the function of the control unit in the first embodiment. The figure which shows the structural example of the motor control device in Embodiment 2. The figure which shows the structural example of the insulation resistance detection circuit provided in the motor control apparatus of Embodiment 2. The first figure which provides the operation description of the main part in the motor control apparatus of Embodiment 2. The second figure which provides the operation description of the main part in the motor control apparatus of Embodiment 2. FIG. 3 for explaining the operation of a main part in the motor control device of the second embodiment. FIG. 4 is provided for explaining the operation of a main part of the motor control device according to the second embodiment. The figure which shows the structural example of the motor control device in Embodiment 3. The figure which shows the structural example of the insulation resistance detection circuit provided in the motor control apparatus of Embodiment 3. The first figure which provides the operation description of the main part in the motor control apparatus of Embodiment 3. The second figure which provides the operation description of the main part in the motor control apparatus of Embodiment 3. FIG. 3 for explaining the operation of a main part in the motor control device of the third embodiment.

The motor control device according to the embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are examples, and the scope of the present disclosure is not limited by the following embodiments. Further, in the following description, the word "connection" includes both a case where components are directly connected to each other and a case where components are indirectly connected to each other via other components. I'm out.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of the motor control device 1 according to the first embodiment. As shown in FIG. 1, the motor control device 1 is arranged between an AC power source 2 which is an input power source and a motor 3 which is an example of an electric device. The motor control device 1 receives AC power from the AC power supply 2 via the switch 4. The motor control device 1 supplies electric power to the motor 3 to drive the motor 3. If necessary, the motor control device 1 controls the variable speed of the motor 3. The AC power supply 2 and the switch 4 are connected by a power supply voltage supply cable 5. The motor control device 1 and the motor 3 are connected by a motor power cable 6. That is, the AC power to the motor 3 is supplied via the motor power cable 6.

The AC power supply 2 is a three-phase AC power supply that generates a three-phase AC voltage. The AC power supply 2 includes three terminals 2R, 2S, and 2T. Terminal 2R is a terminal to which R-phase AC voltage is output, terminal 2S is a terminal to which S-phase AC voltage is output, and terminal 2T is a terminal to which T-phase AC voltage is output.

Generally, the motor control device 1 cuts off the power supply from the AC power supply 2 when the system is stopped. Therefore, a switch 4 is arranged between the AC power supply 2 and the motor control device 1. An example of the switch 4 is an electromagnetic contactor. The switch 4 opens and closes the electrical connection between the AC power supply 2 and the motor control device 1, and conducts and cuts off the power supply.

The switch 4 includes three input terminals 41, 42, 43 and three output terminals 44, 45, 46. The switch 4 is arranged between the AC power supply 2 and the rectifier circuit 7 described later. When the switch 4 conducts, the terminal 2R and the input terminal 41 are connected, the terminal 2S and the input terminal 42 are connected, and the terminal 2T and the input terminal 43 are connected. At this time, the power input to the input terminal 41 is output from the output terminal 44, the power input to the input terminal 42 is output from the output terminal 45, and the power input to the input terminal 43 is output from the output terminal 46. To.

The switch 4 is a non-conducting switch as standard. The switch 4 receives a switch switching signal (hereinafter referred to as “SW switching signal”) CS transmitted from the motor control device 1 and switches between conduction and non-conduction. The SW switching signal CS is a signal that takes a high level or low level potential. For example, when the SW switching signal CS reaches the High level, the input terminals 41, 42, 43 of the switch 4 and the corresponding output terminals 44, 45, 46 are individually conductive, and the SW switching signal CS becomes the Low level. When it becomes, it returns to non-conduction. The standard SW switching signal CS is a Low level signal. Therefore, the switch 4 is in a non-conducting state until the SW switching signal CS reaches the High level.

The motor control device 1 includes AC input terminals 71, 72, 73 that receive AC power from the AC power supply 2, and AC output terminals 83, 84, 85 that output AC power supplied to the motor 3. The power supply voltage supply cable is between the output terminal 44 of the switch 4 and the AC input terminal 71, between the output terminal 45 of the switch 4 and the AC input terminal 72, and between the output terminal 46 of the switch 4 and the AC input terminal 73. It is connected via 5.

The motor control device 1 includes a rectifier circuit 7, a smoothing capacitor C1, an inverter circuit 8, an insulation resistance detection circuit 9, and a control unit 10.

The rectifier circuit 7 includes the above-mentioned AC input terminals 71, 72, 73, a DC output terminal 74, and a DC output terminal 75. The rectifier circuit 7 is a full-wave rectifier circuit that converts three-phase AC power from the AC power supply 2 into DC power. The DC output terminal 74 is a terminal that outputs a potential on the high potential side (hereinafter referred to as "P potential") of the two terminals that output the converted DC power, and the DC output terminal 75 is a low potential. It is a terminal that outputs the side potential (hereinafter referred to as "N potential"). In this paper, the N potential may be referred to as the "first potential" and the P potential may be referred to as the "second potential".

The smoothing capacitor C1 is a capacitor that smoothes the DC power converted by the rectifier circuit 7. One end of the smoothing capacitor C1 is connected to a DC output terminal 74 that outputs a P potential, and the other end of the smoothing capacitor C1 is connected to a DC output terminal 75 that outputs an N potential.

The inverter circuit 8 includes a DC input terminal 81 having a P potential as an input potential, a DC input terminal 82 having an N potential as an input potential, and the above-mentioned AC output terminals 83, 84, 85. The inverter circuit 8 has a plurality of switching elements connected by a three-phase bridge. The inverter circuit 8 converts the DC power converted by the rectifier circuit 7 into AC power supplied to the motor 3. The DC input terminal 81 is connected to one end of the smoothing capacitor C1, and the DC input terminal 82 is connected to the other end of the smoothing capacitor C1. The AC output terminals 83, 84, 85 are connected to the motor 3 via the motor power cable 6.

