Motor control device and insulation resistance detection method thereof

Abstract

A motor control device includes a first power supply section, a first switch capable of disconnecting power supply from the first power supply section, a DC supply section that outputs power from the first power supply section to a bus, a capacitor connected to the bus, a switching element that converts DC supplied to the bus into AC to drive and control a motor, a second power supply section having one end connected to the bus and the other end grounded via a second switch, a current detection section that detects a current value between a coil of the motor and the bus connected to the second power supply section, and an insulation resistance calculation section that calculates an insulation resistance value of the motor based on current values detected by the current detection section at the time of disconnection and at the time of connection of the second switch, a voltage value of the capacitor, and a voltage value of the second power supply section when the power supply is disconnected by the first switch section.

Description

Technical Field

[0001] This invention relates to a motor control device with insulation resistance detection function for motors and a method for detecting the insulation resistance of the motor control device. Background Technology

[0002] Servo motors and other motors driven by motor control devices including inverters are used in machine tools and the like. These machine tools use cutting fluid during machining operations. Therefore, depending on the type of cutting fluid, the fluid adhering to the motor can enter the motor's interior, causing insulation degradation.

[0003] Furthermore, even when used in applications other than machine tools, servo motors and other motors can experience the same problems when used for extended periods or depending on the environment.

[0004] The insulation of a motor gradually deteriorates, eventually leading to grounding. Grounding of the motor can cause the residual current circuit breaker to trip or damage the motor control unit, resulting in system failure. System failure can have a significant impact on the factory's production line. Therefore, for preventative maintenance, a device capable of detecting the insulation resistance of the motor is needed.

[0005] Japanese Patent Publication No. 4961045 discloses a method for detecting the insulation resistance of such an electric motor. Japanese Patent Publication No. 4961045 discloses a motor drive device comprising: a motor drive unit connected to a positive DC bus and a negative DC bus in a DC power supply and having an inverter section, the inverter section having an arm switch element for switching the connection and disconnection with an AC motor, and the motor drive unit converting DC power to AC power through the inverter section to drive the AC motor; a low voltage source provided between either the positive or negative DC bus and ground; a current detection unit that, when connected to any selected arm switch element, detects a closed-circuit current flowing through a closed circuit including the low voltage source, the AC motor, and a portion of the inverter section, and detects an offset current flowing through the closed circuit when all arm switch elements are disconnected; an offset removal unit that calculates the difference between the value of the closed-circuit current detected by the current detection unit and the value of the offset current; and an insulation resistance degradation determination unit that determines the degradation of the insulation resistance of the AC motor by comparing the difference based on the value of the closed-circuit current with a predetermined threshold.

[0006] Furthermore, the motor drive device described in Japanese Patent Publication No. 2015-129704 includes: a rectifier circuit that rectifies an AC voltage supplied from an AC power source into a DC voltage using a first switch; a power supply unit that smooths the DC voltage rectified by the rectifier circuit using a capacitor; an inverter unit that converts the DC voltage smoothed by the power supply unit into an AC voltage and drives the motor by switching a semiconductor switching element; a current detection unit that measures the current flowing through a resistor, one end of which is connected to the motor winding and the other end to a terminal of a capacitor; a voltage detection unit that measures the voltage across the capacitor; a second switch that grounds the other terminal of the capacitor; and an insulation resistance detection unit that measures the insulation resistance of the motor, which is the resistance between the motor winding and the ground, by using two sets of current and voltage values ​​measured when the motor stops, the first switch is open, and the second switch is open and closed, respectively.

