TWI853984B - Motor control apparatus and insulation resistance detection method for same - Google Patents

Abstract

Provided is a motor control apparatus which includes: a first power supply unit; a first switch which is able to cut off supply of power from the first power supply unit; a direct current supply unit configured to output power from the first power supply unit to a bus; a capacitor connected to the bus; and a switching element configured to convert direct current supplied to the bus to alternating current and control drive of a motor. The motor control apparatus includes: a second power supply unit connected at one end to the bus and grounded at the other end via a second switch; a current detection unit configured to detect a value of a current between a winding of the motor and the bus connected to the second power supply unit; and an insulation resistance calculation unit, configured to, after cutting off the supply of power by the first switch unit, calculate an insulation resistance value of the motor on the basis of current values detected by the current detection unit in open and closed states of the second switch, a voltage value of the capacitor, and a voltage value of the second power supply unit.

Description

Motor control device and insulation resistance detection method thereof

The present invention relates to a motor control device having a motor insulation resistance detection function, and an insulation resistance detection method of the motor control device.

Motors such as servomotors driven by motor control devices including inverters are widely used in machine tools. Cutting fluid is used when machining with these machine tools. Therefore, the cutting fluid attached to the motor enters the motor and causes the problem of deterioration of the motor insulation.

In addition, similar problems may occur when motors such as servomotors are used for a long period of time or due to the use environment other than machine tools.

The insulation of the motor gradually deteriorates, eventually causing a ground fault. The ground fault of the motor causes the leakage circuit breaker to trip, or the motor control device to be damaged, causing the system to 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.

As a document that discloses a method for detecting the insulation resistance of a motor, there is Japanese Patent Gazette No. 4961045. Japanese Patent Gazette No. 4961045 describes a motor drive device that is connected to a positive DC bus and a negative DC bus in a DC power source; it is characterized by having: a motor drive unit, which has an inverter part, and further, the inverter part converts DC power into AC power to drive the AC motor, and the inverter part has an arm switching element that switches the connection and disconnection of the AC motor; a low voltage source, which is provided between either the positive DC bus or the negative DC bus and the ground; a current detection part, It detects a closed-loop current flowing in a closed-loop circuit including a low-voltage source, an AC motor, and a part of an inverter unit when connected to any selected arm switching element, and a bias current flowing in the closed-loop circuit when all arm switching elements are disconnected; a bias removal unit calculates the difference between the closed-loop current value detected by the current detection unit and the bias current value; and an insulation resistance degradation determination unit determines the degradation of the insulation resistance of the AC motor by comparing the difference in the closed-loop current value with a specified threshold value.

Furthermore, Japanese Patent Gazette No. 2015-129704 discloses a motor drive device having: a rectifier circuit that rectifies an AC voltage supplied from an AC power source through a first switch into a DC voltage; a power supply unit that uses a capacitor to smooth the DC voltage rectified by the rectifier circuit; an inverter unit that converts the DC voltage smoothed by the power supply unit into an AC voltage to drive the motor through a switching action of a semiconductor switching element; and a current detection unit that detects the current flowing in a state having A current value of a resistor connected to one end of a coil of a motor and the other end connected to one terminal of a capacitor; a voltage detection unit that measures voltage values at both ends of the capacitor; a second switch that grounds the other terminal of the capacitor; and an insulation resistance detection unit that stops the operation of the motor, disconnects the first switch, and further uses two sets of current values and voltage values measured when the second switch is disconnected and when it is turned on, as resistance between the coil of the motor and the ground, to detect the insulation resistance value of the motor.

The motor control device related to the embodiment 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 a bus; a capacitor, which is connected to the bus; and a switching element, which converts the DC supplied to the bus into AC to drive the control motor; wherein the second power supply unit is further provided, one end of which is connected to the bus. The other end is grounded through a second switch; a current detection unit detects a current value between the winding of the motor and the bus bar connected to the second power supply unit; and an insulation resistance calculation unit disconnects the power supply via the first switch unit, and 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 each of the second switches is turned on and off.

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.

In the Japanese Patent Gazette No. 4961045, when the insulation resistance of multiple motors is detected, the bias current flowing in the closed loop containing the low voltage source, the AC motor, and a part of the inverter unit is detected when all the arm switching elements are disconnected. Then, when any one of the selected arm switching elements is in a connected state, the closed loop current flowing in the closed loop containing the low voltage source, the AC motor, and a part of the inverter unit is detected. Then, by finding the difference between the value of the closed loop current and the value of the bias current, the current based on the insulation resistance of the motor is calculated. If the insulation resistance of the motor does not decrease, the bias current will not flow. On the other hand, when the insulation resistance of the motor decreases, a voltage is applied to the semiconductor switching element from a low voltage source through the insulation resistance of the motor. Then, the leakage current of the semiconductor switching element flows. This current is a bias current. In the patent gazette of Japanese Patent No. 4961045, the bias current (leakage current of the semiconductor switching element) is measured. Then, the difference between the measurement result of the closed-loop current when the selected arm switching element is in a connected state and the bias current is obtained. In this way, the influence of the leakage current of the semiconductor switching element is removed. However, the measured bias current is equivalent to the entire axis of the measuring axis and the non-measuring axis. For this reason, the measured bias current also includes the bias current of the measuring axis. On the other hand, the current measured during closed-loop current measurement is obtained by adding the current based on the insulation resistance of the motor of the measuring axis and the bias current of the entire non-measuring axis. For this reason, the bias is removed by the difference between the closed-loop current and the bias current, and the following calculation result is obtained. Calculation result = Current based on the insulation resistance of the motor of the measuring axis + Bias current of the entire non-measuring axis - (Bias current of the measuring axis + Bias current of the entire non-measuring axis) = Current based on the insulation resistance of the motor of the measuring axis - Bias current of the measuring axis. As a result, unfortunately, an error occurs in the bias current of the measuring axis. Thus, in the method of Japanese Patent Gazette No. 4961045, when the insulation resistance of the motor decreases, it is impossible to accurately calculate the bias current of all axes other than the measuring axis. In other words, unfortunately, the calculation result also includes the bias current of the measuring axis. As a result, an error occurs in the bias current of the measuring axis. As a result, a problem occurs in that the current based on the insulation resistance of the correct motor cannot be measured.