The insulation resistance detection circuit 9 is a circuit that sends an insulation resistance detection value VR, which is a voltage detection value for calculating the insulation resistance, to the control unit 10. The control unit 10 receives the insulation resistance detection value VR transmitted from the insulation resistance detection circuit 9. The control unit 10 generates a drive command DS, which is a signal for controlling conduction and non-conduction of each switching element of the inverter circuit 8, and outputs the drive command DS to the inverter circuit 8. Further, the control unit 10 generates a SW switching signal CS for switching between conduction and non-conduction of the switch 4 and outputs the SW switching signal CS to the switch 4.

The drive command DS is a signal that takes a high level or low level potential. When the drive command DS is a high level signal, the switching element conducts. When the drive command DS is a Low level signal, the switching element becomes non-conducting. The standard of the drive command DS is Low level. Therefore, the switching element is in a non-conducting state until the high level signal is transmitted from the control unit 10.

As described above, the motor control device 1 receives the AC power from the AC power supply 2 via the switch 4 by the rectifying circuit 7, changes the received AC power to DC power, and then re-uses the AC power to the motor 3. And drives the motor 3. When the system is stopped, the switch 4 is controlled to be non-conducting to cut off the power supply from the AC power supply 2 to the motor control device 1. On the other hand, when the motor 3 is driven, the switch 4 is controlled to be conductive, and power is supplied from the AC power supply 2 to the motor control device 1. These operations are the basic operations of the motor control device 1.

FIG. 2 is a diagram showing an operation waveform of a main part in the motor control device 1 of the first embodiment. The horizontal axis of FIG. 2 represents time. Further, the upper part of FIG. 2 shows the power supply voltage for one phase output from the AC power supply 2, and the middle upper part shows the SW switching signal CS to the switch 4. Further, in the middle and lower stages of FIG. 2, among the voltages input to the AC input terminals 71, 72, 73 of the rectifier circuit 7, the voltage of the input terminal having the same phase as the power supply voltage shown in the upper stage is shown, and the lower stage is shown. The part shows the waveform of the voltage between the P potential and the N potential.

As shown in FIG. 2, when the switch 4 is in the cutoff state, the AC power supply 2 is not supplied to the rectifier circuit 7. On the other hand, when the switch 4 conducts, a power supply voltage is applied to the rectifier circuit 7, and a voltage is generated between the P potential and the N potential with the passage of time.

FIG. 3 is a diagram showing a configuration example of the insulation resistance detection circuit 9 included in the motor control device 1 of the first embodiment. FIG. 3 shows an example in which the insulation resistance detection circuit 9 is arranged between the power supply voltage supply cable 5 and the N potential. The insulation resistance detection circuit 9 includes a voltage generation circuit 31 and a voltage detection circuit 32.

The voltage generation circuit 31 is a circuit that draws in the voltage of each phase wiring in the power supply voltage supply cable 5 connecting the AC power supply 2 and the switch 4 to generate an insulation resistance voltage corresponding to the insulation resistance. The voltage detection circuit 32 is a circuit that detects the insulation resistance voltage generated in the voltage generation circuit 31.

The voltage generation circuit 31 includes diodes D1, D2, D3, a current limiting resistor 35, and a detection resistor 36. In the voltage generation circuit 31, the anode of the diode D1 is connected to the T phase of the power supply voltage supply cable 5, the anode of the diode D2 is connected to the S phase of the power supply voltage supply cable 5, and the anode of the diode D3 is the power supply voltage supply cable 5. It is connected to the R phase of. That is, the anode of each diode is connected to the corresponding phase wiring of the power supply voltage supply cable 5. Further, each cathode of the diodes D1, D2, and D3 is commonly connected to one end of the current limiting resistor 35. The other end of the current limiting resistor 35 is connected to one end of the detection resistor 36, and the other end of the detection resistor 36 is connected to the N potential. Further, both ends of the detection resistor 36 are connected to the voltage detection circuit 32.

FIG. 4 is a diagram showing an operation waveform of a main part in the voltage generation circuit 31 included in the motor control device 1 of the first embodiment. First, when a power supply voltage is applied from the AC power supply 2, the power supply voltage supply cable 5 has a sinusoidal voltage that changes between the maximum voltage Vmax and the minimum voltage Vmin as shown in the upper right part of FIG. Appears. In FIG. 4, for example, V [TS] is a voltage of the T phase with respect to the S phase, that is, a line voltage between the T phase and the S phase. Hereinafter, V [RS] is the line voltage between the R phase and the S phase, V [RT] is the line voltage between the R phase and the T phase, and V [ST] is the line between the S phase and the T phase. The inter-voltage, V [SR] is the line voltage between the S phase and the R phase, and V [TR] is the line voltage between the T phase and the R phase. At this time, the diodes D1, D2, and D3 are conducted by the diode connected to the phase to which the maximum line voltage among the six line voltages is applied. Therefore, as shown in the lower right part of FIG. 4, each cathode of the diodes D1, D2, and D3 commonly connected has a voltage corresponding to the potential difference between the maximum voltage of each line voltage and the N potential. appear.