[0007] According to Japanese Patent Publication No. 4961045, when detecting the insulation resistance of multiple motors, with all arm switch elements disconnected, the offset current flowing through a closed circuit including a low-voltage source, an AC motor, and a portion of an inverter section is detected. Then, with any selected arm switch element connected, the closed-circuit current flowing through the closed circuit including the low-voltage source, an AC motor, and a portion of an inverter section is detected. Furthermore, the current based on the motor's insulation resistance is calculated by determining the difference between the closed-circuit current and the offset current. If the motor's insulation resistance does not decrease, no offset current is generated. On the other hand, when the motor's insulation resistance decreases, a voltage is applied to the semiconductor switch element from the low-voltage source through the motor's insulation resistance. This generates a leakage current in the semiconductor switch element. This current is called the offset current. According to Japanese Patent Publication No. 4961045, this offset current (the leakage current of the semiconductor switch element) is measured. Furthermore, the difference between the measured closed-circuit current when the selected arm switch element is connected and the offset current is obtained. In this way, the influence of the semiconductor switch element's leakage current is eliminated. However, the measured offset current corresponds to the entire shaft portion, both the measuring shaft and the non-measuring shaft portions. Therefore, the measured offset current also includes the offset current of the measuring shaft. On the other hand, the current measured during closed-circuit current measurement is obtained by adding the current based on the insulation resistance of the motor along the measuring shaft to the offset current of the entire shaft, both the non-measuring shaft and the non-measuring shaft portions. Therefore, by removing the offset from the difference between the closed-circuit current and the offset current, the following calculation result is obtained.

[0008] Calculation result = Current based on the insulation resistance of the motor on the measuring axis + Offset current of the entire non-measuring axis - (Offset current of the measuring axis + Offset current of the entire non-measuring axis)

[0009] = Current based on the insulation resistance of the motor measuring the shaft - Offset current of the measuring shaft

[0010] Therefore, an error occurs in the measurement of the offset current portion of the shaft. Thus, according to the method in Japanese Patent Publication No. 4961045, when the insulation resistance of the motor decreases, the offset current of the entire shaft (excluding the measurement shaft) cannot be accurately calculated. That is, the calculation result also includes the offset current of the measurement shaft. Therefore, an error occurs in the measurement of the offset current portion of the shaft. As a result, the current based on the motor's insulation resistance cannot be accurately measured.

[0011] Japanese Patent Publication No. 2015-129704, like Japanese Patent Publication No. 4961045, calculates the insulation resistance of the motor based on two measurements. Furthermore, in the process of calculating the motor's insulation resistance based on the two measurements, the equivalent resistance corresponding to the leakage current of each semiconductor switching element is eliminated. Thus, the influence of the leakage current of the semiconductor switching elements is eliminated. There is no error in measuring the leakage current portion of the measuring shaft as in Japanese Patent Publication No. 4961045. Therefore, the measurement accuracy is higher than that described in Japanese Patent Publication No. 4961045. However, according to the method described in Japanese Patent Publication No. 2015-129704, a voltage from a smoothing capacitor is applied to the insulation resistance of the motor. The smoothing capacitor suppresses DC voltage fluctuations caused by the power supply frequency when driving the motor. Therefore, a relatively large-capacity electrolytic capacitor is used. In addition, the internal impedance is low. Therefore, for example, when the insulation resistance of the motor is very low and 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 deteriorated insulation of the motor to the semiconductor switching element. As a result, there is a risk of secondary damage to the semiconductor switching element or further deterioration of the deteriorated insulation of the motor.

[0012] In addition, bootstrap power supplies are sometimes used as the gate drive power for the positive-side semiconductor switching elements of small-capacity inverters. Bootstrap power supplies, such as... Figure 4As shown, the gate drive power supply for the positive semiconductor switching elements TR1 to TR3 is formed by the gate drive power supply S3, resistor Rb, diode Db, and capacitor Cb provided for the negative semiconductor switching elements TR4 to TR6. By switching the negative semiconductor switching elements TR4 to TR6 on and off, the gate drive power supply S3 for the negative semiconductor switching elements TR4 to TR6 is charged through resistor Rb, diode Db, and capacitor Cb. This forms the gate drive power supply for the positive semiconductor switching elements TR1 to TR3. When the gate drive power supply for the positive semiconductor switching elements TR1 to TR3 is composed of a bootstrap power supply, according to the method described in Japanese Patent Publication No. 2015-129704, current flows from the gate drive power supply of the negative semiconductor switching elements TR4 to TR6 of the bootstrap power supply through resistor Rb, diode Db, and capacitor Cb to the current sensing resistor for insulation resistance detection. Therefore, a problem of deteriorated insulation resistance detection accuracy occurs.