Japanese Patent Publication No. 2015-129704 also calculates the insulation resistance of the motor from the results of the second measurement, similarly to Japanese Patent Publication No. 4961045. Then, in calculating the insulation resistance of the motor from the results of the second measurement, the equivalent resistance corresponding to the leakage current of each semiconductor switching element is eliminated. This eliminates the influence of the leakage current of the semiconductor switching element. There is no error in the leakage current of the measuring axis as in Japanese Patent Publication No. 4961045. Therefore, the measurement accuracy is higher than the method described in Japanese Patent Publication No. 4961045. However, in the method described in Japanese Patent Gazette No. 2015-129704, the voltage of the smoothing capacitor is applied to the insulation resistance of the motor. The smoothing capacitor suppresses the change of the DC voltage caused by the power supply frequency when driving the motor. For this purpose, an electrolytic capacitor with a relatively large capacitance is used. In addition, the internal impedance is also low. For this reason, for example, the insulation resistance of the motor is very small, and further, in the case where the negative side element of the semiconductor switching element is short-circuited and damaged, a very large current flows from the smoothing capacitor through the insulation deterioration part of the motor to the semiconductor switching element. As a result, there is a risk of secondary damage to the semiconductor switching element, or the insulation deterioration part of the motor is further deteriorated.

In addition, as the gate driving power source of the positive side semiconductor switching element of the inverter with a small capacitance, a self-lifting power source is used in some cases. As for the self-lifting power source, as shown in FIG. 4, the gate driving power source of the semiconductor switching elements TR1 to TR3 on the positive side is constituted via the gate driving power source _S3 for the semiconductor switching elements TR4 to TR6 on the negative side, the resistor Rb, the diode Db, and the capacitor Cb. By turning on and off the semiconductor switching elements TR4 to TR6 on the negative side, the capacitor Cb is charged from the gate driving power source _S3 for the semiconductor switching elements TR4 to TR6 on the negative side through the resistor Rb and the diode Db. In this way, the gate drive power of the semiconductor switching elements TR1 to TR3 on the positive side is formed. In this way, when the gate drive power of the semiconductor switching elements TR1 to TR3 on the positive side is formed by the self-lifting power supply, in the method described in Japanese Patent Publication No. 2015-129704, unfortunately, the current flows from the gate drive power of the semiconductor switching elements TR4 to TR6 on the negative side of the self-lifting power supply through the resistor Rb, the diode Db, and the capacitor Cb of the self-lifting power supply to the current detection resistor for insulation resistance detection. As a result, the problem of deterioration of insulation resistance detection accuracy occurs.

In addition, the gate control signals of the semiconductor switching elements TR1 to TR3 on the positive side are sometimes transmitted by using a high withstand voltage IC in addition to the self-powered power supply. When such a high withstand voltage IC is used to transmit the gate control signal, unfortunately, a current flows from the negative side gate driving power supply _S3 through the power supply of the high withstand voltage IC to the current detection resistor used for insulation resistance detection. As a result, the problem of deterioration of insulation resistance detection accuracy arises.

The present invention aims to solve the above-mentioned problem. Its purpose is to provide a motor control device which has no risk of secondary damage to semiconductor switching elements and no risk of further insulation degradation of the motor, and can be used as a motor control device including a self-supporting power supply or a high-voltage IC, and further, can accurately detect the insulation resistance of the motor.

A motor control device related to one aspect of the present invention for solving the aforementioned problem 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; and a switching element, which converts the DC supplied to the bus into AC to drive the control motor; and further comprises: a second power supply unit, one end of which is connected to the to the bus bar and grounding the other end thereof through a second switch; a current detecting unit detecting a current value between the winding of the motor and the bus bar connected to the second power supply unit; and an insulation resistance calculating unit calculating an insulation resistance value of the motor based on the current value detected by the current detecting unit, the voltage value of the capacitor, and the voltage value of the second power supply unit when power supply is cut off via the first switch unit and each of the second switches is turned on and off.