FIG. 5 is a diagram for explaining the ground fault current that can flow when the motor control device 1 shown in FIG. 1 is not provided with the insulation resistance detection circuit 9. For example, when a ground fault has occurred in the motor power cable 6, if the switch 4 is conducted while the smoothing capacitor C1 is not charged, the ground fault current in the path shown by the two-dot chain line shown in FIG. Can flow. When the smoothing capacitor C1 is charged, the electric charge accumulated in the smoothing capacitor C1 limits the magnitude of the ground fault current, so that the ground fault current does not become an overcurrent. On the other hand, when the smoothing capacitor C1 is not charged, the ground fault current flows through the smoothing capacitor C1, so that the ground fault current can become an overcurrent. Since this overcurrent flows through the diode on the P potential side in the inverter circuit 8, the diode on the P potential side may be damaged. Further, depending on the phase of the power supply voltage, a ground fault current flows in the direction opposite to that in FIG. In this case, the diode on the N potential side in the inverter circuit 8 may be damaged. Although the case where the ground fault has occurred in the motor power cable 6 has been described here, an overcurrent in the same path may flow even when the ground fault has occurred in the motor 3.

As described above, when a ground fault has occurred in the motor control system including the motor control device 1, if the switch 4 is conducted while the smoothing capacitor C1 is not charged, the element of the inverter circuit 8 will be damaged. There is.

Next, the operation of the main part in the motor control device 1 of the first embodiment will be described with reference to the drawings of FIGS. 6, 7, and 8. 6, FIG. 7 and FIG. 8 are the first, second and third views provided for explaining the operation of the main part in the motor control device 1 of the first embodiment, respectively.

First, as described above, in the motor control system, the switch 4 is made non-conducting in order to cut off the power supply to the motor 3 when the system is stopped. Further, when the motor 3 is operated, the switch 4 is conducted in order to supply electric power from the AC power supply 2 to the motor control device 1.

On the other hand, even when the switch 4 is cut off, if the insulation performance of the entire system deteriorates, the ground fault current of the path shown by the thick broken line in FIG. 6 flows. In FIG. 6, assuming that the insulation performance of the motor power cable 6 has deteriorated, the insulation resistance 37 is shown between the motor power cable 6 and the ground. When the insulation performance of the motor 3 deteriorates, an insulation resistance 37 is formed between the motor 3 and the ground.

When the insulation performance of the motor power cable 6 deteriorates, a ground fault current flows from the power supply voltage supply cable 5 toward the N potential via the diodes D1, D2, and D3. Then, the ground fault current flowing into the N potential returns to the AC power supply 2 via the inverter circuit 8, the motor power cable 6, and the insulation resistor 37. This ground fault current can be suppressed by adjusting the resistance value of the current limiting resistor 35. This makes it possible to protect the circuit of the motor control system. Even when the insulation resistance is 0 [Ω], it is possible to protect the circuit of the motor control system by setting the current limiting resistor 35 to an appropriate resistance value.

The voltage of the detection resistor 36 is divided together with the current limiting resistor 35 and the insulation resistance 37 to be detected, and is converted into a voltage suitable for the voltage detection circuit 32. Specifically, as shown in FIG. 7, a voltage ΔV is generated between both ends of the detection resistor 36. This voltage ΔV is the above-mentioned insulation resistance voltage. In the first embodiment, the insulation resistance voltage is a voltage based on the N potential. The voltage detection circuit 32 detects this voltage ΔV and sends the detected value to the control unit 10. The detected value of the voltage ΔV is the above-mentioned insulation resistance detected value VR. The control unit 10 calculates the insulation resistance value, which is the resistance value of the insulation resistance 37, based on the insulation resistance detection value VR.

The voltage generation circuit 31 and the voltage detection circuit 32 are supplemented. In the voltage generation circuit 31, the current flowing through the detection resistor 36 can be suppressed to a low current. Therefore, the voltage detection circuit 32 can be configured by using an electronic component such as a photocoupler.

FIG. 8 simply shows the equivalent circuit of the motor control system when the insulation performance deteriorates. In FIG. 8, Vin is a voltage that appears at the cathodes of the diodes D1, D2, and D3. Further, R1 is the resistance value of the current limiting resistor 35, R2 is the resistance value of the detection resistor 36, and R is the resistance value of the insulation resistance 37, that is, the insulation resistance value. Further, I is a current flowing through the voltage generation circuit 31 of the insulation resistance detection circuit 9. At this time, the following equations (1) and (2) hold.

Further, by eliminating the current I from the above equations (1) and (2), the following equation (3) can be obtained.

Therefore, the control unit 10 can obtain the insulation resistance value R, which is the resistance value of the insulation resistance 37, by performing the calculation of the above equation (3).

FIG. 9 is a block diagram showing an example of a hardware configuration for realizing the function of the control unit 10 in the first embodiment. When the function of the control unit 10 in the first embodiment is realized, as shown in FIG. 9, the processor 200 that performs the calculation, the memory 202 in which the program read by the processor 200 is stored, and the input / output of the signal are realized. It can be configured to include the interface 204 for performing the above.

The processor 200 is an example of a calculation means. The processor 200 may be a computing means called a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Further, the memory 202 includes a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Program ROM), and an EPROM (registered trademark) (Electrically EPROM). Examples thereof include magnetic discs, flexible discs, optical discs, compact discs, mini discs, and DVDs (Digital Versailles Disc).

The memory 202 stores a program that executes the function of the control unit 10 according to the first embodiment. The processor 200 sends and receives necessary information via the interface 204, the processor 200 executes a program stored in the memory 202, and the processor 200 refers to a table stored in the memory 202 to perform the above-mentioned processing. It can be carried out. The calculation result by the processor 200 can be stored in the memory 202.

