TWI851837B - Motor control device and insulation resistance detection method of same - Google Patents

Abstract

A motor control device includes a second switch capable of connecting a negative bus to ground, a third switch of which one end is connected to a second power source section connected to the bus and of which other end is connectable to ground, a current detection section configured to detect a current value between a coil of a motor and the negative bus, and an insulation resistance calculation section configured to calculate an insulation resistance value of the motor based on current values detected by the current detection section when the third switch is opened and when the third switch is closed in a state in which the charge of a grounding capacitor is discharged in such a manner that a power supply is turned off by a first switch and the second switch is turned on for predetermined time, a voltage value of a capacitor, and a voltage value of the second power source section.

Description

Motor control device and insulation resistance detection method thereof

One aspect of the present disclosure is related to a motor control device and an insulation resistance detection method of the motor control device.

Motors such as servomotors are driven by motor control devices including inverters and are widely used in machine tools. In machines such as machine tools that use cutting fluid for processing, the cutting fluid adheres to the motor. The cutting fluid may enter the motor and deteriorate the insulation of the motor.

Furthermore, when the motor is used in a device other than a working machine, when it is used for a long period of time, or when it is used in a harsh environment, the insulation of the motor may deteriorate.

The insulation of the motor deteriorates gradually, and eventually the motor will have a ground fault. If the motor has a ground fault, the leakage circuit breaker will trip or the motor control device will be damaged. As a result, the system will shut down. The system shutdown will have a significant impact on the factory's production line. Therefore, from the perspective of preventive maintenance, it is desirable to have a device that can detect the insulation resistance of the motor.

Such a method for detecting the insulation resistance of a motor is described, for example, in Japanese Patent Gazette No. 2015-129704. The motor drive device described in Japanese Patent Gazette No. 2015-129704 has a rectifier circuit, a power supply unit, an inverter unit, a current detection unit, a second switch, and an insulation resistance detection unit. The rectifier circuit rectifies the AC voltage supplied from the AC power supply through the first switch into a DC voltage. The power supply unit smoothes the DC voltage rectified by the rectifier circuit by a capacitor. The inverter unit converts the DC voltage smoothed by the power supply unit into an AC voltage by switching the semiconductor switching element. The inverter unit drives the motor via the AC voltage. The current detection unit measures the current value flowing through a resistor whose one end is connected to the motor coil and the other end is connected to one of the capacitor terminals. The voltage detection unit measures the voltage values at both ends of the capacitor. The second switch grounds the other terminal of the capacitor. The insulation resistance detection unit detects the resistance between the motor coil and the ground, that is, the insulation resistance value of the motor, using two sets of current values and voltage values measured in two states: stopping the operation of the motor and disconnecting (off) the first switch and disconnecting the second switch, and turning on (on).

In the technology of Japanese Patent Publication No. 2015-129704, the insulation resistance of the motor is calculated from two sets of measurement results using the voltage of the smoothing capacitor. In this calculation, the equivalent resistance corresponding to the leakage current of each semiconductor switching element is eliminated. In this way, the influence of the leakage current of the semiconductor switching element is eliminated.

According to the circuit structure described in the Japanese Patent Publication No. 2015-129704, in the above two states, when the first switch is disconnected and the second switch is disconnected, the potential difference between the negative bus of the smoothing capacitor and the ground is 0V, and no current flows through the insulation resistance of the motor. Therefore, the equivalent resistance equivalent to the leakage current of the semiconductor switching element can be accurately calculated.

A motor control device comprises: a first power supply unit; a first switch, which can disconnect the power supply from the first power supply unit; a DC supply unit, which outputs the power from the first power supply unit to a bus; a capacitor, which is connected to the bus; a switching element, which converts the DC voltage supplied to the bus into an AC voltage, and drives and controls the motor with the AC voltage; a grounding capacitor, which is connected to the negative bus; a second switch, which can ground the negative bus; and a third switch, one end of which is connected to the second power supply unit connected to the bus. a current detecting unit for detecting a current value between the winding of the motor and the negative bus bar; and an insulation resistance calculating unit for calculating the insulation resistance value of the motor based on the current values detected by the current detecting unit, the voltage value of the capacitor, and the voltage value of the second power supply unit when the third switch is turned on and the third switch is turned off, respectively, when the power supply is cut off via the first switch, the second switch is turned on for a specified time, and the charge of the grounded capacitor is discharged.