A motor control device related to another aspect of the present invention for solving the aforementioned problem comprises: a first power source, i.e., a DC power source that is not grounded; a DC supply unit, which outputs power from the first power source to a bus; a capacitor, which is connected to the bus; and a switching element, which converts the DC supplied to the bus into AC to drive the control motor; and a second power source, which converts one end of the DC power source to an AC source. connected to the bus bar and having the other end grounded through a second switch; a current detecting unit that detects a current value between the winding of the motor and the bus bar connected to the second power supply unit; and an insulation resistance calculating unit that calculates an insulation resistance value of the motor based on the current value detected by the current detecting unit, the voltage value of the capacitor, and the voltage value of the second power supply unit when the second switch is turned on and off.

A method for detecting insulation resistance of a motor control device related to another aspect of the present invention for solving the aforementioned problem, the motor control device comprises: a first power supply unit; a first switch, which can disconnect the power supply from the aforementioned first power supply unit; a DC supply unit, which outputs the power from the aforementioned first power supply unit to a bus; a capacitor, which is connected to the aforementioned bus; and a switching element, which converts the DC supplied to the aforementioned bus into AC to drive the control motor; wherein the method for detecting insulation resistance of the motor control device comprises: disconnecting the power supply via the aforementioned first switch; The second switch of the second power supply unit having one end connected to the bus and the other end grounded through the second switch is set to open; the first current value between the winding of the motor and the bus connected to the second power supply unit is detected by the current detection unit; the second switch is set to closed; the second current value between the winding of the motor and the bus connected to the second power supply unit is detected by the current detection unit; and the insulation resistance value of the motor is calculated based on the detected first current value and second current value, the voltage value of the capacitor and the voltage value of the second power supply unit.

A motor control device insulation resistance detection method related to another aspect of the present invention for solving the aforementioned problem comprises: a first power supply unit, that is, a DC power supply that has not been grounded; a DC supply unit, which outputs power from the first power supply unit to a bus; a capacitor, which is connected to the bus; and a switching element, which converts the DC supplied to the bus into AC to drive the control motor; wherein the motor control device insulation resistance detection method comprises: connecting one end of the capacitor to the bus and the other end of the capacitor to the bus; The invention relates to a process of setting the second switch of the second power supply unit connected to the ground of the switch to open; detecting the first current value between the winding of the motor and the bus connected to the second power supply unit by the current detection unit; setting the second switch to close; detecting the second current value between the winding of the motor and the bus connected to the second power supply unit by the current detection unit; and calculating the insulation resistance value of the motor based on the detected first current value and second current value, the voltage value of the capacitor, and the voltage value of the second power supply unit.

Other aspects of the present invention will become apparent from the description of embodiments for carrying out the invention described later.

According to the present invention, the power supply from the first power source unit is stopped by disconnecting the power supply using the first switch unit. In this state, when the second switch is set to the open state, the leakage current flowing through the switching element is used only by the voltage of the capacitor. Then, the first current value is detected by the current detection unit. On the other hand, in the state where the power supply from the first power source unit is stopped, when the second switch is set to the closed state, the second current value is detected by the current detection unit, which is the addition of the first current value and most of the current passing through the winding of the motor due to the voltage of the second power source unit alone (the remainder is a small leakage current of the switching element on the negative side). Based on the calculation of the two current values detected by the current detection unit, namely 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 accurately calculated.

Here, when the first power source is a DC power source that is not grounded, the first switch unit is not provided. Also, there is no process of disconnecting the power supply via the first switch unit. However, the other functions are the same.

Furthermore, according to the present invention, the voltage value of the second power supply unit is used to measure the current value passing through the winding of the motor. Therefore, as the voltage value of the capacitor used to detect the insulation resistance, it is not necessary to close the switching element by gate drive control of the switching element that drives the motor. Furthermore, the current capacity of the second power supply unit can be set to a small current capacity required for insulation resistance detection. Therefore, during measurement, there is no risk of secondary damage to the switching element or further deterioration of the insulation deterioration portion of the motor when a very large current flows from the capacitor through the insulation deterioration portion of the motor to the switching element on the negative side.

Furthermore, the insulation resistance detection method of the motor control device related to the present invention is applicable even when the switching element of the motor is driven by a self-powered power supply or a high-voltage IC, and the power supply can be stopped. Therefore, the insulation resistance value of the motor can be accurately calculated by performing the same calculation as above.

Moreover, here, the "first switch" includes all switches including a circuit breaker. Even if it is a terminal or a contact point that contacts with a battery or a terminal of a power source, it includes all switches that have a structure that can disconnect the power supply from the power source. Moreover, the "DC supply unit" is of course not only a power converter that converts AC to DC, but also includes a power converter that converts from DC to DC or maintains voltage. However, when a directly connected DC power source is used as the first power source, the connecting wires, contacts, and terminals constitute the "DC supply unit". In addition, when referred to as a "switch", the "switch" includes any switch other than the aforementioned "switch" as long as it can stop the current. Such switches also include mechanical switches, relays, and semiconductor switches.

As described above, according to the present invention, a motor control device can be provided, which does not have the risk of secondary damage to the switching element, nor does it have the risk of further insulation degradation of the motor. It can also be applied to a motor control device containing a self-powered power supply or a high-voltage IC, and further, the insulation resistance of the motor can be accurately detected. Implementation Example

FIG1 shows a first aspect of the present invention.

Furthermore, in the following description, current may include current value, voltage may include voltage value, impedance may include impedance value, and resistance may include resistance value. Moreover, these terms are interpreted according to the technical common sense of a person having ordinary knowledge in the relevant technical field. Furthermore, regarding the gate drive power supply of the semiconductor switching element, a common insulating power supply is used unless otherwise specified. For this reason, the detailed description of the gate drive power supply is omitted.