Further, when the function of the control unit 10 in the first embodiment is realized, the configuration shown in FIG. 10 may be used. FIG. 10 is a block diagram showing another example of the hardware configuration for realizing the function of the control unit 10 in the first embodiment. In FIG. 10, the processor 200 and the memory 202 shown in FIG. 9 are replaced with the processing circuit 203. The processing circuit 203 corresponds to a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The information input to the processing circuit 203 and the information output from the processing circuit 203 can be obtained via the interface 204.

The control unit 10 holds a threshold value for determining the deterioration of the insulation performance in the memory 202 or the processing circuit 203, and compares the calculated insulation resistance value R with the threshold value. When the insulation resistance value R is below the threshold value, the control unit 10 leaves the SW switching signal CS as the Low level signal. As a result, it is possible to prevent the power supply voltage from being applied to the rectifier circuit 7, and thus it is possible to prevent damage due to overcurrent.

When the insulation resistance value R of the motor 3 or the motor power cable 6 is sufficiently large, the potential difference generated between the power supply voltage supply cable 5 and the N potential is extremely small, so that the value of the current I flowing through the insulation resistance detection circuit 9 is small. , The value of the voltage ΔV shown in the above equation (2) also becomes small. As a result, the insulation resistance value R calculated by the above equation (3) becomes large, and the insulation resistance value R exceeds the threshold value.

When the insulation resistance value R exceeds the threshold value, the control unit 10 switches the SW switching signal CS to the High level signal. This makes it possible to drive the motor 3 based on the basic operation of the motor control device 1 described above.

As described above, according to the motor control device 1 of the first embodiment, the voltage generation circuit 31 draws in and insulates the voltage of each phase wiring in the power supply voltage supply cable 5 connecting the AC power supply 2 and the switch 4. An insulation resistance voltage corresponding to the resistance 37 is generated. The voltage detection circuit 32 detects the insulation resistance voltage generated in the voltage generation circuit 31. The motor control device 1 can detect a ground fault based on the detected value of the insulation resistance voltage. Further, the motor control device 1 can detect deterioration in the insulation performance of the motor 3 or the motor power cable 6 before conducting the switch 4. This makes it possible to safely and reliably detect deterioration in insulation performance.

Further, according to the motor control device 1 of the first embodiment, the control unit 10 is a detection value of the voltage detection circuit 32 when the switch 4 arranged between the AC power supply 2 and the rectifier circuit 7 is non-conducting. By calculating the insulation resistance value R based on the above and comparing the calculated insulation resistance value R with a preset threshold value, the continuity and non-conduction of the switch 4 can be controlled. As a result, it is possible to prevent failures of each circuit constituting the motor control system including the motor control device 1. Preventing failure of each circuit also leads to reduction of maintenance cost and time of the motor control system. Further, the motor 3 can be operated by detecting the decrease in the insulation resistance value R in advance and removing the cause of the decrease in the insulation resistance value R. This makes it possible to shorten the time required to restore the motor control system and improve the reliability of the motor control system. Further, the motor control system can be automatically restored by removing the factor that the insulation resistance value R is lowered.

Embodiment 2.
FIG. 11 is a diagram showing a configuration example of the motor control device 1A according to the second embodiment. In the motor control device 1A according to the second embodiment, the insulation resistance detection circuit 9 is replaced with the insulation resistance detection circuit 9A in the configuration of the motor control device 1 according to the first embodiment shown in FIG. Other configurations are the same as or equivalent to those in FIG. 1, and the same or equivalent components are indicated by the same reference numerals, and duplicate explanations are omitted.

FIG. 12 is a diagram showing a configuration example of the insulation resistance detection circuit 9A included in the motor control device 1A of the second embodiment. Comparing the insulation resistance detection circuit 9A shown in FIG. 12 with the insulation resistance detection circuit 9 shown in FIG. 3, the voltage generation circuit 31 is replaced by the voltage generation circuit 31A, and the voltage detection circuit 32 is replaced by the voltage detection circuit 32A. ing.

The voltage generation circuit 31A draws in the voltage of each phase wiring in the power supply voltage supply cable 5 connecting the AC power supply 2 and the switch 4, and generates an insulation resistance voltage corresponding to the insulation resistance. Specifically, the voltage generation circuit 31A includes diodes D1, D2, D3 and a current limiting resistor 35. In the voltage generation circuit 31A, the connections of the diodes D1, D2, and D3 are the same as those in the first embodiment. One end of the current limiting resistance 35 is connected to each cathode of the diodes D1, D2, D3 commonly connected, and the other end of the current limiting resistance 35 is connected to the P potential. In the voltage generation circuit 31A of the second embodiment, the insulation resistance voltage corresponding to the insulation resistance is generated at the P potential to which the other end of the current limiting resistance 35 is connected. Therefore, the voltage detection circuit 32A detects the insulation resistance voltage generated in the P potential of the voltage generation circuit 31A based on the N potential, and sends the detected value to the control unit 10 as the insulation resistance detection value VR.

Next, the operation of the main part in the motor control device 1A of the second embodiment will be described with reference to the drawings of FIGS. 13, 14, 15, and 16. 13, FIG. 14, FIG. 15 and FIG. 16 are the first, second, third and fourth views provided for explaining the operation of the main part in the motor control device 1A of the second embodiment, respectively.

If the insulation performance of the entire system deteriorates while the switch 4 is shut off, a ground fault current in the path shown by the alternate long and short dash line in FIG. 13 flows. In FIG. 13, the insulation resistance 37 is shown between the motor power cable 6 and the ground on the assumption that the insulation performance of the motor power cable 6 has deteriorated.

