Motor drive device that calculates insulation resistance value of motor

Abstract

This motor drive device comprises: a motor drive unit that supplies a 3-phase motor current to a motor by applying a 3-phase output voltage to the motor; a control unit that outputs to the motor drive unit a command for controlling the output voltage of the motor drive unit; a DC current detection unit that detects a DC component of the motor current when the control unit outputs to the motor drive unit a command such that the output voltage includes a DC component; and an insulation resistance value calculation unit that calculates an insulation resistance value of the motor on the basis of information related to the output voltage when the control unit outputted the command to the motor drive unit and the DC component of the motor current detected by the DC current detection unit.

Description

Motor drive device for calculating motor insulation resistance

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

[0002] In motors installed in machine tools, etc., the insulation resistance of the motor coil (winding) against the ground (hereinafter sometimes referred to as the "motor insulation resistance") decreases over time due to oil infiltration and other factors. When the motor's insulation resistance decreases, a leakage current flows in the closed circuit consisting of the motor, motor drive device, and ground. When this leakage current flows in the motor drive device in addition to the normal motor drive current, the motor drive device may perform an overcurrent detection operation or trip a breaker installed in the input stage. As a result, the machine tool equipped with the motor may undergo an emergency shutdown. When such an emergency shutdown occurs, the machine tool may be shut down for an extended period of time to investigate the cause, resulting in a decrease in efficiency. For this reason, measuring the motor's insulation resistance is essential for the operation of the motor drive device.

[0003] JP 2015-122857 A JP 61-258645 A JP 2021-018163 A

[0004] There is a need for a technique that allows the insulation resistance value of a motor to be easily calculated even while the motor is being driven by a motor drive device.

[0005] According to one aspect of the present disclosure, a motor drive device includes a motor drive unit that supplies a three-phase motor current to the motor by applying a three-phase output voltage to the motor; a control unit that outputs a command to the motor drive unit to control the output voltage of the motor drive unit; a DC current detection unit that detects the DC component of the motor current when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component; and an insulation resistance value calculation unit that calculates an insulation resistance value of the motor based on information related to the output voltage when the control unit outputs the command to the motor drive unit and the DC component of the motor current detected by the DC current detection unit.

[0006] FIG. 1 is a circuit diagram showing a motor drive device according to first to third embodiments of the present disclosure. FIG. 2 is a circuit diagram showing an equivalent circuit on the AC motor side of the motor drive device shown in FIG. 1. FIG. 2 is a circuit diagram showing circuit components involved in a DC component in the equivalent circuit shown in FIG. 2A. FIG. 2 is a circuit diagram showing a case where a DC current detection unit, a DC voltage detection unit, and an insulation resistance value calculation unit are configured as analog circuits. FIG. 3 is a circuit diagram showing a motor drive device according to fourth to sixth embodiments of the present disclosure. FIG. 4 is a circuit diagram showing an equivalent circuit on the AC motor side of the motor drive device shown in FIG. 4, showing circuit components involved in a DC component. FIG. 3 is a flowchart showing an operation flow of a calculation process for a motor insulation resistance value in the motor drive devices according to the first, second, fourth, and fifth embodiments of the present disclosure. FIG. 4 is a flowchart showing an operation flow of a calculation process for a motor insulation resistance value in the motor drive devices according to the third and sixth embodiments of the present disclosure. FIG. 5 is a circuit diagram showing a motor drive device according to a seventh embodiment of the present disclosure. FIG. 6 is a circuit diagram showing a motor drive device according to an eighth embodiment of the present disclosure. FIG. 6 is a flowchart showing an operation flow of a calculation process for a motor insulation resistance value in the motor drive devices according to the seventh and eighth embodiments of the present disclosure. FIG. 7 is a circuit diagram showing a motor drive device according to a ninth embodiment of the present disclosure. 13 is a flowchart showing an operation flow of a process for calculating an insulation resistance value of a motor in a motor drive device according to a ninth embodiment of the present disclosure.

[0007] An embodiment of a motor drive device that calculates the insulation resistance value of a motor will be described below with reference to the drawings. In the following description, components having the same or similar functions will be assigned the same reference numerals. Duplicate descriptions of those components may be omitted. The scale of the drawings has been appropriately changed to facilitate understanding.

[0008] In the following description, "electrically connected" may be simply referred to as "connected." A converter that converts AC voltage supplied from an AC power source into DC voltage and outputs it to the DC side is also called a "rectifier," "rectifier device," "rectifier circuit," or "forward converter." An inverter that converts the DC voltage output from the converter into AC voltage for driving a motor and outputs it to the AC motor side is called a "motor drive unit." The "output voltage of the motor drive unit" refers to the voltage output to the AC side by the motor drive unit, which is an inverter. The terms "motor insulation resistance value" and "motor insulation resistance resistance value" refer to the resistance value of the insulation resistance of the motor coil (winding) with respect to the ground. The term "motor current" refers to the current flowing from the motor drive unit, which is an inverter, to the motor coil of the motor. The term "DC link" refers to the circuit portion that electrically connects the DC output side of the converter and the DC input side of the inverter. The term "DC link" is also called a "DC link unit," "DC link," "DC link unit," "DC bus," or "DC intermediate circuit." The "on operation" of a switching element means that the switching element is closed and an electric path is formed through the switching element. The "off operation" of a switching element means that the switching element is opened and an electric path through the switching element is interrupted. The numerical examples illustrated below are merely examples, and numerical values ​​other than those described here may also be used.

[0009] <Configuration of First Embodiment of Present Disclosure> FIG. 1 is a circuit diagram showing a motor drive device according to first to third embodiments of the present disclosure.

[0010] In the first embodiment of the present disclosure described below and in each embodiment and modified example described below, a case will be described in which a three-phase AC motor 3 is driven by a motor drive device 1 connected to a three-phase AC power supply 2. Furthermore, the number of phases of the AC power supply 2 is not particularly limited to this embodiment, and the AC power supply 2 may be, for example, three-phase or single-phase. Examples of the AC power supply 2 include a three-phase 400V AC power supply, a three-phase 200V AC power supply, a three-phase 600V AC power supply, and a single-phase 100V AC power supply. Machines equipped with the motor 3 include, for example, machine tools and robots.

[0011] The motor drive device 1 according to the first embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a DC current detection unit 13, a DC voltage detection unit 14, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). The other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices. Power lines for supplying power to drive the control unit 12, the DC current detection unit 13, the DC voltage detection unit 14, and the insulation resistance value calculation unit 15 are not shown.

[0012] The motor 3 has a U-phase motor coil 61U, a V-phase motor coil 61V, and a W-phase motor coil 61W. The U-phase motor coil 61U, the V-phase motor coil 61V, and the W-phase motor coil 61W are connected in a Y-connection (star connection). An insulation resistor 20 is present between the motor coils of the Y-connected motor 3 and the ground. The insulation resistance value R of the insulation resistor 20 m [Ω] is infinite if there is no degradation, and as degradation progresses, it gradually decreases from infinity to several MΩ, several hundred kΩ, etc. The motor drive device 1 according to the first embodiment of the present disclosure and each embodiment described later has an insulation resistance value R m It has the function of detecting [Ω].

[0013] The converter 10 converts AC voltage input from the AC power source 2 into DC voltage and outputs it to a DC link, which is the DC output side. The converter 10 is configured as a three-phase diode bridge circuit when a three-phase AC voltage is supplied from the AC power source 2, and as a single-phase diode bridge circuit when a single-phase AC voltage is supplied from the AC power source 2. In the illustrated example, the AC power source 2 is a three-phase AC power source, so the converter 10 is configured as a three-phase bridge circuit. Examples of the converter 10 include a diode rectifier, a 120-degree conduction rectifier, and a PWM switching control rectifier. For example, if the converter 10 is a 120-degree conduction rectifier or a PWM switching control rectifier, it is configured as a bridge circuit of switching elements and diodes connected in reverse parallel to the switching elements, and each switching element is controlled on and off in response to a drive command received from a higher-level control device (not shown) to perform bidirectional AC / DC power conversion. In this case, examples of the switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used. Although not shown here, a breaker, an electromagnetic contactor, a reactor, and the like may be provided on the AC input side of the converter 10 .

[0014] A DC link capacitor 16 is connected to the DC link between the converter 10 and the motor drive unit 11. The DC link capacitor 16 is sometimes referred to as a "DC link capacitor" or a "smoothing capacitor." The DC link capacitor 16 has the functions of suppressing oscillations in the DC output voltage of the converter 10 and storing DC charge used by the motor drive unit 11 to generate AC voltage. Examples of the DC link capacitor 16 include an electrolytic capacitor and a film capacitor. A pre-charging circuit for pre-charging the DC link capacitor 16 may be provided, but is not shown here.