The motor control device Cont1 is configured by a rectifier circuit (DC supply unit) S _DC , a bus ML composed of a positive bus ML ₊ and a negative bus _ML- , a smoothing capacitor (capacitor) C1 , an inverter composed of semiconductor switching elements TR1 to TR6 , and an insulation resistance calculation unit 3 ₁ .

In the motor control device Cont1, the three-phase AC voltage supplied from the three-phase AC power source (first power source) _S1 through the electromagnetic contactor (first switch) MS that can cut off the power supply is full-wave rectified by the rectifier circuit (DC supply unit) S _DC . Then, the DC voltage is output to the bus ML.

The output DC voltage is smoothed via smoothing capacitors (capacitors) C1 and C2 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 bus ML ₊ and the bus _ML- is supplied to an inverter composed of semiconductor switching elements TR1 to TR6 connected between the positive bus ML ₊ and the negative bus _ML- . In this way, the motor 1 is driven by the AC obtained by inverting the DC supplied to the bus ML ₊ and the bus _ML- .

The motor control device Cont2 is configured using a bus ML composed of a positive bus ML ₊ and a negative bus _ML- , a smoothing capacitor (capacitor) C2, an inverter composed of semiconductor switching elements TR7 to TR12, and an insulation resistance calculation unit ₃₂ .

The motor control device Cont2 is supplied with a DC voltage from the rectifier circuit S _DC similarly to the motor control device Cont1. The DC voltage supplied to the bus ML is inverted into AC voltage by an inverter composed of semiconductor switching elements TR7 to TR12. In this way, the motor 2 is driven.

This state 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 is composed of a DC power supply (second power supply unit) _S2 provided between the negative bus ML- of the bus _ML and the ground E, a switch SW0 (first switch), a current detection resistor R1 connected to the negative bus _ML- and the winding L of the motor 1, and a detection control unit (current detection unit) ₄₁ which detects current from the voltage of the current detection resistor R1, 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 is composed of a current detection resistor R2 connected to 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 that detects current from the voltage of the current detection resistor R2 and 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 motor 1 or 2 of the shaft. The resistance of the winding L of the motor 1 and 2 is very small. Therefore, any phase can be detected.

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, and is used in a situation where the potential on the ground E side is higher than the negative bus _ML- . Furthermore, a power source with a small current capacity is used to the extent necessary for measurement.

The voltage of the DC power source _S2 is set lower than the voltage of the smoothing capacitors C1 and C2 in order to suppress the decrease in the detection accuracy of the insulating resistors Rm1 and Rm2 caused by the current. The current is the current that flows from the insulating resistors Rm1 and Rm2 of the motors 1 and 2 through the flywheel diodes Df of the semiconductor switching elements TR1~TR3, TR7~TR9 of the upper branch (positive side) of the inverter part to charge the smoothing capacitors C1 and C2 during measurement.

During normal motor control, switch SW0 remains OFF and electromagnetic contactor MS is ON. Then, the motor of each axis is controlled via the inverter. During insulation resistance detection, motor control devices Cont1 and Cont2 operate as follows.

The motor control operation of all axes is stopped, the semiconductor switching elements TR1 to TR12 are disconnected, and further, the electromagnetic contactor MS is cut off. Then, the DC voltage V _PN of the inverter, the voltage _VR1A of the current detection resistor R1, and the voltage _VR2A of the current detection resistor R2 are measured.

The voltage of the smoothing capacitors C1 and C2 is applied to the semiconductor switching elements TR1 to TR12 constituting the inverter, so that the DC voltage V _PN of the inverter is equal to the voltage of the smoothing capacitors C1 and C2 in essence. With such a voltage, a current flows from the semiconductor switching element TR1 to TR4. Furthermore, the current flows to the current detection resistor R1. Similarly, a current flows from the semiconductor switching element TR7 to TR10. Furthermore, the current flows to the current detection resistor R2.

The current flowing from the positive semiconductor switching element TR1 to TR4 and the current flowing from TR7 to TR10 are the leakage currents of the semiconductor switching elements. The leakage current flows in all phases in the same way. However, by focusing on one phase of the connected current detection resistors R1 and R2, the insulation resistance of the motor can be obtained.

The equivalent leakage resistance of each semiconductor switching element of TR1 and TR4 is determined as R _tr1 . Furthermore, the equivalent leakage resistance of each semiconductor switching element of TR7 and TR10 is determined as R _tr2 . The following equations (1) and (2) are established.

(V _PN -V _R1A )/R _tr1 =V _R1A /R _tr1 +V _R1A /R1…(1)

(V _PN -V _R2A )/R _tr2 =V _R2A /R _tr2 +V _R2A /R2…(2)

Next, the switch SW0 is turned on, and the voltage VDC of the DC power source _S2 is applied to the ground E with respect to the negative bus _ML- . Next, the voltage _VR1B of the current detection resistor R1 and the voltage _VR2B of the current detection resistor R2 are measured.

When the insulation of the motor 1 is degraded, the voltage of the DC power source _S2 is applied to the semiconductor switching element TR4 through the insulation resistor Rm1 of the motor. Then, the current flows to the current detection resistor R1 and the semiconductor switching element TR4.