In the following detailed description, for the purpose of explanation, many specific details are mentioned in order to provide a deeper understanding of the disclosed embodiments. However, it should be understood that one or more embodiments may be implemented without these specific details. In other different cases, well-known structures and devices are schematically shown to simplify the drawings.

However, in actual motor control devices, in most cases, a grounding capacitor is inserted between the negative bus of the smoothing capacitor and the ground for interference prevention. Moreover, in a three-phase AC power supply, the S phase or the neutral point is usually grounded. In such a configuration, when the method for detecting the insulation resistance of the motor described in Japanese Patent Gazette No. 2015-129704 is applied, the first switch is turned on and the AC power is supplied, and a potential difference is generated between the negative bus of the smoothing capacitor and the ground at the frequency of the AC power supply through the rectifier circuit. For this reason, the grounding capacitor is charged due to its potential difference. Next, when the first switch is disconnected to measure the insulation resistance of the motor, if the voltage of the grounding capacitor remains, in the current detection unit, not only the leakage current of the semiconductor switching element due to the voltage of the smoothing capacitor, but also the current flowing through the insulation resistance of the motor due to the voltage of the grounding capacitor. Therefore, it is difficult to accurately calculate the equivalent resistance equivalent to the leakage current of the semiconductor switching element.

One object of the present disclosure is to provide a motor control device having a grounding capacitor inserted between a negative bus bar and ground, which can accurately detect the insulation resistance of the motor.

The motor control device described in one form of the present disclosure comprises: a first power supply unit; a first switch, which can disconnect the power supply from the first power supply unit; a DC supply unit, which outputs the power from the first power supply unit to the bus; a capacitor, which is connected to the bus; a switching element, which converts the DC voltage supplied to the bus into an AC voltage, and uses the AC voltage to drive and control the motor; a grounding capacitor, which is connected to the negative bus; a second switch, which can ground the negative bus; a third switch, one end of which is connected to the front The first switch is connected to the second power supply unit of the bus bar, and the other end can be grounded; a current detection unit detects the current value between the winding of the motor and the negative bus bar; and an insulation resistance calculation unit calculates the insulation resistance value of the motor based on the current value detected by the current detection unit, the voltage value of the capacitor, and the voltage value of the second power supply unit when the third switch is turned on and the third switch is turned off, respectively, when the power supply is cut off through the first switch, and the second switch is turned on for a specified time, so that the charge of the grounded capacitor is discharged.

Another form of the present disclosure is a method for detecting the insulation resistance of a motor control device. The motor control device comprises: a first power supply unit; a first switch that can disconnect the power supply from the first power supply unit; a DC supply unit that outputs the power from the first power supply unit to a bus; a capacitor that is connected to the bus; a switching element that converts the DC voltage supplied to the bus into an AC voltage and uses the AC voltage to drive and control the motor; and a grounding capacitor that is connected to the negative bus. The method for detecting the insulation resistance of the motor control device comprises: a process of disconnecting the power supply through the first switch; a process of grounding the negative bus through the second switch that can ground the negative bus. The process of conducting for a predetermined time to discharge the charge of the grounded capacitor; the process of setting the aforementioned third switch of the second power supply unit, one end of which is connected to the aforementioned bus and the other end of which can be grounded through the third switch, to open, and using the current detection unit to detect the first current value between the winding of the motor and the aforementioned bus connected to the aforementioned second power supply unit; the process of setting the aforementioned third switch to close, and using the aforementioned current detection unit to detect the second current value between the winding of the motor and the aforementioned bus connected to the aforementioned second power supply unit; and the process of calculating the insulation resistance value of the aforementioned motor based on the detected first current value and the aforementioned second current value, the voltage value of the aforementioned capacitor and the voltage value of the aforementioned second power supply unit.

Other aspects of the present disclosure will become apparent from the following description of embodiments for implementing the disclosed aspects.