[0015] The DC side of the motor drive unit 11 is connected to the converter 10 via a DC link. The AC side of the motor drive unit 11 is connected to the motor 3 via a U-phase power line 51U, a V-phase power line 51V, and a W-phase power line 51W.

[0016] The motor drive unit 11 is an inverter that outputs a three-phase output voltage to the AC side and applies it to the motor 3, thereby supplying a three-phase motor current to the motor coil of the motor 3. The motor 3 is driven based on the motor current supplied from the motor drive unit 11. The motor drive unit 11 is configured as a three-phase bridge circuit of switching elements and diodes connected in antiparallel to the switching elements. The motor drive unit 11 controls the output voltage of the motor drive unit 11 by turning the switching elements on and off in response to commands from the control unit 12. Examples of switching elements include FETs, IGBTs, thyristors, GTOs, and transistors, but other switching elements may also be used.

[0017] The control unit 12 generates commands to control the output voltage of the motor drive unit 11 and outputs these commands to the motor drive unit 11. The commands generated by the control unit 12 include commands to cause the motor drive unit 11 to perform powering operation and commands to cause the motor drive unit 11 to perform regenerative operation. In powering operation, the motor drive unit 11 converts a DC voltage input from the DC link side into an AC voltage for driving the motor 3 and outputs it to the motor 3 side. In regenerative operation, the motor drive unit 11 converts an AC voltage regenerated by the motor 3 into a DC voltage and returns it to the DC link side. When the control unit 12 outputs a command to the motor drive unit 11 to perform powering operation or regenerative operation, the motor drive unit 11 outputs an AC output voltage.

[0018] Furthermore, in the first embodiment of the present disclosure and the second, fourth, fifth, and seventh to ninth embodiments and modifications described below, when calculating the insulation resistance value of the motor 3, the control unit 12 generates a command to cause the output voltage of each phase of the motor drive unit 11 to further include a DC component (a command to cause a DC component to be superimposed on the output voltage of each phase of the motor drive unit 11), and outputs the command to the motor drive unit 11. Upon receiving the command, the motor drive unit 11 outputs three-phase output voltages in which the DC component used to calculate the insulation resistance value of the motor 3 is superimposed on each of the three-phase AC voltages for driving the motor 3.

[0019] A U-phase shunt resistor 31U is provided on the U-phase power line 51U. A V-phase shunt resistor 31V is provided on the V-phase power line 51V. A W-phase shunt resistor 31W is provided on the W-phase power line 51W. The U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W have the same resistance value. By making the U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W have the same resistance value, three-phase symmetry of the voltages and currents of the U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W is maintained. Furthermore, by setting the resistance values ​​of U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W to the same magnitude, the DC components of the voltages and currents of U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are all the same. Therefore, the DC components of the line voltages of U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are canceled out, thereby suppressing the influence of the DC components of the output voltage of motor drive unit 11 and the motor current on the rotational drive of motor 3.

[0020] The DC current detection unit 13 detects the DC component of the motor current when the control unit 12 outputs to the motor drive unit 11 a command to cause the output voltage of the motor drive unit 11 to include a DC component. In the first embodiment of the present disclosure, the DC current detection unit 13 detects the DC component of the motor current for one phase.

[0021] In the illustrated example, the DC current detection unit 13 detects the DC component of the W-phase motor current. The DC current detection unit 13 includes a low-pass filter 30, an amplifier circuit 35, and an AD converter 36. A U-phase shunt resistor 31U provided on the W-phase power line 51W is connected to the input side of the DC current detection unit 13. The AD converter 36 may use a successive approximation type, a delta-sigma type, a double integral type, a flash type (parallel comparison type), or a pipeline type. A low-pass filter 30 is connected to the input side of the AD converter 36 via an amplifier circuit 35. The low-pass filter 30 includes filter resistors 32 and 33 and a filter capacitor 34. The filter capacitor 34 is connected between the non-inverting input terminal (+) and the inverting input terminal (-) of the amplifier circuit 35, and the filter resistors 32 and 33 are connected to both terminals of the filter capacitor 34, respectively. When a current flows through the W-phase power line 51W, a potential difference occurs between both terminals of the W-phase shunt resistor 31W. Each potential signal is input to the non-inverting input terminal (+) and the inverting input terminal (-) of the amplifier circuit 35 via the low-pass filter 30, and only the DC component of the W-phase motor current is extracted by the low-pass filter 30. The DC component of the W-phase motor current output from the low-pass filter 30 is amplified by the amplifier circuit 35 and input to the AD converter 36. The AD converter 36 converts the DC component I of the W-phase motor current in the form of digital data into a digital signal. d Output.

[0022] The DC voltage detection unit 14 detects the DC component of the output voltage of the motor drive unit 11 as information related to the output voltage of the motor drive unit 11 when the control unit 12 outputs to the motor drive unit 11 a command to cause the output voltage of the motor drive unit 11 to include a DC component. In the first embodiment of the present disclosure, the DC voltage detection unit 14 detects the DC component of the output voltage for one phase.

[0023] In the illustrated example, the DC voltage detection unit 14 detects the DC component of the W-phase output voltage of the motor drive unit 11. The DC voltage detection unit 14 includes a low-pass filter 40, an amplifier circuit 43, and an AD converter 44. The W-phase power line 51W is connected to the input side of the DC voltage detection unit 14. The AD converter 44 may use a successive approximation type, a delta-sigma type, a double integration type, a flash type (parallel comparison type), or a pipeline type for analog-to-digital conversion. The input side of the AD converter 44 is connected to the low-pass filter 40 via the amplifier circuit 43. The low-pass filter 40 includes a filter resistor 41 and a filter capacitor 42. Only the DC component of the W-phase output voltage is extracted by the low-pass filter 40. The DC component of the W-phase output voltage output from the low-pass filter 40 is amplified by the amplifier circuit 43 and input to the AD converter 44. The AD converter 44 converts the DC component V of the W-phase output voltage in digital data format into a digital signal. d Output.

[0024] The insulation resistance value calculation unit 15 calculates the insulation resistance value of the motor 3 based on information related to the output voltage when the control unit 12 outputs a command to the motor drive unit 11 to cause the output voltage of the motor drive unit 11 to include a DC component, and on the DC component of the motor current detected by the DC current detection unit. In the first embodiment of the present disclosure, the DC component of the output voltage for one phase detected by the DC voltage detection unit 14 is used as the information related to the output voltage of the motor drive unit 11.

[0025] Fig. 2A is a circuit diagram showing an equivalent circuit on the AC motor side of the motor drive device shown in Fig. 1. Fig. 2B is a circuit diagram showing circuit components in which a DC component is involved in the equivalent circuit shown in Fig. 2A.

[0026] As shown in FIG. 2A, the AC output of the U-phase of the motor drive unit 11 in FIG. 1 is a voltage V U The AC output of the V phase is represented by the AC voltage source 11U. V The AC voltage source is represented by 11V, and the AC output of the W phase is represented by voltage V WThe resistance values ​​of U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are the same, so when control unit 12 outputs a command to motor drive unit 11 to include a DC component in the output voltage of motor drive unit 11, the DC component included in the output voltage of each phase is represented by the voltage V of DC voltage source 71, which has the same magnitude. d The DC voltage detector 14 in FIG. d Detect.

[0027] The motor coils 61U, 61V, and 61W can be considered to be short-circuited with respect to the DC components of the current and voltage. Furthermore, the capacitors, which are capacitive circuit components, can be ignored because they are open with respect to the DC components of the current and voltage. Therefore, as shown in FIG. 2B, the DC component V d and I d The circuit components involved are the U-phase shunt resistor 31U, the V-phase shunt resistor 31V, the W-phase shunt resistor 31W, and the insulation resistor 20 of the motor 3. By solving the circuit equation in the circuit shown in FIG. 2B, the resistance value Rm of the insulation resistor 20 of the motor 3 can be obtained. The DC component of the motor current detected by the DC current detection unit 13 is expressed as I d and the DC component of the output voltage detected by the DC voltage detection unit 14 is V d In this case, the resistance value Rm of the insulation resistor 20 of the motor 3 is expressed as in Equation 1.

[0028]

[0029] Therefore, in the first embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V of the output voltage detected by the DC voltage detection unit 14. d and the DC component I of the motor current detected by the DC current detection unit 13. d Based on the above, the resistance value Rm of the insulation resistor 20 of the motor 3 is calculated according to Equation 1.

[0030] 1 are equipped with AD converters, and digital calculations are performed in the insulation resistance value calculation unit 15. As a modification, the DC current detection unit 13, the DC voltage detection unit 14, and the insulation resistance value calculation unit 15 may be configured with analog circuits.