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 insulation resistor Rm2 of the motor. Then, the current flows to the current detection resistor R2 and the semiconductor switching element TR10.

Then, the voltage of the smoothing capacitors C1 and C2, that is, the DC voltage V _PN of the inverter, is applied to the semiconductor switching elements TR1 and TR4. Therefore, a current flows from the semiconductor switching element TR1 to TR4. Furthermore, a current also flows to the current detection resistor R1.

Similarly, current flows from semiconductor switching element TR7 to TR10. Moreover, current also flows to current detection resistor R2.

The currents flowing from the semiconductor switching element TR1 to TR4 and the currents flowing from TR7 to TR10 are leakage currents of these semiconductor switching elements. However, the leakage currents of these semiconductor switching elements are generally smaller than the currents flowing due to the decrease in the insulation resistance of the motor. For this reason, it can be assumed that the voltages of the smoothing capacitors C1 and C2 hardly decrease.

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

(V _PN -V _R1B )/R _tr1 +(VDC-V _R1B )/Rm1=V _R1B /R _tr1 +V _R1B /R1…(3)

(V _PN -V _R2B )/R _tr2 +(VDC-V _R2B )/Rm2=V _R2B /R _tr2 +V _R2B /R2…(4)

The insulation resistance Rm1 of motor 1 can be obtained by solving the simultaneous equations of equations (1) and (3) as shown below.

Rm1=R1(VDC-V _R1B )(V _PN -2V _R1A )/{(V _R1B -V _R1A )V _PN }…(5)

Furthermore, the insulation resistance Rm2 of motor 2 can be obtained by solving the simultaneous equations of equations (2) and (4) as shown below.

Rm2=R2(VDC-V _R2B )(V _PN -2V _R2A )/{(V _R2B -V _R2A )V _PN }…(6)

These calculations are performed in 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 once. However, it does not matter if one or both of the voltages _VR1A and _VR2A measured multiple times are used.

When using various average values like this, not only can the influence of abnormal values caused by interference etc. be reduced, but also higher-precision insulation resistance values Rm1 and Rm2 can be obtained.

Next, the calculated insulation resistance values Rm1 and Rm2 are transmitted to the user device as information. The insulation resistance values Rm1 and Rm2 can be transmitted by any means. For example, it does not matter whether these resistance values are transmitted by wire or wirelessly.

Users who know the insulation resistance values Rm1 and Rm2 can judge that the insulation resistance has deteriorated when the relevant insulation resistance value is low. Then, based on the prediction of system shutdown caused by the motor due to ground fault, such inappropriate accidents can be suppressed by replacing the motor in advance.

In determining whether the insulation resistance has deteriorated, appropriate means of determination can be used. For example, the determination can be made by comparing with values learned experimentally or from experience, with initial values measured and recorded or memorized when the motor control device is initially set up using a normal product, or with other set values of safety standards.

The insulation resistances Rm1 and Rm2 of the motors 1 and 2 are very small. Furthermore, when the semiconductor switching elements TR4 to TR6 and TR10 to TR12 on the negative side of the semiconductor switching elements TR1 to TR12 are short-circuited and damaged, 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. However, 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, there is no risk of secondary damage to the negative-side semiconductor switching elements TR4 to TR6 and TR10 to TR12, or further, there is no risk of insulation degradation of the motors 1 and 2.

In the above embodiment, the present invention is described in a motor control device using two axes of two motors 1 and 2. However, the present invention can also be applied to a motor with one axis or more than three axes. As in the above embodiment, in the case of more than three axes, the DC power source _S2 can be provided on only one axis.

In the above-mentioned embodiment, a three-phase AC power source _S1 is used as the first power source. However, a single-phase AC power source may be used as the first power source instead of a three-phase AC power source. Furthermore, in the above-mentioned embodiment, a rectifier circuit is used as the DC supply unit. However, a circuit in which a power source such as a PWM converter can be regenerated may be used. In this case, measurement is performed after 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 may be used. Furthermore, an electromagnetic contactor may not be used. A switch may be used. Furthermore, if a battery is installed, when power is supplied from the battery to the motor control device, the contact or terminal itself electrically connected when the battery is installed may be regarded as the first switch.

When a DC power source such as a battery is used as the first power source, and when the DC power source itself is not grounded, the first switch is not necessary in principle. In this case, the voltage supplied to the DC power source, the voltage of the smoothing capacitor, and the DC voltage of the inverter formed by the semiconductor switching element are almost the same.

Furthermore, in the above-mentioned form, a three-phase inverter formed by a semiconductor switching element is used as the motor control device Cont1, Cont2. However, in the case of driving a single-phase motor, a single-phase inverter can also be used. Moreover, the commutation method is not limited to the method of the above-mentioned form. The method can be a full-wave bridge type or a half-wave bridge type.

Next, as a second aspect of the present invention, an aspect using a self-lifting power source will be described.

As shown in FIG. 2 , this mode is applied to the gate driving power supplies of the semiconductor switching elements TR1 to TR3 and TR7 to TR9 on the positive side of the inverter formed by the self-supporting power supply B.