When the insulation performance of the motor power cable 6 deteriorates, a ground fault current flows from the power supply voltage supply cable 5 toward the P potential via the diodes D1, D2, and D3. Since the smoothing capacitor C1 is not charged, the ground fault current flowing into the P potential returns to the AC power supply 2 via the inverter circuit 8, the motor power cable 6, and the insulation resistor 37 while charging the smoothing capacitor C1.

As shown in the middle part on the right side of FIG. 14, a voltage corresponding to the potential difference between the maximum voltage Vmax of each line voltage and the P potential appears at each cathode of the diodes D1, D2, and D3 that are commonly connected. The smoothing capacitor C1 is charged by this voltage. As the charging of the smoothing capacitor C1 progresses, the voltage of the smoothing capacitor C1 (hereinafter referred to as “capacitor voltage”) ΔVpn gradually approaches the maximum voltage Vmax as shown in the lower right part of FIG.

FIG. 15 simply shows the equivalent circuit of the motor control system when the insulation performance deteriorates. In FIG. 15, Vin is a voltage that appears at the cathodes of the diodes D1, D2, and D3. Further, R1 is the resistance value of the current limiting resistor 35, C is the capacitance value of the smoothing capacitor C1, and R is the resistance value of the insulating resistor 37. Further, I is a current flowing through the voltage generation circuit 31A. At this time, the following equations (4) and (5) hold.

In the above equation (4), ε is the base of the natural logarithm and t is the charging time. Further, as shown in the above equation (5), Rsum is the total resistance value obtained by adding the resistance value R1 of the current limiting resistor 35 and the insulation resistance value R of the insulation resistance 37. By eliminating the total resistance value Rsum from the above equations (4) and (5), the following equation (6) is obtained.

The voltage detection circuit 32A measures in advance the capacitor voltage ΔVpn (Vpn1) when a time t1 has elapsed since the control power supply (not shown) was turned on in a normal state, that is, in a state where the insulation performance has not deteriorated. The control unit 10 stores this measured value in the memory 202 as normal data. Then, at the time of evaluation of the insulation performance, the voltage detection circuit 32A measures the capacitor voltage ΔVpn (Vpn1 *) when the time t1 elapses after the control power supply is turned on, and notifies the control unit 10 of the measurement result. The control unit 10 compares the capacitor voltage ΔVpn (Vpn1 *) at the time of evaluation with the corresponding capacitor voltage ΔVpn (Vpn1) at the normal time. When the capacitor voltage ΔVpn (Vpn1 *) at the time of evaluation is larger than the capacitor voltage ΔVpn (Vpn1) at the normal time, the control unit 10 can determine that the insulation resistance value R has decreased.

Next, the points to be noted in this determination will be described. First, since the normal data is representative data measured in advance, it is possible that individual differences may occur depending on the product. Therefore, in order to improve the accuracy of the determination, it is desirable to compare the data at a plurality of times. Here, an example of measuring at three different times t1, t2, t3 (t1 <t2 <t3) will be described. It is assumed that the data of the capacitor voltage ΔVpn (Vpn1, Vpn2, Vpn3) in the normal state is measured in advance and stored in the memory 202 of the control unit 10.

At the time of evaluation of the insulation performance, the voltage detection circuit 32A measures the capacitor voltage ΔVpn (Vpn1 *, Vpn2 *, Vpn3 *) when the time t1, t2, t3 elapses after the control power supply is turned on, and controls the measurement result. Notify unit 10. The control unit 10 compares the average value of the capacitor voltage ΔVpn (Vpn1 *, Vpn2 *, Vpn3 *) at the time of evaluation with the average value of the corresponding capacitor voltage ΔVpn (Vpn1, Vpn2, Vpn3) at the normal time. When the average value of the capacitor voltage ΔVpn at the time of evaluation is larger than the average value of the capacitor voltage ΔVpn (Vpn1, Vpn2, Vpn3) at the normal time, the control unit 10 determines that the insulation resistance value R is lowered. Can be done. By doing so, the accuracy of calculating the insulation resistance value R can be improved.

Further, the above equation (6) for calculating the insulation resistance value R includes a time t representing a charging time. As described above, since the time t is the time after the charging of the smoothing capacitor C1 is started, the time t1, t2, and t3 after the control power supply is turned on is not an accurate calculated value. FIG. 16 shows a waveform of a capacitor voltage ΔVpn in which charging starts at time 0 and changes with the passage of time. The time t0 is the time when the control power supply is turned on, and the times t01, t02, and t03 are arbitrary times for measuring the capacitor voltage ΔVpn. Further, ΔT is the time difference between the time 0 when charging starts and the time t0 when the control power supply starts up.

The time difference ΔT is measured in advance and stored in the memory 202 of the control unit 10. The control unit 10 calculates the insulation resistance value R using the above equation (6) under the condition that ΔVpn = Vpn1 * when the time t01 = t1 + ΔT. The insulation resistance value R is calculated in the same manner for the times t02 and t03.

As described above, according to the motor control device 1A of the second embodiment, the voltage generation circuit 31A draws in and insulates the voltage of each phase wiring in the power supply voltage supply cable 5 connecting the AC power supply 2 and the switch 4. An insulation resistance voltage corresponding to the resistance 37 is generated. The voltage detection circuit 32A detects the insulation resistance voltage generated in the voltage generation circuit 31A. Further, the control unit 10 calculates the insulation resistance value R based on the detection value of the voltage detection circuit 32A when the switch 4 arranged between the AC power supply 2 and the rectifier circuit 7 is non-conducting. Thereby, as in the first embodiment, it is possible to safely and surely detect the deterioration of the insulation performance. Further, as in the first embodiment, it is possible to prevent failures of each circuit constituting the motor control system including the motor control device 1A. Further, as in the first embodiment, the time until the restoration of the motor control system can be shortened, and the reliability of the motor control system can be improved. Further, as in the first embodiment, the motor control system can be automatically restored by removing the cause of the decrease in the insulation resistance value R.