[0013] Furthermore, sometimes the gate control signals of the positive-side semiconductor switching elements TR1 to TR3 are transmitted via a high-voltage IC instead of a bootstrap power supply. When this high-voltage IC is used to transmit the gate control signals, current also flows from the negative-side gate drive power supply S3 through the power supply of the high-voltage IC to the current sensing resistor used for insulation resistance detection. Therefore, a problem of deterioration in the accuracy of insulation resistance detection occurs. Summary of the Invention

[0014] This invention aims to eliminate the aforementioned problems. The purpose of this invention is to provide a motor control device that prevents secondary damage to semiconductor switching elements, avoids further insulation degradation of the motor, can be used as a motor control device incorporating a bootstrap power supply or a high-voltage IC, and can accurately detect the insulation resistance of the motor.

[0015] To solve the above-mentioned problems, one aspect of the present invention provides a motor control device, comprising: a first power supply unit; a first switch capable of disconnecting the power supply from the first power supply unit; a DC supply unit for outputting power from the first power supply unit to a bus; a capacitor connected to the bus; a switching element for converting the DC power supplied to the bus into AC power to drive and control the motor; a second power supply unit, one end of which is connected to the bus and the other end of which is grounded via a second switch; a current detection unit for detecting the current value between the motor coil and the bus connected to the second power supply unit; and an insulation resistance calculation unit for calculating the insulation resistance value of the motor based on the current value detected by the current detection unit when the power supply is disconnected by the first switch, the voltage value of the capacitor, and the voltage value of the second power supply unit when the second switch is open and closed, respectively.

[0016] To solve the above-mentioned problems, another aspect of the present invention provides a motor control device, comprising: a first power supply unit, which is an ungrounded DC power supply; a DC supply unit, which outputs power from the first power supply unit to a bus; a capacitor connected to the bus; a switching element, which converts the DC power supplied to the bus into AC power to drive and control the motor; a second power supply unit, one end of which is connected to the bus and the other end of which is grounded via a second switch; a current detection unit, which detects the current value between the coil of the motor and the bus connected to the second power supply unit; and an insulation resistance calculation unit, which 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 second switch is open and closed, respectively.

[0017] To address the aforementioned problems, another aspect of the present invention provides an insulation resistance detection method for a motor control device. The motor control device includes: a first power supply unit; a first switch capable of disconnecting the power supply from the first power supply unit; a DC supply unit outputting power from the first power supply unit to a bus; a capacitor connected to the bus; and a switching element converting the DC power supplied to the bus into AC power to drive and control the motor. The insulation resistance detection method of the motor control device includes: disconnecting the power supply by the first switch; opening the second switch of the second power supply unit, one end of which is connected to the bus and the other end grounded via the second switch; detecting a first current value between the motor coil and the bus connected to the second power supply unit by a current detection unit; closing the second switch; detecting a second current value between the motor coil 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 and second current values, the voltage value of the capacitor, and the voltage value of the second power supply unit.

[0018] To address the aforementioned problems, another aspect of the present invention provides an insulation resistance detection method for a motor control device. The motor control device includes: a first power supply unit, which is an ungrounded DC power supply; a DC supply unit, which outputs power from the first power supply unit to a bus; a capacitor connected to the bus; and a switching element, which converts the DC power supplied to the bus into AC power to drive and control the motor. The insulation resistance detection method of the motor control device includes: opening a second switch of a second power supply unit, one end of which is connected to the bus and the other end grounded via a second switch; detecting a first current value between the motor coil and the bus connected to the second power supply unit by a current detection unit; closing the second switch; detecting a second current value between the motor coil 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 and second current values, the voltage value of the capacitor, and the voltage value of the second power supply unit.

[0019] Other aspects of the invention are illustrated by embodiments of the methods used to implement the invention described later.