[0031] FIG. 3 is a circuit diagram showing a case where the DC current detector, DC voltage detector, and insulation resistance value calculator are configured as analog circuits.

[0032] The DC current detection unit 13 includes a low-pass filter 30 and an amplifier circuit 35. The low-pass filter 30 and the amplifier circuit 35 are analog circuits. A U-phase shunt resistor 31U, which is provided on the W-phase power line 51W, is connected to the input side of the DC current detection unit 13. The low-pass filter 30 includes filter resistors 32 and 33 and a filter capacitor 34. The filter capacitor 34 is connected between the non-inverting input terminal (+) and the inverting input terminal (-) of the amplifier circuit 35, and the filter resistors 32 and 33 are connected to both terminals of the filter capacitor 34. When a current flows on the W-phase power line 51W, a potential difference occurs between the two terminals of the W-phase shunt resistor 31W, and the low-pass filter 30 extracts only the DC component from each potential signal. The DC components of each potential signal output from the low-pass filter 30 are input to the non-inverting input terminal (+) and the inverting input terminal (-) of the amplifier circuit 35. The amplifier circuit 35 receives the DC component I of the W-phase motor current in the form of an analog signal. d Output.

[0033] The DC voltage detection unit 14 includes a low-pass filter 40 and an amplifier circuit 43. The W-phase power line 51W is connected to the input side of the DC voltage detection unit 14. The low-pass filter 40 includes a filter resistor 41 and a filter capacitor 42. The low-pass filter 40 extracts only the DC component of the W-phase output voltage. The DC component of the W-phase output voltage output from the low-pass filter 40 is amplified by the amplifier circuit 43. The amplifier circuit 43 amplifies the DC component V of the W-phase output voltage in the form of an analog signal. d Output.

[0034] The insulation resistance value calculation unit 15 includes a triple amplifier circuit 51 and an analog divider circuit 52. The triple amplifier circuit 51 amplifies the W-phase motor current in the form of an analog signal output from the amplifier circuit 35 by a factor of three, which is expressed as "3I" in Equation 1. d The analog divider circuit 52 calculates the DC component V of the W-phase output voltage according to Equation 1. d is three times the DC component of the W-phase motor current, 3I d and outputs the resistance value Rm of the insulation resistor 20 of the motor 3.

[0035] <Configuration of Second Embodiment of the Present Disclosure> The second embodiment of the present disclosure is a modified example of the first embodiment of the present disclosure. In the second embodiment of the present disclosure, the offsets of the DC current detection unit 13 and the DC voltage detection unit 14 are canceled to improve the calculation accuracy of the insulation resistance value.

[0036] A circuit diagram of a motor drive device 1 according to a second embodiment of the present disclosure is as shown in Fig. 1. The motor drive device 1 according to the second embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a DC current detection unit 13, a DC voltage detection unit 14, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). Here, the other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0037] The converter 10, motor drive unit 11, control unit 12, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0038] In the second embodiment of the present disclosure, when the control unit 12 outputs a command to the motor drive unit 11 to cause the output voltage of the motor drive unit 11 to include a DC component, the DC voltage detection unit 14 detects the DC component of the output voltage and the DC current detection unit 13 detects the DC component of the motor current multiple times. The insulation resistance value calculation unit 15 calculates the insulation resistance value of the motor 3 based on the DC components of the multiple output voltages detected by the DC voltage detection unit 14 and the DC components of the multiple motor currents detected by the DC current detection unit 13.

[0039] The DC component of the motor current detected by the DC current detection unit 13 at the first timing when the control unit 12 outputs to the motor drive unit 11 a command to include a DC component in the output voltage of the motor drive unit 11 is defined as I. d1 The DC component of the output voltage detected by the DC voltage detection unit 14 at this first timing is V d1 The DC component of the motor current detected by the DC current detection unit 13 at the second timing when the control unit 12 outputs to the motor drive unit 11 a command to include a DC component in the output voltage of the motor drive unit 11 is defined as I d2 The DC component of the output voltage detected by the DC voltage detection unit at this second timing is V d2 In this case, the resistance value Rm of the insulation resistor 20 of the motor 3 is expressed as in Equation 2.

[0040]

[0041] In the second embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V of the output voltage detected by the DC voltage detection unit 14. d1 and V d2 and the DC component I of the motor current detected by the DC current detection unit 13. d1 and I d2 Based on this, the resistance value Rm of the insulation resistor 20 of the motor 3 is calculated according to Equation 2.

[0042] As shown in Equation 2, the DC components of the motor currents detected by the DC current detection unit 13 at different timings are subtracted, thereby canceling the offset of the DC current detection unit 13. Similarly, the DC components of the output voltages detected by the DC voltage detection unit 14 at different timings are subtracted, thereby canceling the offset of the DC voltage detection unit 14. Therefore, according to the second embodiment of the present disclosure, the calculation accuracy of the insulation resistance value is improved.

[0043] <Configuration of the Third Embodiment of the Present Disclosure> The third embodiment of the present disclosure is a modified example of the first and second embodiments of the present disclosure. The third embodiment of the present disclosure is applied to a case where the output voltage of the motor drive unit 11 contains a DC component for some reason, even if the control unit 12 does not output a command to cause the output voltage of the motor drive unit 11 to contain a DC component.

[0044] A circuit diagram of a motor drive device 1 according to a third embodiment of the present disclosure is as shown in Fig. 1. The motor drive device 1 according to the third embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a DC current detection unit 13, a DC voltage detection unit 14, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). Here, the other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0045] The converter 10, motor drive unit 11, DC current detection unit 13, DC voltage detection unit 14, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first or second embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0046] The control unit 12 generates commands to control the output voltage of each phase of the motor drive unit 11 and outputs these commands to the motor drive unit 11. The commands generated by the control unit 12 include commands to cause the motor drive unit 11 to perform powering operation and regenerative operation. However, the commands output by the control unit 12 do not include commands to cause the output voltage of each phase of the motor drive unit 11 to include a DC component.

[0047] If the output voltage of the motor drive unit 11 contains a DC component for some reason even if the control unit 12 does not output a command to cause the output voltage of the motor drive unit 11 to contain a DC component, the insulation resistance value calculation unit 15 calculates the resistance value Rm of the insulation resistor 20 of the motor 3 in accordance with Equation 1 or Equation 2, based on the DC component of the output voltage detected by the DC voltage detection unit 14 and the DC component of the motor current detected by the DC current detection unit 13.

[0048] <Configuration of Fourth Embodiment of Present Disclosure> FIG. 4 is a circuit diagram showing a motor drive device according to fourth to sixth embodiments of the present disclosure.

[0049] In the fourth embodiment of the present disclosure and the fifth and sixth embodiments described later, the insulation resistance value R of the motor 3 is calculated based on the three-phase motor current and the three-phase output voltage of the motor drive unit 11. m According to the fourth embodiment of the present disclosure, even if the motor current is unbalanced among the three phases or the output voltage of the motor drive unit 11 is unbalanced among the three phases, the insulation resistance value R m can be calculated accurately.

[0050] A motor drive device 1 according to a fourth embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a U-phase DC current detection unit 13U, a V-phase DC current detection unit 13V, a W-phase DC current detection unit 13W, a U-phase DC voltage detection unit 14U, a V-phase DC voltage detection unit 14V, a W-phase DC voltage detection unit 14W, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). The other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices. Note that power lines that supply power to drive the control unit 12, the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, the W-phase DC current detection unit 13W, the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, the W-phase DC voltage detection unit 14W, and the insulation resistance value calculation unit 15 are not shown in the figure.

[0051] The converter 10, motor drive unit 11, control unit 12, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0052] The U-phase DC current detection unit 13U detects the DC component I of the U-phase motor current when the control unit 12 outputs a command to the motor drive unit 11 to make the U-phase output voltage of the motor drive unit 11 include a DC component. U The V-phase DC current detection unit 13V detects the DC component I of the U-phase motor current when the control unit 12 outputs a command to the motor drive unit 11 to make the V-phase output voltage of the motor drive unit 11 include a DC component. V The W-phase DC current detection unit 13W detects the DC component I of the U-phase motor current when the control unit 12 outputs a command to the motor drive unit 11 to make the W-phase output voltage of the motor drive unit 11 include a DC component. WThe configurations of the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W are the same as those described for the DC current detection unit 13 in the first embodiment. Furthermore, the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W may be configured as analog circuits as described with reference to FIG. 3.