Embodiment 3.
FIG. 17 is a diagram showing a configuration example of the motor control device 1B according to the third embodiment. In the motor control device 1B according to the third embodiment, in the configuration of the motor control device 1 according to the first embodiment shown in FIG. 1, the motor 13, the inverter circuit 15 that supplies AC power to the motor 13, the motor 13 and the inverter circuit A motor power cable 14 for connecting to the 15 is added. Further, in the motor control device 1B, the insulation resistance detection circuit 9 is replaced with the insulation resistance detection circuit 9B. Other configurations are the same as or equivalent to those in FIG. 1, and the same or equivalent components are indicated by the same reference numerals, and duplicate explanations are omitted. In this paper, the inverter circuit 8 may be referred to as a "first inverter circuit", and the inverter circuit 15 may be referred to as a "second inverter circuit".

The inverter circuit 15 includes a DC input terminal 151 having a P potential as an input potential, a DC input terminal 152 having an N potential as an input potential, and AC output terminals 153, 154, 155. The inverter circuit 15 has a plurality of switching elements connected by a three-phase bridge. The inverter circuit 15 converts the DC power converted by the rectifier circuit 7 into AC power supplied to the motor 13. The DC input terminal 151 is connected to one end of the smoothing capacitor C1, and the DC input terminal 152 is connected to the other end of the smoothing capacitor C1. The AC output terminals 153, 154, and 155 are connected to the motor 13 via the motor power cable 14. The control unit 10 generates a drive command DS1 which is a signal for controlling conduction and non-conduction of each switching element of the inverter circuit 8, and outputs the drive command DS1 to the inverter circuit 8. Further, the control unit 10 generates a drive command DS2 which is a signal for controlling conduction and non-conduction of each switching element of the inverter circuit 15 and outputs the drive command DS2 to the inverter circuit 15.

As described above, the motor control device 1B converts the smoothed DC power into the respective AC power in the inverter circuit corresponding to each motor and drives the corresponding motor. The basic operation of the motor control device 1B is the same as that of the first embodiment. In the case of the motor control device 1B, the inverter circuit 8 corresponds to the motor 3, and the inverter circuit 15 corresponds to the motor 13.

FIG. 18 is a diagram showing a configuration example of the insulation resistance detection circuit 9B included in the motor control device 1B of the third embodiment. Comparing the insulation resistance detection circuit 9B shown in FIG. 18 with the insulation resistance detection circuit 9 shown in FIG. 3, the voltage generation circuit 31 is replaced with the voltage generation circuit 31B. The voltage generation circuit 31B is a circuit that draws in the voltage of each phase wiring in the power supply voltage supply cable 5 connecting the AC power supply 2 and the switch 4 to generate an insulation resistance voltage according to the insulation resistance.

The voltage generation circuit 31B includes diodes D1, D2, D3, D4, D5, D6, circuit changeover switches 16 and 17, a current limiting resistor 35, and a detection resistor 36. The anode of the diode D1 is connected to the T phase of the power supply voltage supply cable 5, the anode of the diode D2 is connected to the S phase of the power supply voltage supply cable 5, and the anode of the diode D3 is connected to the R phase of the power supply voltage supply cable 5. The diode. That is, each anode in the set of diodes D1, D2, D3 is connected to the corresponding phase wiring of the power supply voltage supply cable 5. On the other hand, the cathode of the diode D4 is connected to the T phase of the power supply voltage supply cable 5, the cathode of the diode D5 is connected to the S phase of the power supply voltage supply cable 5, and the cathode of the diode D6 is connected to the R phase of the power supply voltage supply cable 5. Be connected. That is, each cathode in the set of diodes D4, D5, D6 is connected to the corresponding phase wiring of the power supply voltage supply cable 5.

Each cathode in the set of diodes D1, D2, D3 is commonly connected and is commonly connected to one end of the current limiting resistor 35 via the circuit changeover switch 17. Further, each anode in the set of diodes D4, D5, and D6 is commonly connected, and is commonly connected to one end of the current limiting resistor 35 via the circuit changeover switch 16. The other end of the current limiting resistor 35 is connected to one end of the detection resistor 36, and the other end of the detection resistor 36 is connected to the N potential. Further, both ends of the detection resistor 36 are connected to the voltage detection circuit 32. In this paper, each of the diodes D1, D2, and D3 may be referred to as a "first diode", and each of the diodes D4, D5, and D6 may be referred to as a "second diode". Further, in this paper, the circuit changeover switch 17 may be referred to as a "first circuit changeover switch", and the circuit changeover switch 16 may be referred to as a "second circuit changeover switch".

The circuit changeover switch 17 is a standard conductive switch, and the circuit changeover switch 16 is a standard non-conducting switch. The circuit changeover switch 17 receives the circuit changeover signal CX transmitted from the control unit 10 and switches between conduction and non-conduction. The circuit switching signal CX is a signal that takes a high level or low level potential. For example, when the circuit changeover signal CX reaches the High level, the circuit changeover switch 17 becomes non-conducting and the circuit changeover switch 16 conducts. When the circuit changeover signal CX reaches the Low level, the circuit changeover switch 17 returns to the conductive state, and the circuit changeover switch 16 returns to the non-conducting state. That is, the circuit changeover switch 16 has a conduction and non-conduction state opposite to that of the circuit changeover switch 17. The circuit switching signal CX is a standard low level signal. Therefore, the circuit changeover switch 17 is in a conductive state and the circuit changeover switch 16 is in a non-conducting state until the high level circuit changeover signal CX is transmitted from the control unit 10.