[0020] According to the present invention, the power supply from the first power source is stopped by disconnecting the power supply from the first switch. When the second switch is opened in this state, leakage current is generated solely through the voltage of the capacitor via the switching element. Furthermore, a first current value is detected by the current detection unit. Conversely, also in the state where the power supply from the first power source is stopped, when the second switch is closed, the current detection unit detects the first current value and a second current value, which is a superimposed sum of most of the current flowing through the motor coil generated solely by the voltage of the second power source (the remainder being a small leakage current from the negative-side switching element). By calculating based on the two current values ​​detected by the current detection unit—the first and second current values—the voltage values ​​of the capacitor and the second power source—the insulation resistance value of the motor can be calculated with high accuracy.

[0021] Here, when the first power supply is an ungrounded DC power supply, a first switch is not provided. Furthermore, there is no process for the first switch to disconnect the power supply. However, the rest of the functions are the same.

[0022] Furthermore, according to the present invention, the current value passing through the motor coil is measured using the voltage value of the second power supply unit. Therefore, even if the voltage value of the capacitor is used for insulation resistance detection, it is not necessary to close the switching element by driving the gate 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 necessary for insulation resistance detection. Therefore, there is no risk of a very large current flowing from the capacitor through the deteriorated insulation of the motor into the negative-side switching element during measurement, thus eliminating the risk of secondary damage to the switching element and further deterioration of the deteriorated insulation of the motor.

[0023] Furthermore, according to the insulation resistance detection method of the motor control device of the present invention, even if the switching element that drives the motor is driven by a bootstrap power supply or a high-voltage IC, the method can be applied simply by stopping the power supply. Therefore, by performing the same calculations as described above, the insulation resistance value of the motor can be calculated with high accuracy.

[0024] Furthermore, here, "first switch" includes all switches that include a circuit breaker. This includes all switches that have a structure capable of disconnecting the power supply, even those terminals or contacts that are in contact with the battery or power source. In addition, "DC supply unit" naturally includes not only power converters that convert AC to DC, but also power converters that convert or maintain voltage from DC to DC. 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." Furthermore, the term "switch" includes any switch that can block current, in addition to the aforementioned "switch." Such switches also include mechanical switches, relays, and semiconductor switches.

[0025] As described above, the motor control device according to the present invention can provide a motor control device that does not cause secondary damage to the switching element, does not cause further insulation degradation of the motor, and can be applied to motor control devices that include bootstrap power supplies or high-voltage ICs. Furthermore, it provides a motor control device that can detect the insulation resistance of the motor with high precision. Attached Figure Description

[0026] Figure 1 This is a circuit diagram illustrating the motor control device according to the first aspect of the present invention.

[0027] Figure 2 This is a circuit diagram illustrating a motor control device according to a second aspect of the present invention, which includes a bootstrap power supply.

[0028] Figure 3 This is a circuit diagram of a third-party motor control device of the present invention, which includes a high-voltage IC for driving switching elements.

[0029] Figure 4 This is a circuit diagram representing an example of an existing motor control device. Detailed Implementation

[0030] In the following detailed description, numerous specific details are presented for illustrative purposes and to provide a thorough understanding of the disclosed embodiments. However, it will be apparent that one or more embodiments can be implemented without these specific details. In other instances, well-known structures and apparatuses are shown schematically for the purpose of simplifying the drawings.

[0031] Example

[0032] Figure 1 This represents the first aspect of the present invention.

[0033] Furthermore, in the following description, current may include a current value, voltage may include a voltage value, impedance may include an impedance value, and resistance may include a resistance value. Additionally, the above terms are interpreted according to common sense among those skilled in the art. Furthermore, unless otherwise specified, the gate drive power supply for the switching element of the semiconductor uses a conventional isolated power supply. Therefore, a detailed description of the gate drive power supply is omitted.

[0034] The motor control unit Cont1 includes: a rectifier circuit (DC supply unit) S DC ; by the positive side busbar ML + and the negative side busbar ML - The busbar ML; the smoothing capacitor (capacitor) C1; the inverter composed of semiconductor switching elements TR1 to TR6; and the insulation resistance calculation unit 31.