In the self-supporting power source B used as the gate driving power source of the semiconductor switching elements TR1 to TR3 on the positive side of the motor control device Cont1, the gate driving power source (third power source unit) _S3 for the semiconductor switching elements TR4 to TR6 on the negative side, the resistor Rb, the diode Db, and the capacitor Cb are used to constitute the gate driving power source of the semiconductor switching elements TR1 to TR3 on the positive side.

By switching on and off the semiconductor switching elements TR4 to TR6 on the negative side, the gate driving power _S3 for the semiconductor switching elements on the negative side charges the capacitor Cb through the resistor Rb and the diode Db. Then, the gate driving power drives the gates of the semiconductor switching elements TR1 to TR3 on the positive side.

The motor control device Cont2 is also constructed in the same manner. The gate drive power supply _S3 for the semiconductor switching elements TR10 to TR12 on the negative side, the resistor Rb, the diode Db, and the capacitor Cb are used to construct the gate drive power supply for the semiconductor switching elements TR7 to TR9 on the positive side. The operation of the gate drive power supply is the same as that of the motor control device Cont1.

In this state, in the motor control device Cont1, a switch SW1 for cutting off the power supply is provided between the self-supporting power supply B used as the gate driving power supply of the semiconductor switching elements TR1 to TR3 on the positive side and the gate driving power supply _S3 for the semiconductor switching elements TR4 to TR6 on the negative side to which the power is supplied.

Similarly, in the motor control device Cont2, a switch SW2 for cutting off the power supply is provided between the self-supporting power supply B used as the gate driving power supply of the semiconductor switching elements TR7 to TR9 on the positive side and the gate driving power supply _S3 for the semiconductor switching elements TR10 to TR12 on the negative side to which the power is supplied.

In normal motor control, switch SW0 is turned off, SW1 and SW2 are kept on, and electromagnetic contactor MS is turned on. Then, motors 1 and 2 of each axis are driven through an inverter composed of semiconductor switching elements TR1 to TR12.

During insulation resistance detection, the motor control operation of all axes is stopped. Semiconductor switching elements TR1 to TR12 are disconnected. Then, electromagnetic contactor MS is disconnected. Switches SW1 and SW2 are disconnected. Then, the DC voltage V _PN of the inverter, which is equal to the voltage of the smoothing capacitor C, the voltage _VR1A of the current detection resistor R1, and the voltage _VR2A of the current detection resistor R2 are measured.

The voltage of the smoothing capacitor C is applied to the semiconductor switching elements TR1 to TR12 constituting the inverter. As a result, a current flows from the semiconductor switching element TR1 to TR4. Furthermore, the current flows to the current detection resistor R1. Similarly, a current flows from the semiconductor switching element TR7 to TR10. Furthermore, the current flows to 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.

Switches SW1 and SW2 are turned off. Therefore, current does not flow from gate drive power source _S3 for negative-side semiconductor switching elements TR4 to TR6 and TR10 to TR12 through resistor Rb, diode Db, and capacitor Cb of bootstrap power source B to current detection resistors R1 and R2 for insulation resistance detection.

Next, the switch SW0 is turned on, and the voltage VDC of the DC power source _S2 is applied to the ground E with respect to the negative bus _ML- . Next, the voltage _VR1B of the current detection resistor R1 and the voltage _VR2B of the current detection resistor R2 are measured.

When the insulation of the motor 1 is degraded, the voltage VDC of the DC power source _S2 is applied to the negative-side semiconductor switching element TR4 through the insulation resistor Rm1 of the motor, and a current flows through the current detection resistor R1 and the negative-side semiconductor switching element TR4.

Similarly, when the insulation of the motor 2 is degraded, the voltage VDC of the DC power source _S2 is applied to the negative-side semiconductor switching element TR10 through the insulation resistor Rm2 of the motor. Then, the current flows to the current detection resistor R2 and the negative-side semiconductor switching element TR10.

Then, the voltage V _PN of the smoothing capacitor C is applied to the semiconductor switching elements TR1 to TR12. As a result, a current flows from the semiconductor switching element TR1 to TR4, and a current also flows to the current detection resistor R1. Similarly, a current flows from the semiconductor switching element TR7 to TR10, and a current also flows to the current detection resistor R2.

The current flowing from the semiconductor switching element TR1 to TR4 and the current flowing from TR7 to TR10 are leakage currents of these semiconductor switching elements.

However, the leakage current from the semiconductor switching element TR1 to TR4 and the leakage current from TR7 to TR10 are smaller than the current flowing due to the decrease in the insulation resistance Rm1 and Rm2 of the motor. Therefore, the voltage of the smoothing capacitor C hardly decreases. From these measurement results, the insulation resistances Rm1 and Rm2 of the motors 1 and 2 can be obtained from the above-mentioned equations (5) and (6), as in the above-mentioned embodiment 1 of the present invention.

Here, the switches SW1 and SW2 are inserted in a position to simultaneously turn on and off the three phases. However, the switches SW1 and SW2 may be inserted in any phase to form a gate drive power supply.

In this embodiment, both motor control devices Cont1 and Cont2 are self-supporting power supplies B. However, even when motor control device Cont2 is self-supporting power supply B and the gate power supply of motor control device Cont1 is a normal insulating power supply, the insulating resistance can be detected in the same manner except that switch SW1 is not necessary.

Next, as a third aspect of the present invention, an aspect using a high withstand voltage IC driver power supply will be described.