According to the disclosed form, the power supply from the first power source unit is stopped by disconnecting the power supply using the first switch unit. Then, while calculating the insulation resistance value of the motor, the second switch is turned on before the third switch is turned off while the power supply from the first power source unit is stopped. As a result, the charge stored in the grounding capacitor connected to the negative bus is discharged to the ground side. As a result, there is no potential difference between the negative bus and each grounding point.

When the third switch is turned on in this state, a leakage current flows through the switching element due to the voltage of the capacitor, and the first current value is detected by the current detection unit. On the other hand, when the third switch is turned off in a state where the power supply from the first power source unit is stopped, the current detection unit detects the first current value and a second current value including most of the current flowing through the winding of the motor due to the voltage of the second power source unit (the remainder is a small leakage current of the switching element on the negative side). By performing calculation based on two current values detected by the current detection unit, that is, the first current value and the second current value, and the voltage value of the capacitor and the voltage value of the second power supply unit, the insulation resistance value of the motor can be calculated with good accuracy.

Furthermore, here, the "first switch" includes all switches including a circuit breaker. The "first switch" includes any switch that has a terminal or contact that can disconnect the power supply from the power source even if it is in contact with the terminal of a battery or a power source. Moreover, as a "DC supply unit", a power converter that converts AC power into DC power can be used. Others referred to as "switches" include the aforementioned "first switch". The "switch" may be any switch as long as it can stop or flow current. The "switch" also includes mechanical switches, relays, and semiconductor switches.

As described above, according to the aspect of the present disclosure, a motor control device can be provided, which is a motor control device in which a grounding capacitor is inserted between a negative bus bar and a ground, and can accurately detect the insulation resistance of the motor.

FIG1 shows the first aspect of the present disclosure.

Furthermore, in the following description, current may include current value, voltage may include voltage value, resistance may include resistance value, and resistance may include resistance value. These terms are to be interpreted according to the technical common sense of a person having ordinary knowledge in the relevant technical field.

The motor control device _Cont1 includes a rectifier circuit (DC supply unit) S _DC , a bus ML including a positive bus ML _{+ and} a negative bus ML-, smoothing capacitors (capacitors) C ₁ , C ₂ , an inverter including semiconductor switching elements TR ₁ to TR ₆ , and an insulation resistance calculation unit 3 ₁ .

The motor control device _Cont1 is supplied with three-phase AC voltage from the three-phase AC power source (first power source) _S1 through the first switch that can cut off the power supply, that is, the electromagnetic contactor MS. The motor control device _Cont1 generates a DC voltage by full-wave rectifying the three-phase AC voltage using a rectifier circuit (DC supply unit) _SDC , and outputs the DC voltage to the bus ML.

The output DC voltage is smoothed by smoothing capacitors (capacitors) C ₁ , C ₂ connected between the bus ML ₊ on the positive side and the bus _ML- on the negative side of the bus ML.

The smoothed DC voltage supplied to the buses ML ₊ and _ML- is supplied to an inverter including semiconductor switching elements _TR1 to _TR6 connected between the positive bus ML ₊ and the negative bus _ML- . The AC voltage obtained by inverting the DC voltage supplied to the buses ML ₊ and _ML- drives the motor 1.

The motor control device _Cont2 includes a bus ML including a positive bus ML ₊ and a negative bus _ML- , a smoothing capacitor (capacitor) _C2 , an inverter including semiconductor switching elements _TR7 to _TR12 , and an insulation resistance calculation unit ₃₂ .

Motor control device _Cont2 is supplied with a DC voltage from the rectifier circuit S _DC of motor control device _Cont1 . Motor control device _Cont2 is configured to drive motor 2 with an AC voltage obtained by inverting the DC voltage supplied to bus ML using an inverter including semiconductor switching elements TR ₇ to TR ₁₂ .

The negative busbars _ML- of the motor control devices _Cont1 and _Cont2 are grounded through grounding capacitors _C3 and _C4 respectively for anti-interference.

Here, further, a grounding switch, that is, a second switch SW ₁ is provided on the negative-side bus ML ₋ .

In this form, it is indicated that it is applicable to a two-axis drive configuration in which motor 1 and motor 2 drive their own axes respectively.