[0053] The U-phase DC voltage detection unit 14U detects the DC component V of the U-phase output voltage of the motor drive unit 11 as information related to the U-phase output voltage when the control unit 12 outputs a command to the motor drive unit 11 to make the U-phase output voltage of the motor drive unit 11 include a DC component. U The V-phase DC voltage detection unit 14V detects the DC component V of the V-phase output voltage of the motor drive unit 11 as information related to the V-phase output voltage when the control unit 12 outputs a command to the motor drive unit 11 to make the V-phase output voltage of the motor drive unit 11 include a DC component. V The W-phase DC voltage detection unit 14W detects the DC component V of the W-phase output voltage of the motor drive unit 11 as information related to the W-phase output voltage when the control unit 12 outputs a command to the motor drive unit 11 to make the W-phase output voltage of the motor drive unit 11 include a DC component. W The configurations of the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W are the same as those described for the DC voltage detection unit 14 in the first embodiment. Furthermore, the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W may be configured as analog circuits as described with reference to FIG. 3.

[0054] FIG. 5 is a circuit diagram showing an equivalent circuit on the AC motor side of the motor drive device shown in FIG. 4, and shows circuit components involving DC components.

[0055] As shown in Figure 5, the motor coils 61U, 61V, and 61W can be considered to be short-circuited with respect to the DC components of the current and voltage. Furthermore, the capacitors, which are capacitive circuit components, can also be ignored because they are open with respect to the DC components of the current and voltage. Therefore, as shown in Figure 5, the DC component V du, V dv and V dw and I du , I dv and I dw The circuit components involved are the U-phase shunt resistor 31U, the V-phase shunt resistor 31V, the W-phase shunt resistor 31W, and the insulation resistor 20 of the motor 3. By solving the circuit equation in the circuit shown in Figure 5, the resistance value Rm of the insulation resistor 20 of the motor 3 can be obtained. The DC component of the U-phase motor current detected by the U-phase DC current detection unit 13U is expressed as I du and the DC component of the V-phase motor current detected by the V-phase DC current detection unit 13V is I dv and the DC component of the W-phase motor current detected by the W-phase DC current detection unit 13W is I dw and the DC component of the U-phase output voltage detected by the U-phase DC voltage detection unit 14U is V du and the DC component of the V-phase output voltage detected by the V-phase DC voltage detection unit 14V is V dv and the DC component of the W-phase output voltage detected by the W-phase DC voltage detection unit 14W is V dw Then, the insulation resistance value calculation unit 15 calculates the resistance value Rm of the insulation resistor 20 of the motor 3 as shown in Equation 3.

[0056]

[0057] In the fourth embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V of the output voltage detected by the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W. du , V dv and V dw and the DC component I of the motor current detected by the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W. du , I dv and I dw Based on this, the resistance value Rm of the insulation resistor 20 of the motor 3 is calculated according to Equation 3.

[0058] <Configuration of Fifth Embodiment of the Present Disclosure> The fifth embodiment of the present disclosure is a modification of the fourth embodiment of the present disclosure. In the fifth embodiment of the present disclosure, offsets of the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, the W-phase DC current detection unit 13W, the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W are canceled to improve the calculation accuracy of the insulation resistance value.

[0059] A circuit diagram of a motor drive device 1 according to a fifth embodiment of the present disclosure is as shown in FIG. 4. The motor drive device 1 according to the fifth embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a U-phase DC current detection unit 13U, a V-phase DC current detection unit 13V, a W-phase DC current detection unit 13W, a U-phase DC voltage detection unit 14U, a V-phase DC voltage detection unit 14V, a W-phase DC voltage detection unit 14W, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). The other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0060] The converter 10, motor drive unit 11, control unit 12, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0061] In the fifth embodiment of the present disclosure, when control unit 12 outputs a command to motor drive unit 11 to cause the output voltage of motor drive unit 11 to include a DC component, U-phase DC voltage detection unit 14U, V-phase DC voltage detection unit 14V, and W-phase DC voltage detection unit 14W detect the DC component of the output voltage and U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, and W-phase DC current detection unit 13W detect the DC component of the motor current multiple times. Insulation resistance value calculation unit 15 calculates the insulation resistance value of motor 3 based on the DC components of the multiple output voltages detected by U-phase DC voltage detection unit 14U, V-phase DC voltage detection unit 14V, and W-phase DC voltage detection unit 14W and the DC components of the multiple motor currents detected by U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, and W-phase DC current detection unit 13W.

[0062] The DC component of the U-phase motor current detected by the U-phase DC current detection unit 13U at the first timing when the control unit 12 outputs a command to the motor drive unit 11 to include a DC component in the output voltage of each phase is defined as I. du1 , the DC component of the V-phase motor current detected by the V-phase DC current detection unit 13V is I dv1 , the DC component of the W-phase motor current detected by the W-phase DC current detection unit 13W is I dw1 The DC component of the U-phase output voltage detected by the U-phase DC voltage detection unit 14U at the first timing is V du1 , the DC component of the V-phase output voltage detected by the V-phase DC voltage detection unit 14V is V dv1 , the DC component of the W-phase output voltage detected by the W-phase DC voltage detection unit 14W is V dw1 Furthermore, the DC component of the U-phase motor current detected by the U-phase DC current detection unit 13U at the second timing when the control unit 12 outputs a command to the motor drive unit 11 to cause the output voltage of each phase to include a DC component is defined as I du2 , the DC component of the V-phase motor current detected by the V-phase DC current detection unit 13V is I dv2 , the DC component of the W-phase motor current detected by the W-phase DC current detection unit 13W is I dw2 The DC component of the U-phase output voltage detected by the U-phase DC voltage detection unit 14U at the second timing is Vdu2 , the DC component of the V-phase output voltage detected by the V-phase DC voltage detection unit 14V is V dv2 , the DC component of the W-phase output voltage detected by the W-phase DC voltage detection unit 14W is V dw2 In this case, the resistance value Rm of the insulation resistor 20 of the motor 3 is expressed as in Equation 4.

[0063]

[0064] In the fifth embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the resistance value Rm of the insulation resistor 20 of the motor 3 according to Equation 4, based on the DC component of the output voltage of each phase detected by the DC voltage detection unit 14 and the DC component of the motor current of each phase detected by the DC current detection unit 13.

[0065] As shown in Equation 4, the DC components of the motor currents of the respective phases detected by the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W at different timings are subtracted, thereby canceling out the offsets of the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W. Similarly, the DC components of the output voltages of the respective phases detected by the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W at different timings are subtracted, thereby canceling out the offsets of the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W. Therefore, according to the fifth embodiment of the present disclosure, the accuracy of calculating the insulation resistance value is improved.

[0066] <Configuration of Sixth Embodiment of the Present Disclosure> The sixth embodiment of the present disclosure is a modification of the fourth and fifth embodiments of the present disclosure. The sixth embodiment of the present disclosure is applied to a case where a DC component is included in the output voltage of each phase of the motor drive unit 11 for some reason, even if the control unit 12 does not output a command to cause the output voltage of each phase of the motor drive unit 11 to include a DC component.

[0067] 1 shows a circuit diagram of a motor drive device 1 according to a sixth embodiment of the present disclosure. The motor drive device 1 according to the sixth embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a U-phase DC current detection unit 13U, a V-phase DC current detection unit 13V, a W-phase DC current detection unit 13W, a U-phase DC voltage detection unit 14U, a V-phase DC voltage detection unit 14V, a W-phase DC voltage detection unit 14W, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). The other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0068] The converter 10, motor drive unit 11, U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, W-phase DC current detection unit 13W, U-phase DC voltage detection unit 14U, V-phase DC voltage detection unit 14V, W-phase DC voltage detection unit 14W, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the fourth or fifth embodiment. Furthermore, the AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0069] The control unit 12 generates commands to control the output voltage of each phase of the motor drive unit 11 and outputs these commands to the motor drive unit 11. The commands generated by the control unit 12 include commands to cause the motor drive unit 11 to perform powering operation and regenerative operation. However, the commands output by the control unit 12 do not include commands to cause the output voltage of each phase of the motor drive unit 11 to include a DC component.

[0070] If the output voltage of the motor drive unit 11 contains a DC component for some reason even if the control unit 12 does not output a command to cause the output voltage of the motor drive unit 11 to contain a DC component, the insulation resistance value calculation unit 15 calculates the resistance value Rm of the insulation resistor 20 of the motor 3 in accordance with Equation 3 or Equation 4 based on the DC component of the output voltage detected by the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W and the DC component of the motor current detected by the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W.

[0071] <Operations of the first, second, fourth, and fifth embodiments of the present disclosure>

[0072] FIG. 6 is a flowchart showing an operation flow of a process for calculating the insulation resistance value of a motor in the motor drive devices according to the first, second, fourth, and fifth embodiments of the present disclosure.

[0073] When the motor drive device 1 is operating, in step S101, the control unit 12 generates a command to cause the output voltage of each phase of the motor drive unit 11 to further include a DC component (a command to cause a DC component to be superimposed on the output voltage of each phase of the motor drive unit 11), and outputs the command to the motor drive unit 11.