Next, the operation of the main part in the motor control device 1B of the third embodiment will be described with reference to the drawings of FIGS. 19, 20, and 21. 19, FIGS. 20, and 21 are the first, second, and third views provided for explaining the operation of the main part in the motor control device 1B of the third embodiment, respectively.

If the insulation performance of the entire system deteriorates while the switch 4 is shut off, a ground fault current in the path shown by the alternate long and short dash line in FIG. 19 flows. In FIG. 19, an insulation resistance 37 is shown between the motor power cable 6 and the ground on the assumption that the insulation performance of the motor power cable 6 has deteriorated. Since the circuit changeover switch 17 is conductive and the circuit changeover switch 16 is non-conducting, the path of the ground fault current is the same as that of the first embodiment shown in FIG.

Further, in FIG. 20, assuming that the insulation performance of the motor power cable 14 has deteriorated, the insulation resistance 38 is shown between the motor power cable 14 and the ground. The path of the ground fault current is the inverter circuit 15 and the motor power cable 14, but the states of the circuit changeover switches 16 and 17 are the same as those in FIG. 19, and the other paths are the same as those in FIG.

Next, the operation of identifying the motor power cable whose insulation performance has deteriorated will be described with reference to FIG. 21. First, the motor control device 1B calculates the insulation resistance value R based on the insulation resistance detection value VR. When the deterioration of the insulation performance is detected, the motor control device 1B protects the circuit of the motor control system. Next, the control unit 10 of the motor control device 1B switches the circuit switching signal CX from the Low level to the High level. As a result, the circuit changeover switch 16 becomes conductive, and the circuit changeover switch 17 becomes non-conducting. However, since the diodes D4, D5, and D6 do not allow current to flow from the potential of the power supply voltage supply cable 5 in the direction of the N potential, there is no path through which the current flows at this point, and a decrease in the insulation resistance value R cannot be detected. Therefore, the control unit 10 outputs a command (hereinafter referred to as "drive command DS1N") for conducting only the switching element on the N potential side to the inverter circuit 8. By this drive command DS1N, the switching element on the N potential side of the inverter circuit 8 becomes conductive. As a result, as shown in FIG. 21, a current flows in the direction opposite to that in FIGS. 19 and 20, and the detected insulation resistance value R becomes low. Next, the control unit 10 stops the output of the drive command DS1N to the inverter circuit 8 and outputs the drive command DS1N to the inverter circuit 15. In the case of the example of FIG. 21, since the insulation performance of the motor power cable 14 is not deteriorated, there is no path through which the current flows, and the detected insulation resistance value R becomes large. Although the deterioration detection of the insulation performance of the motor power cables 6 and 14 has been described here, the deterioration detection of the insulation performance of the motors 3 and 13 can also be performed by the same control.

When there are a plurality of inverter circuits, the circuit switching signal CX is set to High level, and the drive command DS1N is output to each inverter circuit in order. At this time, the low insulation resistance value R can be detected only when the drive command DS1N is output to the inverter circuit corresponding to the motor or the motor power cable whose insulation performance is deteriorated. Thereby, it is possible to identify the motor or the motor power cable whose insulation performance has deteriorated based on the detected insulation resistance value R. By using this method, it is possible to identify all the locations even if the insulation performance of a plurality of motors or motor power cables is deteriorated at the same time.

As described above, according to the motor control device 1B of the third embodiment, the voltage generation circuit 31B draws in and insulates the voltage of each phase wiring in the power supply voltage supply cable 5 connecting the AC power supply 2 and the switch 4. An insulation resistance voltage corresponding to the resistance 37 is generated. The voltage detection circuit 32B detects the insulation resistance voltage generated in the voltage generation circuit 31B. Further, the control unit 10 calculates the insulation resistance value R based on the detection value of the voltage detection circuit 32B when the switch 4 arranged between the AC power supply 2 and the rectifier circuit 7 is non-conducting. Thereby, as in the first embodiment, it is possible to safely and surely detect the deterioration of the insulation performance. Further, as in the first embodiment, it is possible to prevent failures of each circuit constituting the motor control system including the motor control device 1B. Further, as in the first embodiment, the time until the restoration of the motor control system can be shortened, and the reliability of the motor control system can be improved. Further, as in the first embodiment, the motor control system can be automatically restored by removing the cause of the decrease in the insulation resistance value R.

Further, according to the motor control device 1B of the third embodiment, the control unit 10 controls the circuit changeover switch 17 to be non-conducting and controls the circuit changeover switch 16 to be conductive by the circuit changeover signal CX. In this state, the control unit 10 deteriorates the insulation performance based on the insulation resistance value obtained when the drive commands for conducting only the switching elements on the N potential side are sequentially output to the inverter circuits 8 and 15. To identify. By using this method, even if the insulation performance of a plurality of motors or motor power cables is deteriorated at the same time, it is possible to identify all the parts.

The configuration shown in the above embodiments is an example, and can be combined with another known technique, or can be combined with each other, and deviates from the gist. It is also possible to omit or change a part of the configuration to the extent that it does not.