The insulation resistance calculation unit ₃₁ of the motor control device _Cont1 includes: a DC power supply unit provided between the negative bus _ML- in the bus ML and the ground E, that is, a DC power supply (second power supply unit) _S2 , a third switch _SW2 (third switch), a current detection resistor _R1 connecting the negative bus _ML- and the winding L of the motor 1, and a detection control unit (current detection unit) _41. The second switch _SW1 and the third switch _SW2 are connected in series starting from the negative bus _ML- in this order. One end of the DC power supply _S2 is connected to _ML- , and the other end can be grounded through the third switch _SW2 . The detection control unit ₄₁ detects the current from the voltage of the current detection resistor _R1 . Furthermore, the detection control unit ₄₁ controls the detection operation of the insulation resistance and calculates the insulation resistance value.

The insulation resistance calculation unit ₃₂ of the motor control device _Cont2 includes: a current detection resistor _R2 connecting the negative bus _ML- of the bus ML and the winding L of the motor 2, and a detection control unit (current detection unit) _42. The detection control unit ₄₂ detects the current from the voltage of the current detection resistor _R2 . Furthermore, the detection control unit ₄₂ calculates the insulation resistance value.

The current detection resistors _R1 and _R2 are connected to the winding L of one of the U phase, V phase, and W phase of the motors 1 and 2 of their respective shafts. Since the resistance of the winding L of the motors 1 and 2 is very small, detection can be performed in any phase.

The power source used as the DC power source _S2 is a power source with a voltage as high as possible within a voltage range lower than the voltage of the smoothing capacitors _C1 and _C2 , that is, a power source set so that the potential on the ground E side is higher than the negative bus _ML- . Furthermore, as the DC power source _S2 , a power source with a small current capacity required for measurement is used.

The reason why the voltage of the DC power source _S2 is set lower than the voltage of the smoothing capacitors _C1 and _C2 is as follows. That is, the reason is to suppress the current from flowing from the insulating resistors _Rm1 and _Rm2 of the motors 1 and 2 through the flywheel diodes _Df of the semiconductor switching elements _TR1 to _TR3 and _TR7 to _TR9 of the upper arm (positive side) of the inverter section to charge the smoothing capacitors _C1 and _C2 during measurement, and to suppress the detection accuracy of the insulating resistors _Rm1 and _Rm2 from decreasing.

The operation of the aforementioned motor control devices _Cont1 and _Cont2 is described below.

In normal motor control, the second switch _SW1 and the third switch _SW2 are kept OFF, and the electromagnetic contactor MS is turned ON. As a result, the motor of each axis is controlled via the inverter. During insulation resistance detection, the motor control devices _Cont1 and _Cont2 operate as follows.

Stop the motor control operation of all axes, disconnect the semiconductor switching elements TR ₁ to TR ₁₂ , and cut off the electromagnetic contactor MS. Then, keep the third switch SW ₂ off and turn on the second switch SW _1. During the specified time, discharge the charges of the grounding capacitors C ₃ and C ₄ , and make the potential difference between the negative bus and the ground 0V. Then, disconnect the second switch SW ₁ , measure the DC voltage V _PN of the inverter, the voltage _VR1A of the current detection resistor R ₁ , and the voltage _VR2A of the current detection resistor R ₂ .

Since the voltage of the grounded capacitors _C3 and _C4 is 0V, no current flows from the grounded capacitors _C3 and _C4 to the measurement circuit through the insulating resistors _Rm1 and _Rm2 of the motors 1 and 2.

The voltage of the smoothing capacitors _C1 and _C2 is applied to the semiconductor switching elements _TR1 to _TR12 constituting the inverter. Therefore, the DC voltage _VPN of the inverter is substantially equal to the voltage of the smoothing capacitors _C1 and _C2 . Through the voltage, a current flows from the semiconductor switching element _TR1 to _TR4 , and a current (first current (value)) flows through the current detection resistor _R1 . Similarly, a current flows from the semiconductor switching element _TR7 to _TR10 , and a current (first current (value)) flows through the current detection resistor _R2 .

The current flowing from the semiconductor switching element _TR1 to _TR4 on the positive side and the current flowing from the semiconductor switching element _TR7 to _TR10 are leakage currents of the semiconductor switching elements. The leakage currents flow in all phases in the same way. By focusing on one phase connected with the current detection resistors _R1 and _R2 , the insulation resistance of the motor can be obtained.