[0074] In step S102, the DC component of the motor current is detected. In the first and second embodiments of the present disclosure, the DC current detection unit 13 detects the DC component of the motor current of one phase. In the fourth and fifth embodiments of the present disclosure, the U-phase DC current detection unit 13U detects the DC component of the motor current of the U phase, the V-phase DC current detection unit 13V detects the DC component of the motor current of the V phase, and the W-phase DC current detection unit 13W detects the DC component of the motor current of the W phase.

[0075] In step S103, the DC component of the output voltage of the motor drive unit 11 is detected. In the first and second embodiments of the present disclosure, the DC voltage detection unit 14 detects the DC component of the output voltage of one phase. In the fourth and fifth embodiments of the present disclosure, the U-phase DC voltage detection unit 14U detects the DC component of the output voltage of the U phase, the V-phase DC voltage detection unit 14V detects the DC component of the output voltage of the V phase, and the W-phase DC voltage detection unit 14W detects the DC component of the output voltage of the W phase.

[0076] The process of step S102 and the process of step S103 are executed at the same time.

[0077] In step S104, the insulation resistance value of the motor 3 is calculated.

[0078] <Operations of the third and sixth embodiments of the present disclosure>

[0079] FIG. 7 is a flowchart showing the operation flow of the process of calculating the insulation resistance value of the motor in the motor drive devices according to the third and sixth embodiments of the present disclosure.

[0080] When motor drive device 1 is operating, in step S201, control unit 12 generates commands to control the output voltage of each phase of motor drive unit 11 and outputs these commands to motor drive unit 11. The commands generated by control unit 12 include commands to cause motor drive unit 11 to perform powering operation and commands to cause motor drive unit 11 to perform regenerative operation. However, the commands output by control unit 12 do not include commands to cause the output voltage of each phase of motor drive unit 11 to include a DC component.

[0081] In step S202, the DC component of the motor current is detected. In a third embodiment of the present disclosure, the DC current detection unit 13 detects the DC component of the motor current of one phase. In a sixth embodiment of the present disclosure, the U-phase DC current detection unit 13U detects the DC component of the motor current of the U phase, the V-phase DC current detection unit 13V detects the DC component of the motor current of the V phase, and the W-phase DC current detection unit 13W detects the DC component of the motor current of the W phase.

[0082] In step S203, the DC component of the output voltage of the motor drive unit 11 is detected. In a third embodiment of the present disclosure, the DC voltage detection unit 14 detects the DC component of the output voltage of one phase. In a sixth embodiment of the present disclosure, the U-phase DC voltage detection unit 14U detects the DC component of the output voltage of the U phase, the V-phase DC voltage detection unit 14V detects the DC component of the output voltage of the V phase, and the W-phase DC voltage detection unit 14W detects the DC component of the output voltage of the W phase.

[0083] The process of step S202 and the process of step S203 are executed at the same time.

[0084] In step S204, the insulation resistance value of the motor 3 is calculated.

[0085] <Configuration of Seventh Embodiment of the Present Disclosure> In the seventh embodiment of the present disclosure, the DC component of a value corresponding to a command that causes the output voltage to contain a DC component is used instead of the DC component of the output voltage of the motor drive unit 11 detected by the DC voltage detection unit 14, as information related to the output voltage of the motor drive unit 11 used in calculating the insulation resistance value of the motor 3. The "value corresponding to the command" refers to a converted value that can be used in calculating the insulation resistance value of the motor 3, and the "DC component of the value corresponding to the command" refers to the DC component of that converted value.

[0086] FIG. 8 is a circuit diagram showing a motor driving device according to a seventh embodiment of the present disclosure.

[0087] A motor drive device 1 according to a seventh embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a DC current detection unit 13, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). Here, the other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0088] The converter 10, motor drive unit 11, control unit 12, DC current detection unit 13, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0089] In the seventh embodiment of the present disclosure, as information related to the output voltage of the motor drive unit 11, instead of the DC component of the output voltage for one phase of the motor drive unit 11 detected by the DC voltage detection unit 14, a DC component V d * The insulation resistance value calculation unit 15 calculates the DC component V d * The insulation resistance value calculation unit 15 obtains the DC component V of the value corresponding to the command to include a DC component in the output voltage. d * and the DC component I of the motor current detected by the DC current detection unit 13. d Based on the above, the resistance value of the insulation resistor 20 of the motor 3 is calculated according to Equation 5.

[0090]

[0091] Alternatively, in accordance with Equation 6 instead of Equation 5, the insulation resistance value calculation unit 15 calculates the DC component V d1 * and V d2 * and DC components I of the multiple motor currents detected by the DC current detection unit 13. d1 and I d2 The resistance value Rm of the insulation resistor 20 of the motor 3 may be calculated based on the above.

[0092] The DC component of the motor current detected by the DC current detection unit 13 at the first timing when the control unit 12 outputs to the motor drive unit 11 a command to include a DC component in the output voltage of the motor drive unit 11 is defined as I. d1The DC component of the value corresponding to the command at this first timing is V d1 * The DC component of the motor current detected by the DC current detection unit 13 at the second timing when the control unit 12 outputs to the motor drive unit 11 a command to include a DC component in the output voltage of the motor drive unit 11 is defined as I d2 The DC component of the value corresponding to the command at this second timing is V d2 * V d2 In this case, the resistance value Rm of the insulation resistor 20 of the motor 3 is expressed as in Equation 6.

[0093]

[0094] In the seventh embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V d1 * and V d2 * and the DC component I of the motor current detected by the DC current detection unit 13. d1 and I d2 Based on the above, the resistance value Rm of the insulation resistor 20 of the motor 3 is calculated according to Equation 6.

[0095] <Configuration of Eighth Embodiment of the Present Disclosure> In the eighth embodiment of the present disclosure, as information related to the three-phase output voltage of the motor drive unit 11 used to calculate the insulation resistance value of the motor 3, instead of the DC component of the three-phase output voltage of the motor drive unit 11 detected by the DC voltage detection unit 14, a DC component of a value corresponding to a three-phase command that causes the output voltage to include a DC component is used.

[0096] FIG. 9 is a circuit diagram showing a motor driving device according to an eighth embodiment of the present disclosure.

[0097] A motor drive device 1 according to an eighth embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a U-phase DC current detection unit 13U, a V-phase DC current detection unit 13V, a W-phase DC current detection unit 13W, an insulation resistance value calculation unit 15, a DC link capacitor 16, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). Here, the other circuits may include, for example, a processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0098] The converter 10, motor drive unit 11, control unit 12, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment. The U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, and W-phase DC current detection unit 13W are as described in the fourth embodiment. The U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, and W-phase DC current detection unit 13W may be configured as analog circuits, as described with reference to FIG. 3 .

[0099] In the eighth embodiment of the present disclosure, instead of the DC components of the three-phase output voltage of the motor drive unit 11 detected by the DC voltage detection unit 14, the DC components V du * , V dv * and V dw * The insulation resistance value calculation unit 15 calculates the DC component V corresponding to the three-phase command to include a DC component in the output voltage. du * , V dv * and V dw *The insulation resistance value calculation unit 15 obtains the DC component V of the value corresponding to the command for three phases that causes the output voltage to include a DC component. du * , V dv * and V dw * and the DC component I of the three-phase motor current detected by the DC current detection unit 13. du , I dv and I dw Based on the above, the resistance value of the insulation resistor 20 of the motor 3 is calculated according to Equation 7.

[0100]

[0101] In the eighth embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V du * , V dv * and V dw * and the DC component I of the motor current detected by the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W. du , I dv and I dw Based on the above, the resistance value Rm of the insulation resistor 20 of the motor 3 is calculated according to Equation 7.

[0102] Alternatively, in accordance with Equation 8 instead of Equation 7, the insulation resistance value calculation unit 15 calculates the DC component V du1 * , V dv1 * , V dw1 * , V du2 * , V dv2 * and V dw2 * and DC components I of the multiple motor currents detected by the DC current detection unit 13. du1 , I dv1 , I dw1 , I du2 , I dv2 and I dw2The resistance value Rm of the insulation resistor 20 of the motor 3 may be calculated based on the above.

[0103] The DC components of the motor currents of the three phases detected by the DC current detection unit 13 at the first timing when the control unit 12 outputs to the motor drive unit 11 a command to include a DC component in the output voltage of the motor drive unit 11 are defined as I. du1 , I dv1 and I dw1 The DC component of the value corresponding to the command for each of the three phases at this first timing is V du1 * , V dv1 * and V dw1 * The DC component of the motor current detected by the DC current detection unit 13 at the second timing when the control unit 12 outputs to the motor drive unit 11 a command for each of the three phases so that the output voltage of the motor drive unit 11 contains a DC component is defined as I. du2 , I dv2 and I dw2 and the DC component V of the value corresponding to the command for each of the three phases at this second timing is du2 * , V dv2 * and V dw2 * In this case, the resistance value Rm of the insulation resistor 20 of the motor 3 is expressed as in Equation 8.