As shown in FIG. 3 , in this mode, the present invention is applicable to the case where a high withstand voltage IC is used to transmit gate control signals of semiconductor switching elements TR1 to TR3 and TR7 to TR9 on the positive side of the inverter.

In normal motor control, switch SW0 is turned off, SW1 and SW2 are kept on, and electromagnetic contactor MS is turned on. Then, motors 1 and 2 of each axis are driven through an inverter composed of switching elements TR1 to TR12.

During insulation resistance detection, the motor control operation of all axes is stopped. Semiconductor switching elements TR1 to TR12 are disconnected. Then, electromagnetic contactor MS is disconnected. Switches SW1 and SW2 are disconnected. Then, the DC voltage V _PN of the inverter, which is equal to the voltage of the smoothing capacitor C, the voltage _VR1A of the current detection resistor R1, and the voltage _VR2A of the current detection resistor R2 are measured.

The voltage of the smoothing capacitor C is applied to the semiconductor switching elements TR1 to TR12 constituting the inverter. As a result, a current flows from the semiconductor switching element TR1 to TR4. Furthermore, a current flows to the current detection resistor R1.

Similarly, current flows from semiconductor switching element TR7 to TR10. Furthermore, current flows to current detection resistor R2. Current flowing from semiconductor switching element TR1 to TR4 and current flowing from TR7 to TR10 are leakage currents of these semiconductor switching elements.

The switches SW1 and SW2 are turned off. This prevents current from flowing from the gate driving power source _S3 for the negative-side semiconductor switching elements TR4 to TR6 and TR10 to TR12 through the power source of the high-withstand voltage IC to the current detection resistors R1 and R2 for insulation resistance detection.

Then, the switch SW0 is turned on. Then, the voltage VDC of the DC power source _S2 is applied to the ground E with respect to the negative bus _ML- . Then, the voltage _VR1B of the current detection resistor R1 and the voltage _VR2B of the current detection resistor R2 are measured.

From these measurement results, the insulation resistances Rm1 and Rm2 of the motor 1 and the motor 2 can be obtained through the above-mentioned equations (5) and (6), similarly to the first and second aspects of the present invention.

Here, the switches SW1 and SW2 are inserted in a position to simultaneously turn on and off the three phases. However, the switches SW1 and SW2 may be inserted in any phase to form a gate drive power supply to a high withstand voltage IC.

It is also possible to use a combination of a self-supporting power supply and a high withstand voltage IC. In this case, as in the above-mentioned forms 2 and 3, the switches SW1 and SW2 provided cut off the connection path from the gate drive power supply to both the self-supporting power supply and the high withstand voltage IC. In this way, the insulation resistances Rm1 and Rm2 of the motors 1 and 2 can be detected.

Of course, as a gate drive power supply, a switching element used in a conventional insulating power supply can also be used in combination.

The above is a detailed description of the present invention. However, the technical scope of the present invention is not limited to the specific embodiments described so far. The aspects included in the matters described in the scope of the patent application include all the embodiments of the present invention. Moreover, each term and description should not be interpreted as limiting the scope of the technology.

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 examples of embodiments for implementing the attached patent claims.

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) B: Self-supporting power supply C: Smoothing capacitor C1: Smoothing capacitor (capacitor) C2: Smoothing capacitor (capacitor) Cb: Capacitor Cont1: Motor control device Cont2: Motor control device Db: Diode Df: Flywheel diode E: Ground L: Winding ML _- : Negative bus ML ₊ : Positive bus MS: Electromagnetic contactor (first switch) R1: Current detection resistor R2: Current detection resistor Rb: Resistor Rm1: Insulation resistor Rm2: Insulation resistor R _tr1 : equivalent leakage resistance R of semiconductor switching element _tr2 : equivalent leakage resistance _S1 : three-phase AC power supply (first power supply unit) _S2 : DC power supply (second power supply unit) _S3 : gate drive power supply _SDC : rectifier circuit (DC supply unit) SW0: switch (first switch) SW1: switch SW2: switch TR1: semiconductor switching element TR10: semiconductor switching element TR11: semiconductor switching element TR12: semiconductor switching element TR2: semiconductor switching element TR3: semiconductor switching element TR4: semiconductor switching element TR5: semiconductor switching element TR6: semiconductor switching element TR7: semiconductor switching element TR8: semiconductor switching element TR9: semiconductor switching element VDC: DC power supply S ₂ voltage V _PN : DC voltage of the inverter (voltage of smoothing capacitors C, C1, C2) _VR1A : Voltage of current detection resistor R1 _VR2A : Voltage of current detection resistor R2

[FIG. 1] is a circuit diagram showing a motor control device related to the first aspect of the present invention. [FIG. 2] is a circuit diagram showing a motor control device related to the second aspect of the present invention including a self-powered power supply. [FIG. 3] is a circuit diagram showing a motor control device related to the third aspect of the present invention including a high withstand voltage IC for driving a switching element. [FIG. 4] is a circuit diagram showing one example of a known motor control device.