When the equivalent leakage resistance of the semiconductor switching elements TR ₁ and TR ₄ is determined to be R _tr1 , and the equivalent leakage resistance of the semiconductor switching elements TR ₇ and TR ₁₀ is determined to be R _tr2 , the following equations (1) and (2) are established.

Next, the third switch SW ₂ is turned on, and the voltage V _DC of the DC power source S ₂ is applied between the negative bus _ML- and the ground E. In this state, the voltage _VR1B of the current detection resistor _R1 and the voltage _VR2B of the current detection resistor _R2 are measured. From these current detection resistors _R1 and _R2 and the voltages _VR1B and _VR2B , the current (second current (value)) flowing through the current detection resistors _R1 and _R2 can be obtained.

When the insulation of the motor 1 is degraded, the voltage of the DC power source _S2 is applied to the semiconductor switching element TR ₄ through the insulating resistor R _m1 of the motor. As a result, a current flows through the current detection resistor R ₁ and the semiconductor switching element TR ₄ .

Similarly, when the insulation of the motor 2 is degraded, the voltage of the DC power source _S2 is applied to the semiconductor switching element _TR10 through the insulating resistor _Rm2 of the motor. Therefore, a current flows through the current detection resistor _R2 and the semiconductor switching element _TR10 .

Then, the voltage of the smoothing capacitors C ₁ and C ₂ , that is, the DC voltage V _PN of the inverter, is applied to the semiconductor switching elements TR ₁ and TR ₄ . Therefore, a current flows from the semiconductor switching element TR ₁ to TR ₄ . Furthermore, a current also flows through the current detection resistor R ₁ .

Similarly, current flows from the semiconductor switching element _TR7 to _TR10 . Furthermore, current also flows through the current detection resistor _R2 .

The current flowing from the semiconductor switching element _TR1 to _TR4 and the current flowing from the semiconductor switching element _TR7 to _TR10 are leakage currents of these semiconductor switching elements. However, the leakage current of these semiconductor switching elements is generally smaller than the current flowing due to the decrease in the insulation resistance of the motor. Therefore, it can be assumed that the voltage of the smoothing capacitors _C1 and _C2 will hardly drop even if there is leakage current.

At this time, the following equations (3) and (4) are established.

The insulation resistance R _m1 of the motor 1 can be obtained by solving the simultaneous equations of the above equations (1) and (3) and by the following equation (5).

Furthermore, the insulation resistance R _m2 of the motor 2 can be obtained by solving the simultaneous equations of the above-mentioned equations (2) and (4) and by using the following equation (6).

These calculations are performed by the detection control units ₄₁ and _42. Of course, the insulation resistance values Rm1 and Rm2 can be calculated by detecting the voltages _VR1A and _VR2A of the current detection resistors R1 and _{R2 one by one. In this regard, either or both of the two voltages VR1A and VR2A can be measured} multiple times, _{and the insulation resistance values Rm1 and Rm2 can be calculated} by using various average values of the measured voltages.

When such various average values are used, the influence of abnormal values due to interference or the like can be reduced, and more accurate insulation resistance values R _m1 and R _m2 can be obtained.

Next, the calculated insulation resistance values R _m1 and R _m2 are transmitted as information to the user device. The insulation resistance values R _m1 and R _m2 may be transmitted by any means. The means for transmitting the insulation resistance values R _m1 and R _m2 may be wired transmission or wireless transmission.

The user who knows the insulation resistance values R _m1 and R _m2 can judge the insulation resistance degradation when the insulation resistance value is low, and predict the motor ground fault and system shutdown in advance. Therefore, the user can prevent such inconvenience from occurring by taking preventive measures such as replacing the motor in advance.

In determining whether the insulation resistance has deteriorated, an appropriate determination method may be used. For example, the determination method may be a method of comparing with a value learned experimentally or empirically, a method of comparing with an initial value measured and recorded or memorized using a normal product when the motor control device is initially set up, or a method of comparing with other set values of a safety standard.