1,1A, 1B motor controller, 2 AC power supply, 2R, 2S, 2T terminal, 3,13 motor, 4 switch, 5 power supply voltage supply cable, 6,14 motor power cable, 7 rectifier circuit, 8,15 inverter circuit , 9, 9A, 9B Insulation resistance detection circuit, 10 control unit, 16, 17 circuit changeover switch, 31, 31A, 31B voltage generation circuit, 32, 32A voltage detection circuit, 35 current limiting resistance, 36 detection resistance, 37, 38 Insulation resistance, 41,42,43 input terminal, 44,45,46 output terminal, 71,72,73 AC input terminal, 74,75 DC output terminal, 81,82,151,152 DC input terminal, 83,84, 85,153,154,155 AC output terminal, 200 processor, 202 memory, 203 processing circuit, 204 interface, C1 smoothing capacitor, D1, D2, D3, D4, D5, D6 diode.

Claims (12)

A rectifier circuit that converts AC power from AC power to DC power,
A switch arranged between the AC power supply and the rectifier circuit,
A smoothing capacitor that smoothes the DC power,
An inverter circuit that converts the DC power into AC power supplied to the motor,
A control unit that outputs a signal for controlling continuity and non-conduction of the switching element of the inverter circuit and outputs a signal for switching between continuity and non-conduction of the switch.
A voltage generation circuit that draws in the voltage of each phase wiring in the power supply voltage supply cable that connects the AC power supply and the switch to generate an insulation resistance voltage according to the insulation resistance.
A voltage detection circuit that detects the insulation resistance voltage generated in the voltage generation circuit, and
Equipped with
Ground fault detection is performed based on the detection value of the voltage detection circuit when the switch is non-conducting.
A motor control device characterized by that . A rectifier circuit that converts AC power from AC power to DC power,
A switch arranged between the AC power supply and the rectifier circuit,
A smoothing capacitor that smoothes the DC power,
An inverter circuit that converts the DC power into AC power supplied to the motor,
A control unit that outputs a signal for controlling continuity and non-conduction of the switching element of the inverter circuit and outputs a signal for switching between continuity and non-conduction of the switch.
A voltage generation circuit that draws in the voltage of each phase wiring in the power supply voltage supply cable that connects the AC power supply and the switch to generate an insulation resistance voltage according to the insulation resistance.
A voltage detection circuit that detects the insulation resistance voltage generated in the voltage generation circuit, and
Equipped with
When the potential on the low potential side of the smoothing capacitor is the first potential and the potential on the high potential side is the second potential,
The voltage generation circuit is a motor control device characterized in that the insulation resistance voltage is generated with reference to the first potential. The motor control device according to claim 2 , wherein the voltage generation circuit includes a current limiting resistance. The voltage generation circuit is
A plurality of diodes in which each anode is connected to the corresponding phase wiring of the power supply voltage supply cable and each cathode is commonly connected to the current limiting resistor.
A detection resistor with one end connected to the current limiting resistor and the other end connected to the first potential.
Equipped with
The motor control device according to claim 3 , wherein the voltage detection circuit detects a voltage across the detection resistance. The voltage detection circuit is
The first circuit changeover switch and
A second circuit changeover switch whose conduction and non-conduction states are opposite to those of the first circuit changeover switch.
Equipped with
With a plurality of first diodes in which each anode is connected to the corresponding phase wiring of the power supply voltage supply cable and each cathode is commonly connected to the current limiting resistor via the first circuit changeover switch. ,
With a plurality of second diodes in which each cathode is connected to the corresponding phase wiring of the power supply voltage supply cable and each anode is commonly connected to the current limiting resistor via the second circuit changeover switch. ,
A detection resistor with one end connected to the current limiting resistor and the other end connected to the first potential.
Equipped with
The motor control device according to claim 3 , wherein the voltage detection circuit detects a voltage across the detection resistance. The inverter circuit includes first and second inverter circuits.
The control unit controls the first circuit changeover switch to be non-conducting by the circuit changeover signal, and controls the second circuit changeover switch to be conductive with respect to the first and second inverter circuits. The fifth aspect of the present invention is characterized in that the deteriorated portion of the insulation performance is specified based on the insulation resistance value obtained when the drive commands for conducting only the switching element on the first potential side are sequentially output. Motor control device. 13. The motor control device according to any one of the following items . A rectifier circuit that converts AC power from AC power to DC power,
A switch arranged between the AC power supply and the rectifier circuit,
A smoothing capacitor that smoothes the DC power,
An inverter circuit that converts the DC power into AC power supplied to the motor,
A control unit that outputs a signal for controlling continuity and non-conduction of the switching element of the inverter circuit and outputs a signal for switching between continuity and non-conduction of the switch.
A voltage generation circuit that draws in the voltage of each phase wiring in the power supply voltage supply cable that connects the AC power supply and the switch to generate an insulation resistance voltage according to the insulation resistance.
A voltage detection circuit that detects the insulation resistance voltage generated in the voltage generation circuit, and
Equipped with
When the potential on the low potential side of the smoothing capacitor is the first potential and the potential on the high potential side is the second potential,
The voltage generation circuit is a motor control device characterized in that the insulation resistance voltage is generated at the second potential. The motor control device according to claim 8 , wherein the voltage generation circuit includes a current limiting resistance. The voltage generating circuit comprises a plurality of diodes in which each anode is connected to the corresponding phase wiring of the power supply voltage supply cable and each cathode is commonly connected to the current limiting resistor.
The motor control device according to claim 9 , wherein the voltage detection circuit detects a voltage between the second potential and the first potential. The motor control according to any one of claims 1 to 10 , wherein the control unit controls power supply to the motor based on an insulation resistance value calculated based on the insulation resistance voltage. Device. The control unit according to any one of claims 1 to 11 , wherein the control unit outputs a signal for switching between continuity and non-conduction of the switch based on the insulation resistance value calculated based on the insulation resistance voltage. The motor control device described.

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