[0104]

[0105] In the eighth embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V du1 * , V dv1 * , V dw1 * , V du2 * , V dv2 * and V dw2 * and the DC component I of the motor current detected by the DC current detection unit 13. du1 , I dv1 , I dw1 , Idu2 , I dv2 and I dw2 Based on the above, the resistance value Rm of the insulation resistor 20 of the motor 3 is calculated according to Equation 8.

[0106] <Operation of Seventh and Eighth Embodiments of the Present Disclosure> FIG. 10 is a flowchart showing the operation flow of the process of calculating the insulation resistance value of the motor in the motor drive device according to the seventh and eighth embodiments of the present disclosure.

[0107] When the motor drive device 1 is operating, in step S301, the control unit 12 generates a command to cause the output voltage of each phase of the motor drive unit 11 to further include a DC component (a command to cause a DC component to be superimposed on the output voltage of each phase of the motor drive unit 11), and outputs the command to the motor drive unit 11.

[0108] In step S302, the DC component of the motor current is detected. In a seventh embodiment of the present disclosure, the DC current detection unit 13 detects the DC component of the motor current of one phase. In an eighth embodiment of the present disclosure, the U-phase DC current detection unit 13U detects the DC component of the motor current of the U phase, the V-phase DC current detection unit 13V detects the DC component of the motor current of the V phase, and the W-phase DC current detection unit 13W detects the DC component of the motor current of the W phase.

[0109] In step S303, the insulation resistance value calculation unit 15 acquires a DC component of a value corresponding to a command for causing the output voltage of the motor drive unit 11 to include a DC component. In a seventh embodiment of the present disclosure, the insulation resistance value calculation unit 15 acquires a DC component of a value corresponding to a command for one phase for causing the output voltage of the motor drive unit 11 to include a DC component. In an eighth embodiment of the present disclosure, the insulation resistance value calculation unit 15 acquires a DC component of a value corresponding to a command for each of three phases for causing the output voltage of the motor drive unit 11 to include a DC component.

[0110] The process of step S302 and the process of step S303 are executed at the same time.

[0111] In step S304, the insulation resistance value of the motor 3 is calculated.

[0112] <Configuration of Ninth Embodiment of Present Disclosure> In the ninth embodiment of the present disclosure, the insulation resistance value of the motor 3 is calculated using the DC component of the common mode current, which is the sum of the three-phase motor currents.

[0113] FIG. 11 is a circuit diagram showing a motor driving device according to a ninth embodiment of the present disclosure.

[0114] A motor drive device 1 according to a ninth embodiment of the present disclosure includes a converter 10, a motor drive unit 11, a control unit 12, a DC current detection unit 13, a DC voltage detection unit 14, an insulation resistance value calculation unit 15, a DC link capacitor 16, a clamp-type current probe 17, a U-phase shunt resistor 31U, a V-phase shunt resistor 31V, a W-phase shunt resistor 31W, and other circuits (not shown). Here, the other circuits may include, for example, a calculation processing unit, a storage device, a display device, an input device, a safety device, various sensors, and the like, but may also include other devices.

[0115] The converter 10, motor drive unit 11, control unit 12, DC voltage detection unit 14, DC link capacitor 16, U-phase shunt resistor 31U, V-phase shunt resistor 31V, and W-phase shunt resistor 31W are as described in the first embodiment. The AC power supply 2, motor 3, U-phase power line 51U, V-phase power line 51V, and W-phase power line 51W are as described in the first embodiment.

[0116] The U-phase power line 51U, the V-phase power line 51V, and the W-phase power line 51W are clamped by the clamps of the current probe 17. The clamp-type current probe 17 can detect the sum of the three-phase motor currents (common mode current) flowing through the U-phase power line 51U, the V-phase power line 51V, and the W-phase power line 51W.

[0117] A DC current detection unit 13 is connected to the current probe 17. The DC current detection unit 13 detects the DC component of the sum of the three-phase motor currents. The configuration of the DC current detection unit 13 is as described in the first embodiment. In particular, the sum of the three-phase motor currents (common mode current) flowing through the U-phase power line 51U, the V-phase power line 51V, and the W-phase power line 51W may contain noise components other than the DC component, so it is preferable to provide the DC current detection unit 13 with a low-pass filter 30. Alternatively, the DC current detection unit 13 may be configured as an analog circuit as described with reference to FIG. 3.

[0118] In the ninth embodiment of the present disclosure, the insulation resistance value calculation unit 15 calculates the DC component V of the output voltage detected by the DC voltage detection unit 14. d and the DC component I0 of the sum of the three-phase motor currents (common mode current) detected by the DC current detection unit 13, the resistance value R of the insulation resistor 20 of the motor 3 is calculated according to Equation 9. m Calculate.

[0119]

[0120] <Operation of Ninth Embodiment of Present Disclosure> FIG. 12 is a flowchart showing the operation flow of the process of calculating the insulation resistance value of the motor in the motor drive device according to the ninth embodiment of the present disclosure.

[0121] When the motor drive device 1 is operating, in step S401, the control unit 12 generates a command to cause the output voltage of each phase of the motor drive unit 11 to further include a DC component (to superimpose a DC component on the output voltage of each phase of the motor drive unit 11), and outputs the command to the motor drive unit 11.

[0122] In step S402, the DC current detection unit 13 detects the DC component of the sum of the three-phase motor currents.

[0123] In step S403, the DC voltage detector 14 detects the DC component of the output voltage of one phase.

[0124] The process of step S402 and the process of step S403 are executed at the same time.

[0125] In step S404, the insulation resistance value of the motor 3 is calculated.

[0126] <Modifications of the First, Second, Fourth, Fifth, and Seventh to Ninth Embodiments of the Present Disclosure> As described above, in the first, second, fourth, fifth, and seventh to ninth embodiments, the control unit 12 generates a command to cause the output voltage of each phase of the motor drive unit 11 to further include a DC component (to superimpose a DC component on the output voltage of each phase of the motor drive unit 11), and outputs the command to the motor drive unit 11. Therefore, the insulation resistance value of the motor 3 can be calculated even while the motor 3 is being rotated.

[0127] As a modification of this, the insulation resistance value of motor 3 may be calculated under a condition in which a command is output to cause motor driver 11 to include a DC component in the output voltage and to prevent the motor from rotating. For example, when motor driver 1 drives motor 3 installed in a machine tool, if control unit 12 outputs a command to cause motor driver 11 to include a DC component in the output voltage while motor 3 is rotating and the machine tool is performing a machining process, the machining accuracy of the machine tool may be affected. In this modification, control unit 12 outputs a command to generate a DC component superimposed on a command to excite motor 3 so as to prevent it from rotating. DC current detection unit 13 (or U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, and W-phase DC current detection unit 13W) detects the DC component of the motor current when control unit 12 outputs a command to motor driver 11 to cause motor driver 11 to include a DC component in the output voltage and to prevent motor 3 from rotating. Insulation resistance value calculation unit 15 calculates the insulation resistance value of motor 3 based on information related to the output voltage (the DC component of the output voltage or the DC component of a value corresponding to the command) when control unit 12 outputs a command to motor drive unit 11 to cause the output voltage of motor drive unit 11 to include a DC component and to prevent motor 3 from rotating, and based on the DC component of the motor current detected by DC current detection unit 13 (or U-phase DC current detection unit 13U, V-phase DC current detection unit 13V, and W-phase DC current detection unit 13W). This modification makes it possible to more reliably prevent a decrease in the machining accuracy of a machine tool equipped with motor drive device 1.

[0128] <Notification to Worker> The calculation result by the insulation resistance value calculation unit 15 may be notified to the worker by a notification unit (not shown) such as a display device, an audio device, or a printer. The worker can quickly and reliably grasp the insulation resistance value of the motor 3 based on the determination result based on the calculation result by the insulation resistance value calculation unit 15 that the worker has been notified of.

[0129] Examples of display devices include a standalone display monitor, a display monitor attached to the motor drive device 1, a display monitor attached to a higher-level control device (not shown) that controls the motor drive device 1, and a display monitor attached to a personal computer or mobile terminal.

[0130] The acoustic device may be, for example, a speaker that emits a sound indicating the insulation resistance value of the motor 3 .

[0131] The printer prints out the insulation resistance value of the motor 3 and the calculation date and time on paper or the like.

[0132] In addition, each time the insulation resistance value of the motor 3 is obtained, it may be stored in memory and accumulated, and by creating a database, it may be possible to use it for maintenance work, parts ordering work, etc.