The insulation resistance _Rm1 and _Rm2 of the motors 1 and 2 are very small, and the semiconductor switching elements _TR4 to _TR6 and _TR10 to _TR12 on the negative side of the semiconductor switching elements TR1 to _TR12 may be short-circuited and damaged. In this case, the current flows from the DC power source _S2 to the semiconductor switching elements _TR4 to _TR6 and _TR10 to _TR12 on the negative side through the insulation deterioration portion of the motors ₁ and 2. Here, the current capacity of the DC power source _S2 can be very small compared to the smoothing capacitors _C1 and _C2 . Therefore, the flowing current can be limited to a small current.

Therefore, the possibility of secondary damage to the negative-side semiconductor switching elements TR ₄ to TR ₆ and TR ₁₀ to TR ₁₂ and further insulation degradation of the motors 1 and 2 is low.

In the above-mentioned form, the case where the embodiment of the present disclosure is applied to a motor control device with two axes using two motors 1 and 2 is described. The embodiment of the present disclosure can also be applied to a motor control device with one axis or more than three axes. As in the above-mentioned form, even if the motor control device is a motor control device with more than three axes, the DC power source _S2 only needs to be set on one axis.

In the above-mentioned form, a three-phase AC power source _S1 is used as the first power source. Instead of a three-phase AC power source, a single-phase AC power source may be used as the first power source. In addition, in the above-mentioned form, a rectifier circuit is used as a DC supply unit. The DC supply unit may be a circuit capable of regenerating power such as a PWM converter. In this case, the measurement is performed while the PWM converter is stopped.

Furthermore, as the first power source, in addition to the AC power source, a DC power source such as a battery can be used. Furthermore, as the first switch, in addition to the electromagnetic contactor MS, a switch can be used. Furthermore, when the battery is installed and power is supplied from the battery to the motor control device, the contact or terminal itself electrically connected when the battery is installed can be regarded as the first switch.

Furthermore, in the above-mentioned form, a three-phase inverter including a semiconductor switching element is used as the motor control device _Cont1 , _Cont2 . In the case of driving a single-phase motor, a single-phase inverter may be used as the motor control device _Cont1 , _Cont2 . Moreover, the commutation method is not limited to the above-mentioned form, and may be a full-wave bridge or a half-wave bridge.

In the above-mentioned form, a normal insulating power supply (not shown) is used as a driving power supply for the semiconductor switching elements TR ₁ to TR _12. If necessary, a self-supporting power supply, a high withstand voltage IC, or a combination of other various power supplies can be selected.

Next, FIG. 2 shows a second aspect of the present disclosure.

The second switch _SW1 shown in FIG. 2 is not a switching switch, but is configured as a selection switch that contacts either one of a contact a connected only to the negative-side bus _ML- or a contact b connected to the second power supply unit _S2 .

The operation of the motor control devices _Cont1 and _Cont2 in this case is described below.

In normal motor control, in order to perform the same measurement as the first form of the present disclosure, the second switch SW ₁ is not yet connected to the contact b. At this time, the second switch SW ₁ can be in a neutral state or in a state connected to the contact a. In this state, the third switch SW ₂ remains disconnected, the electromagnetic contactor MS is turned on, and the motor control of each axis is performed through the inverter. At this time, the second switch SW ₁ remains in a state not yet connected to the contact b.

During insulation resistance testing, the motor control devices _Cont1 and _Cont2 operate as follows.

Stop the motor control operation of all axes, disconnect the semiconductor switching elements TR ₁ to TR ₁₂ , and cut off the electromagnetic contactor MS. Then, set the second switch SW ₁ to the state of selecting the contact a connected to the negative bus _ML- . Furthermore, the grounding circuit is formed by switching the third switch SW ₂ from the disconnected state to the conductive state. Then, after a predetermined time, the grounding circuit is cut off by switching the third switch SW ₂ from the conductive state to the disconnected state. In this state, measure the DC voltage V _PN of the inverter, the voltage _VR1A of the current detection resistor R ₁ , and the voltage _VR2A of the current detection resistor R ₂ .

Next, the second switch SW ₁ is set to a state where the contact b connected to the second power supply unit S ₂ is selected. Furthermore, the grounding circuit is formed by switching the third switch SW ₂ from disconnection to conduction. Next, the voltage V _DC of the DC power supply S ₂ is applied between the negative bus _ML- and the ground E. In this state, the voltage _VR1B of the current detection resistor R ₁ and the voltage _VR2B of the current detection resistor R ₂ are measured. From these current detection resistors R ₁ and R ₂ and the voltages _VR1B and _VR2B , the current (second current (value)) flowing in the current detection resistors R ₁ and R ₂ can be obtained.