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)

C1: Smoothing capacitor (capacitor)

C2: Smoothing capacitor (capacitor)

Cont1: Motor control device

Cont2: Motor control device

E: Grounding

L: Winding

ML _- : Negative busbar

ML ₊ : Busbar on the positive side

MS: Electromagnetic contactor (1st switch)

R1: Current detection resistor

R2: Current detection resistor

Rm1: Insulation resistance

Rm2: 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)

SW0: switch (1st switch)

TR1: Semiconductor switching element

TR2: Semiconductor switching element

TR3: Semiconductor switching element

TR4: Semiconductor switching element

TR5: Semiconductor switching element

TR6: Semiconductor switching element

TR7: Semiconductor switching element

TR8: Semiconductor switching element

TR9: Semiconductor switching element

TR10: Semiconductor switching element

TR11: Semiconductor switching device

TR12: Semiconductor switching device

V _DC : Voltage of DC power source S ₂

V _PN : DC voltage of the inverter (voltage of smoothing capacitors C, C1, C2)

V _R1A : Voltage across current sensing resistor R1

Claims (9)

A motor control device comprises: a first power supply unit; a first switch capable of disconnecting 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 connected to the bus; and a switching element that converts the DC supplied to the bus into AC to drive a control motor; and a second power supply unit having one end connected to the bus and the other end connected to the bus. The switch is grounded; a current detection unit detects the current value between the winding of the motor and the bus connected to the second power supply unit; and an insulation resistance calculation unit disconnects the power supply via the first switch, and calculates the insulation resistance value of the motor based on the current value detected by the current detection unit, the voltage value maintained by the capacitor, and the voltage value generated by the second power supply unit when each of the second switches is turned on and off. A motor control device comprises: a first power source, i.e., a DC power source that is not grounded; a DC supply unit, which outputs power from the first power source to a bus; a capacitor, which is connected to the bus; and a switching element, which converts the DC supplied to the bus into AC to drive the control motor; and a second power source, one end of which is connected to the bus and the other end is connected to the bus. The second switch is grounded; a current detection unit detects the current value between the winding of the motor and the bus connected to the second power supply unit; 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 maintained by the capacitor, and the voltage value generated by the second power supply unit when each of the second switches is turned on and off. A motor control device as claimed in claim 1 or 2, wherein the switching element of at least one of the motors includes a self-powered power supply; the motor control device further comprises: a third switch, which disconnects the power supply to the self-powered power supply when the third switch is turned on; and the current detection unit detects the current value when the third switch is turned on. The motor control device of claim 1 or 2, wherein the switching element of at least one of the motors comprises a high withstand voltage IC for gate driving that transmits a gate control signal; the motor control device further comprises: a third switch, which, when turned on, cuts off the power supply to the high withstand voltage IC; and the current detection unit, when the third switch is turned on, calculates the current value of the at least one of the motors. A motor control device as claimed in claim 1 or 2, wherein the second power supply unit is connected to the bus at one end on the negative side or the positive side thereof, and the other end is grounded; and the voltage value generated by the second power supply unit is set to be smaller than the voltage value maintained by the capacitor. A method for detecting insulation resistance of a motor control device, the motor control device comprising: 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; and a switching element, which converts the DC supplied to the bus into AC to drive a control motor; wherein the method for detecting insulation resistance of the motor control device comprises: disconnecting the power supply through the first switch; connecting one end of the capacitor to the bus and the other end of the capacitor to the second switch; The process of setting the aforementioned second switch of the grounded second power supply unit to open; the process of detecting the first current value between the winding of the aforementioned motor and the aforementioned bus connected to the aforementioned second power supply unit by using the current detection unit; the process of setting the aforementioned second switch to close; the process of detecting the second current value between the winding of the aforementioned motor and the aforementioned bus connected to the aforementioned second power supply unit by using the aforementioned current detection 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 maintained by the aforementioned capacitor, and the voltage value generated by the aforementioned second power supply unit. A method for detecting insulation resistance of a motor control device, the motor control device comprising: a first power supply unit, that is, a DC power supply that is not grounded; a DC supply unit that outputs power from the first power supply unit to a bus; a capacitor that is connected to the bus; and a switching element that converts the DC supplied to the bus into AC to drive a control motor; wherein the method for detecting insulation resistance of the motor control device comprises: connecting the second power supply unit, one end of which is connected to the bus and the other end of which is grounded through the second switch, to the second switch; The process of opening the motor; the process of detecting the first current value between the winding of the motor and the bus connected to the second power supply unit by using the current detection unit; the process of setting the second switch to close; the process of detecting the second current value between the winding of the motor and the bus connected to the second power supply unit by using the current detection unit; and the process of calculating the insulation resistance value of the motor based on the detected first current value and the second current value, the voltage value maintained by the capacitor and the voltage value generated by the second power supply unit. The method for detecting insulation resistance of a motor control device as claimed in claim 6 or 7, wherein the motor control device is further provided with: the switching element is further provided with at least one self-supporting power source; and a third switch, which, when turned on, disconnects the power supply to the self-supporting power source; the process of detecting the first current value and the process of detecting the second current value are performed when the third switch is turned on. An insulation resistance detection method for a motor control device as claimed in claim 6 or 7, wherein the motor control device is further provided with: the switching element, which is further provided with at least one high-voltage IC for transmitting a gate control signal and driving a gate; and a third switch, which disconnects the power supply to the high-voltage IC when turned on; the process of detecting the first current value and the process of detecting the second current value are performed when the third switch is turned on.

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