[0133] <Processor and Memory> The motor drive device 1 is provided with at least one processor, which is an arithmetic processing device. Examples of arithmetic processing devices include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing device includes a control unit 12, an insulation resistance value calculation unit 15, and other processing units. These units of the arithmetic processing device are functional modules implemented by programs executed on the processor. For example, if the control unit 12, the insulation resistance value calculation unit 15, and other processing units are implemented in the form of programs, the functions of each unit can be realized by operating the arithmetic processing device in accordance with the programs. The programs for executing the processes in the control unit 12, the insulation resistance value calculation unit 15, and other processing units may be provided in the form of being recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the control unit 12, the insulation resistance value calculation unit 15, and other processing units may be implemented as semiconductor integrated circuits on which programs for implementing the functions of each unit are written.

[0134] The motor drive device 1 also includes at least one memory serving as a storage device. The memory includes the control unit 12, the insulation resistance value calculation unit 15, and various storage units within the other processing units. Examples of the memory include electrically erasable and recordable nonvolatile memory such as EEPROM (registered trademark), or high-speed read / write random access memory such as DRAM or SRAM. The storage unit may also include a hard disk drive (HDD) or solid state drive (SSD). The memory stores programs for operating the control unit 12, the insulation resistance value calculation unit 15, and the other processing units. The memory also stores data related to the DC component of the motor current detected by the DC current detection unit 13, the U-phase DC current detection unit 13U, the V-phase DC current detection unit 13V, and the W-phase DC current detection unit 13W. The memory stores data relating to the DC components of the output voltages detected by the DC voltage detection unit 14, the U-phase DC voltage detection unit 14U, the V-phase DC voltage detection unit 14V, and the W-phase DC voltage detection unit 14W. The memory stores data relating to the DC components of values ​​corresponding to commands. The memory stores data relating to the insulation resistance value of the motor 3 calculated by the insulation resistance value calculation unit 15. The memory stores various programs and data relating to the control unit 12. The memory stores various programs and data relating to the motor drive device 1.

[0135] Advantages of the Embodiments and Modifications of the Present Disclosure According to the first to ninth embodiments and their modifications of the present disclosure, the insulation resistance value of a motor can be easily and accurately calculated even while the motor is being driven by a motor drive device. Furthermore, according to the second and fifth embodiments and their modifications of the present disclosure, the offset of the DC current detection unit is canceled, thereby enabling more accurate calculation of the motor's insulation resistance value. Furthermore, according to the fourth to sixth embodiments and their modifications of the present disclosure, the insulation resistance value of a motor can be more accurately calculated even when the motor current is unbalanced among the three phases or the output voltage of the motor drive unit is unbalanced among the three phases.

[0136] In a conventional method for detecting motor insulation deterioration, the AC power supply is disconnected from the motor drive device, and the DC voltage of the DC link capacitor is applied to the motor, and the output voltage is detected to calculate the insulation resistance value. However, disconnecting the AC power supply from the motor drive device every time the motor's insulation resistance value is calculated is time-consuming and inefficient. Furthermore, the need to install an electromagnetic contactor to disconnect the AC power supply from the motor drive device increases costs. Furthermore, the method of calculating the insulation resistance value by disconnecting the AC power supply from the motor drive device is not applicable to motor drive devices that use fuses instead of electromagnetic contactors. In particular, for machine tools, disconnecting the AC power supply from the motor drive device and stopping the motor just to calculate the motor's insulation resistance value is inefficient. Furthermore, because machine tools are not often stopped, deterioration of the motor's insulation resistance is difficult to notice.

[0137] In contrast, according to the first to ninth embodiments and their modifications of the present disclosure, the insulation resistance value of a motor can be easily calculated in real time without disconnecting the motor drive device from the AC power supply and without stopping the drive of the motor by the motor drive device. Therefore, an operator can quickly and reliably grasp the insulation resistance value of the motor, which is also effective for preventive maintenance. For example, in a machine tool, it is not necessary to disconnect the AC power supply from the motor drive device and stop the drive of the motor just to calculate the insulation resistance value of the motor. Furthermore, the first to ninth embodiments and their modifications of the present disclosure can also be applied to a motor drive device that uses a fuse instead of an electromagnetic contactor.

[0138] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments and individual variations described above. Various additions, substitutions, modifications, partial deletions, etc. are possible for these embodiments and variations within the scope of the gist of the present disclosure, or within the scope of the gist of the present disclosure derived from the content of the claims and their equivalents. These embodiments and variations can also be implemented in combination. For example, in the above-described embodiments and variations, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical formulas are used in the description of the above-described embodiments and variations.

[0139] <Supplementary Notes> The following supplementary notes are further disclosed regarding the above-described embodiment and modifications.

[0140] (Supplementary Note 1) A motor drive device comprising: a motor drive unit that supplies a three-phase motor current to the motor by applying a three-phase output voltage to the motor; a control unit that outputs a command to the motor drive unit to control the output voltage of the motor drive unit; a DC current detection unit that detects a DC component of the motor current when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component; and an insulation resistance value calculation unit that calculates an insulation resistance value of the motor based on information related to the output voltage when the control unit outputs the command to the motor drive unit and the DC component of the motor current detected by the DC current detection unit. (Supplementary Note 2) The motor drive device according to Supplementary Note 1, further comprising: a DC voltage detection unit that detects the DC component of the output voltage of the motor drive unit as information related to the output voltage, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the output voltage detected by the DC voltage detection unit and the DC component of the motor current detected by the DC current detection unit. (Note 3) A DC voltage detection unit is provided to detect the DC component of the output voltage of one phase of the motor drive unit as information related to the output voltage, and the DC current detection unit detects the DC component of the motor current of one phase, and the DC component of the motor current detected by the DC current detection unit is calculated as I d and the DC component of the output voltage detected by the DC voltage detection unit is V dWhen this is done, the insulation resistance value calculation unit calculates the motor insulation resistance value R m of, The motor drive device according to claim 2, further comprising a DC voltage detection unit that detects DC components of the three-phase output voltage of the motor drive unit as information related to the output voltage, the DC current detection unit detects DC components of the three-phase motor current, and calculates the DC components of the motor current of each of the three phases detected by the DC current detection unit based on I. du , I dv and I dw The DC component of the output voltage of each of the three phases detected by the DC voltage detection unit is V du , V dv and V dw When this is done, the insulation resistance value calculation unit calculates the motor insulation resistance value R m of, (Supplementary Note 5) The motor drive device according to Supplementary Note 2, wherein the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC components of the multiple output voltages detected by the DC voltage detection unit and the DC components of the multiple motor currents detected by the DC current detection unit. (Supplementary Note 6) The DC current detection unit detects the DC component of the motor current of one phase, and the DC voltage detection unit detects the DC component of the output voltage of one phase, and the DC component of the motor current detected by the DC current detection unit is calculated as I at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component. d1 The DC component of the output voltage detected by the DC voltage detection unit at the first timing is V d1 and the DC component of the motor current detected by the DC current detection unit at the second timing when the control unit outputs a command to the motor drive unit to include a DC component in the output voltage is defined as I d2 The DC component of the output voltage detected by the DC voltage detection unit at the second timing is V d2 When this is done, the insulation resistance value calculation unit calculates the motor insulation resistance value R m of, The motor drive device according to claim 5, wherein the DC current detection unit detects DC components of the three-phase motor currents, the DC voltage detection unit detects DC components of the three-phase output voltages, and the DC components of the motor currents of the three phases detected by the DC current detection unit at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component are calculated based on I. du1 , I dv1 and I dw1 The DC component of the output voltage of each of the three phases detected by the DC voltage detection unit at the first timing is V du1 , V dv1 and V dw1 The DC components of the motor currents of the three phases detected by the DC current detection unit at the second timing when the control unit outputs a command to the motor drive unit to include a DC component in the output voltage are defined as I du2 , I dv2 and I dw2 The DC component of the output voltage of each of the three phases detected by the DC voltage detection unit at the second timing is V du2 , V dv2 and V dw2 When this is done, the insulation resistance value calculation unit calculates the motor insulation resistance value R m of, (Supplementary Note 8) The motor drive device according to Supplementary Note 1, wherein the information relating to the output voltage is a DC component of a value corresponding to a command to cause the output voltage to include a DC component, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the value corresponding to the command and the DC component of the motor current detected by the DC current detection unit. (Supplementary Note 9) The motor drive device according to Supplementary Note 1, wherein the information relating to the output voltage is a DC component of a value corresponding to a command to cause the output voltage to include a DC component, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the value corresponding to the command and the DC component of the motor current detected by the DC current detection unit. d The DC component of the value corresponding to the command is V d * When this is the case, the insulation resistance value calculation unit calculates the motor insulation resistance value Rm as follows: The motor drive device according to claim 8, wherein the DC component of the motor current detected by the DC current detection unit at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is calculated based on I. d1and the DC component of the value corresponding to the command at the first timing is V d1 * and the DC component of the motor current detected by the DC current detection unit at the second timing when the control unit outputs a command to the motor drive unit to include a DC component in the output voltage is defined as I d2 and the DC component of the value corresponding to the command at the second timing is V d2 * When this is the case, the insulation resistance value calculation unit calculates the motor insulation resistance value Rm as follows: The motor drive device according to claim 8, wherein the DC components of the motor currents of the three phases detected by the DC current detection unit are calculated based on I du , I dv and I dw The DC component of the value corresponding to the command for each of the three phases is V du * , V dv * and V dw * When this is the case, the insulation resistance value calculation unit calculates the motor insulation resistance value Rm as follows: The motor drive device according to claim 8, wherein the DC components of the motor currents of the three phases detected by the DC current detection unit at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component are calculated based on I. du1 , I dv1 and I dw1 The DC component of the value corresponding to the command for each of the three phases at the first timing is V du1 * , V dv1 * and V dw1 * The DC components of the motor currents of the three phases detected by the DC current detection unit at the second timing when the control unit outputs a command to the motor drive unit to include a DC component in the output voltage are defined as I du2 , I dv2 and I dw2 The DC component of the value corresponding to the command for each of the three phases at the second timing is V du2 * , V dv2 * and Vdw2 * When this is the case, the insulation resistance value calculation unit calculates the motor insulation resistance value Rm as follows: (Supplementary Note 13) The motor drive device according to Supplementary Note 1, further comprising a DC voltage detection unit that detects a DC component of the output voltage of the motor drive unit as information related to the output voltage, the DC current detection unit detects the DC component of the sum of the motor currents of three phases, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the output voltage detected by the DC voltage detection unit and the DC component of the sum of the motor currents of three phases detected by the DC current detection unit. (Supplementary Note 14) The motor drive device according to any one of Supplementary Notes 1 to 13, wherein the DC current detection unit detects the DC component of the motor current when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component and to prevent the motor from rotating, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on information related to the output voltage when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component and to prevent the motor from rotating, and on the DC component of the motor current detected by the DC current detection unit.