The remaining operations and the method of measuring and calculating the insulation resistances R _m1 and R _m2 of the motors 1 and 2 are substantially the same as those of the first aspect of the present disclosure.

In the first and second forms of the present disclosure, the second and third switches have different structures. These switches are switches having the same technical meaning as the second and third switches, and any structure is irrelevant. In short, these switches are switches that can detect the current caused by the application of the voltage V _DC of the DC power source _S2 after the charge stored in the grounding capacitors _C3 and _C4 is discharged while measuring the insulation resistances _Rm1 and _Rm2 of the motors 1 and 2.

The above is a detailed description of the present disclosure. The technical scope of the present disclosure is not limited to those specifically indicated in the description so far, but is entirely included in the forms included in the matters described in the patent application. Moreover, each term or description is not intended to limit the technical scope of the present disclosure.

The above detailed description has been presented for the purpose of illustration and description. Many modifications and variations are possible in accordance with the above teachings. It is not intended to be exhaustive or to limit the subject matter of the invention described herein to the specific precise form disclosed. Although the subject matter of the invention has been described in terms of specific structural features and/or methodological acts, it should be understood that the subject matter of the invention as defined by the attached patent claims is not necessarily limited to the specific features or acts described above. On the contrary, the specific features and acts described above are disclosed as an example form of implementation of the attached patent claims.

1: Motor 2: Motor E: Ground R _m1 : Insulation resistance R _m2 : Insulation resistance C _ont1 : Motor control device 1 C _ont2 : Motor control device 2 S ₁ : Three-phase AC power supply (first power supply unit) MS: Electromagnetic contactor (first switch) S _DC : Rectifier circuit (DC supply unit) ML: Bus ML ₊ : Positive bus ML _- : Negative bus C ₁ : Smoothing capacitor (capacitor) C ₂ : Smoothing capacitor (capacitor) C ₃ : Grounding capacitor C ₄ : Grounding capacitor V _PN : DC voltage of inverter TR ₁ ~TR ₁₂ : Semiconductor switching element R _tr1 : Equivalent leakage resistance of semiconductor switching element R _tr2 : Equivalent leakage resistance of semiconductor switching element D _f : Flywheel diode 3 ₁ : Insulation resistance calculation unit 3 ₂ : Insulation resistance calculation unit S ₂ : DC power supply (second power supply unit) V _DC : Voltage of DC power supply SW ₁ : Switch (second switch) 4 ₁ : Detection control unit (current detection unit) 4 ₂ : Detection control unit (current detection unit) R ₁ : Current detection resistor R ₂ : Current detection resistor _VR1A : Voltage of current detection resistor R _{1 VR2A} : Voltage of current detection resistor R ₂ SW ₂ : Switch (third switch)

[Figure 1] is a circuit diagram showing the motor control device described in the first form of the present disclosure. [Figure 2] is a circuit diagram showing the motor control device described in the second form of the present disclosure.

1: Motor

2: Motor

3 ₁ : Insulation resistance calculation unit

3 ₂ : Insulation resistance calculation unit

4 ₁ : Detection control unit (current detection unit)

4 ₂ : Detection control unit (current detection unit)

C ₁ : Smoothing capacitor (capacitor)

C ₂ : Smoothing capacitor (capacitor)

C ₃ : Grounding capacitor

C ₄ : Grounding capacitor

C _ont1 : Motor control device 1

C _ont2 : Motor control device 2

D _f : Flywheel diode

E: Grounding

L: Winding

ML _- : Negative bus

ML ₊ : Positive busbar

MS: Electromagnetic contactor (1st switch)

R ₁ : Current detection resistor

R ₂ : Current detection resistor

R _m1 : Insulation resistance

R _m2 : Insulation resistance

R _tr1 : Equivalent leakage resistance of semiconductor switching device

R _tr2 : Equivalent leakage resistance of semiconductor switching device

_S1 : Three-phase AC power supply (1st power supply unit)

_S2 : DC power supply (second power supply unit)

S _DC : Rectifier circuit (DC supply section)

SW ₁ : Switch (2nd switch)

SW ₂ : Switch (3rd switch)

TR ₁ ~TR ₁₂ : Semiconductor switching devices

V _DC : DC power supply voltage

V _PN : DC voltage of inverter

_VR1A : Voltage across current sensing resistor _R1

_VR2A : Voltage across current sensing resistor _R2

Claims (9)

A motor control device comprises: a first power supply unit; a first switch, which can disconnect the power supply from the first power supply unit; a DC supply unit, which outputs the power from the first power supply unit to a bus; a capacitor, which is connected to the bus; a switching element, which converts the DC voltage supplied to the bus into an AC voltage, and drives and controls the motor with the AC voltage; a grounding capacitor, which is connected to the negative bus; a second switch, which can ground the negative bus; and a third switch, one end of which is connected to the second power supply unit connected to the bus. The first switch is connected to the first motor, and the other end can be grounded; a current detection unit detects the current value between the winding of the motor and the negative bus; and an insulation resistance calculation unit calculates the insulation resistance value of the motor based on the current value detected by the current detection unit, the voltage value of the capacitor, and the voltage value of the second power supply unit when the third switch is turned on and the third switch is turned off, respectively, when the power supply is cut off through the first switch, and the second switch is turned on for a specified time, so that the charge of the grounded capacitor is discharged. The motor control device of claim 1, wherein the second power supply unit is a DC power supply unit between the bus and the third switch; the insulation resistance calculation unit calculates the insulation resistance value of the motor based on the current value detected by the current detection unit when the third switch is turned on and off, the voltage value of the capacitor, and the voltage value of the second power supply unit. A motor control device as claimed in claim 2, wherein one end of the negative side of the DC power supply unit is connected to the negative side bus; and the voltage of the DC power supply unit is set to be lower than the voltage of the capacitor. The motor control device of claim 2 or 3, wherein the second switch and the third switch are connected in series in that order, starting from the negative bus; the second switch is a switch that can selectively connect at least the negative bus and the DC power supply to the third switch. A method for detecting insulation resistance of a motor control device, the motor control device comprising: a first power supply unit; a first switch capable of disconnecting power supply from the first power supply unit; a DC supply unit that outputs power from the first power supply unit to a bus; a capacitor connected to the bus; a switching element that converts the DC voltage supplied to the bus into an AC voltage and drives and controls the motor using the AC voltage; and a grounding capacitor connected to the negative bus. The method for detecting insulation resistance of the motor control device comprises: disconnecting power supply via the first switch; connecting the second switch capable of grounding the negative bus to a predetermined voltage; time to discharge the charge of the grounded capacitor; the process of setting the aforementioned third switch to open the second power source unit whose one end is connected to the aforementioned bus and the other end can be grounded through the third switch, and using the current detection unit to detect the first current value between the winding of the motor and the aforementioned bus connected to the aforementioned second power source unit; the process of setting the aforementioned third switch to close, and using the aforementioned current detection unit to detect the second current value between the winding of the motor and the aforementioned bus connected to the aforementioned second power source unit; and the process of calculating the insulation resistance value of the aforementioned motor based on the detected first current value and the aforementioned second current value, the voltage value of the capacitor and the voltage value of the aforementioned second power source unit. The insulation resistance detection method of the motor control device as claimed in claim 5, wherein the second power source is the charged capacitor connected to the bus; the voltage value of the second power source is the voltage value of the capacitor. The insulation resistance detection method of the motor control device of claim 5, wherein the second power supply unit is a DC power supply unit between the bus and the third switch; In the process of calculating the insulation resistance value of the motor, the insulation resistance value of the motor is calculated based on the current value detected by the current detection unit when the third switch is turned on and off, the voltage value of the capacitor, and the voltage value of the second power supply unit. As in claim 7, the insulation resistance detection method of the motor control device, wherein one end of the negative side of the DC power supply unit is connected to the negative side bus; the voltage of the DC power supply unit is set to be lower than the voltage of the capacitor. The insulation resistance detection method of the motor control device as claimed in claim 7 or 8, wherein the second switch and the third switch are connected in series in this order, starting from the negative bus; the second switch is a switch that can selectively connect at least the negative bus and the DC power supply unit to the third switch.

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