[0141] REFERENCE SIGNS LIST 1 Motor drive device 2 AC power supply 3 Motor 10 Converter 11 Motor drive unit 11U U-phase AC voltage source 11V V-phase AC voltage source 11W W-phase AC voltage source 12 Control unit 13 DC current detection unit 13U U-phase DC current detection unit 13V V-phase DC current detection unit 13W W-phase DC current detection unit 14 DC voltage detection unit 14U U-phase DC voltage detection unit 14V V-phase DC voltage detection unit 14W W-phase DC voltage detection unit 15 Insulation resistance value calculation unit 16 DC link capacitor 17 Current probe 30 Low-pass filter 31U U-phase shunt resistor 31V V-phase shunt resistor 31W W-phase shunt resistor 32, 33 Filter resistor 34 Filter capacitor 35 Amplification circuit 36 ​​AD converter 40 Low-pass filter 41 Filter resistor 42 Filter capacitor 43 Amplifier circuit 44 AD converter 51U U-phase power line 51V V-phase power line 51W W-phase power line

Claims

1. A motor drive device comprising: a motor drive unit that supplies a three-phase motor current to a motor by applying a three-phase output voltage to the motor; a control unit that outputs a command to the motor drive unit to control the output voltage of the motor drive unit; a DC current detection unit that detects the DC component of the motor current when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component; and an insulation resistance value calculation unit that calculates the insulation resistance value of the motor based on information related to the output voltage when the control unit outputs the command to the motor drive unit and the DC component of the motor current detected by the DC current detection unit.

2. A motor drive device as described in claim 1, further comprising a DC voltage detection unit that detects the DC component of the output voltage of the motor drive unit as information related to the output voltage, and wherein the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the output voltage detected by the DC voltage detection unit and the DC component of the motor current detected by the DC current detection unit.

3. A DC voltage detection unit is provided which detects a DC component of the output voltage of one phase of the motor drive unit as information related to the output voltage, and the DC current detection unit detects a DC component of the motor current of the one phase, and the DC component of the motor current detected by the DC current detection unit is expressed as I d and the DC component of the output voltage detected by the DC voltage detection unit is V d When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 2 , wherein the calculation is based on the following formula:

4. A DC voltage detection unit is provided to detect DC components of the output voltages of the three phases of the motor drive unit as information related to the output voltage, and the DC current detection unit detects DC components of the motor currents of the three phases, and the DC components of the motor currents of the three phases detected by the DC current detection unit are expressed as I du , I dv and I dw and the DC component of the output voltage of each of the three phases detected by the DC voltage detection unit is V du , V dv and V dw When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 2 , wherein the calculation is based on the following formula:

5. A motor drive device as described in claim 2, wherein the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC components of the multiple output voltages detected by the DC voltage detection unit and the DC components of the multiple motor currents detected by the DC current detection unit.

6. The DC current detection unit detects the DC component of the motor current of one phase, and the DC voltage detection unit detects the DC component of the output voltage of the one phase, and the DC component of the motor current detected by the DC current detection unit is designated as I at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component. d1 the DC component of the output voltage detected by the DC voltage detection unit at the first timing is V d1 and the DC component of the motor current detected by the DC current detection unit at a second timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is defined as I. d2 and the DC component of the output voltage detected by the DC voltage detection unit at the second timing is V d2 When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 5, wherein the calculation is based on the following formula:

7. The DC current detection unit detects the DC component of the three-phase motor current, and the DC voltage detection unit detects the DC component of the three-phase output voltage, and the DC component of the motor current of each of the three phases detected by the DC current detection unit is calculated as I at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component. du1 , I dv1 and I dw1 and the DC component of the output voltage of each of the three phases detected by the DC voltage detection unit at the first timing is V du1 , V dv1 and V dw1 and the DC component of the motor current of each of the three phases detected by the DC current detection unit at a second timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is defined as I du2 , I dv2 and I dw2 and the DC component of the output voltage of each of the three phases detected by the DC voltage detection unit at the second timing is V du2 , V dv2 and V dw2 When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 5, wherein the calculation is based on the following formula:

8. A motor drive device as described in claim 1, wherein the information related to the output voltage is a DC component of a value corresponding to the command that causes the output voltage to include a DC component, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the value corresponding to the command and the DC component of the motor current detected by the DC current detection unit.

9. The DC component of the motor current detected by the DC current detection unit is expressed as I d and the DC component of the value corresponding to the command is V d * When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 8, wherein the calculation is based on the following formula:

10. The DC component of the motor current detected by the DC current detection unit at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is calculated as I. d1 and the DC component of the value corresponding to the command at the first timing is V d1 * and the DC component of the motor current detected by the DC current detection unit at a second timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is defined as I. d2 and the DC component of the value corresponding to the command at the second timing is V d2 * When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 8, wherein the calculation is based on the following formula:

11. The DC component of the motor current of each of the three phases detected by the DC current detection unit is expressed as I du , I dv and I dw and the DC component of the value corresponding to the command for each of the three phases is V du * , V dv * and V dw * When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 8, wherein the calculation is based on the following formula:

12. The DC component of the motor current of each of the three phases detected by the DC current detection unit at a first timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is calculated as I. du1 , I dv1 and I dw1 and the DC component of the value corresponding to the command for each of the three phases at the first timing is V du1 * , V dv1 * and V dw1 * and the DC component of the motor current of each of the three phases detected by the DC current detection unit at a second timing when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component is defined as I du2 , I dv2 and I dw2 and the DC component of the value corresponding to the command for each of the three phases at the second timing is V du2 * , V dv2 * and V dw2 * When the insulation resistance value calculation unit calculates the insulation resistance value R of the motor. m of, The motor drive device according to claim 8, wherein the calculation is based on the following formula:

13. The motor drive device according to claim 1, further comprising a DC voltage detection unit that detects a DC component of the output voltage of the motor drive unit as information related to the output voltage, wherein the DC current detection unit detects the DC component of the sum of the motor currents of three phases, and wherein the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on the DC component of the output voltage detected by the DC voltage detection unit and the DC component of the sum of the motor currents of three phases detected by the DC current detection unit.

14. A motor drive device according to any one of claims 1 to 13, wherein the DC current detection unit detects the DC component of the motor current when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component and to prevent the motor from rotating, and the insulation resistance value calculation unit calculates the insulation resistance value of the motor based on information related to the output voltage when the control unit outputs a command to the motor drive unit to cause the output voltage to include a DC component and to prevent the motor from rotating, and on the DC component of the motor current detected by the DC current detection unit.

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