[0035] In the motor control device Cont1, the three-phase AC voltage supplied from the three-phase AC power supply (first power supply unit) S1 by means of the electromagnetic contactor (first switch) MS, which can disconnect the power supply, is rectified by the rectifier circuit (DC supply unit) S. DC Full-wave rectification. Then, DC voltage is output to the bus ML.

[0036] The output DC voltage is supplied through bus ML connected to the positive side of bus ML. + and the negative side busbar ML - Smoothing between capacitors C1 and C2.

[0037] Supply to bus ML + and busbar ML - The smoothed DC voltage is supplied to the bus ML connected to the positive side. + and the negative side busbar ML - An inverter consisting of semiconductor switching elements TR1 to TR6 is used between them. Thus, by utilizing the power supplied to the bus ML... + ML - The AC obtained by inverting DC is used to drive motor 1.

[0038] Motor control unit Cont2 includes: a bus ML on the positive side + and the negative side busbar ML - The busbar ML; the smoothing capacitor (capacitor) C2; the inverter composed of semiconductor switching elements TR7 to TR12; and the insulation resistance calculation unit 32.

[0039] Motor control unit Cont2 and motor control unit Cont1 are together supplied from rectifier circuit S DC The DC voltage supplied to the bus ML is converted to AC using an inverter composed of semiconductor switching elements TR7 to TR12. This drives the motor 2.

[0040] The above method describes a structure for a two-axis drive where motor 1 and motor 2 drive separate axes.

[0041] The insulation resistance calculation unit 31 of the motor control device Cont1 includes: a negative busbar ML installed in the busbar ML. - DC power supply (second power supply unit) S2 between ground E; switch SW0 (first switch); connected to the negative busbar ML - The current detection resistor R1 of the coil L of motor 1; and the detection control unit (current detection unit) 41, which detects the current based on the voltage of the current detection resistor R1, controls the detection action of the insulation resistance, and calculates the insulation resistance value.

[0042] The insulation resistance calculation unit 32 of the motor control device Cont2 includes: the negative busbar ML connected to the busbar ML. - The current detection resistor R2 of the coil L of motor 2; and the detection control unit (current detection unit) 42, which detects the current based on the voltage of the current detection resistor R2, and calculates the insulation resistance value.

[0043] The current sensing resistors R1 and R2 are connected only to the coil L of one phase of each of the U, V, and W phases of motor 1 or 2 on its shaft. The resistance of the coil L of motor 1 and 2 is very small. Therefore, current sensing can be performed on any phase.

[0044] DC power supply S2 is a power source with the highest possible voltage within a voltage range lower than that of smoothing capacitors C1 and C2, used to make the potential of the ground E side higher than that of the negative bus ML. - Furthermore, a power supply with a very small current capacity is used to measure the extent necessary.

[0045] Setting the voltage of DC power supply S2 to be lower than the voltage of smoothing capacitors C1 and C2 is to suppress the freewheeling diodes D of semiconductor switching elements TR1-TR3 and TR7-TR9 on the upper arm (positive side) of the inverter section from flowing through the insulation resistances Rm1 and Rm2 of motors 1 and 2 during measurement. f The current flowing in the direction of charging the smooth capacitors C1 and C2 causes a decrease in the detection accuracy of insulation resistances Rm1 and Rm2.

[0046] During normal motor control, with switch SW0 open, electromagnetic contactor MS is activated. Then, the inverter controls the motors on each axis. During insulation resistance detection, motor control devices Cont1 and Cont2 operate as follows.

[0047] The entire shaft motor control operation stops, semiconductor switching elements TR1 to TR12 are disconnected, and electromagnetic contactor MS is disconnected. Then, the DC voltage V of the inverter is measured. PN The voltage V across the current sensing resistor R1 R1A and the voltage V across the current sensing resistor R2 R2A .

[0048] The voltage across smoothing capacitors C1 and C2 is applied to the semiconductor switching elements TR1 to TR12 that constitute the inverter, therefore the DC voltage V of the inverter... PN The voltage across the smoothing capacitors C1 and C2 is essentially equal. Due to this voltage, current flows from semiconductor switching element TR1 to TR4. Additionally, current flows to current sensing resistor R1. Similarly, current flows from semiconductor switching element TR7 to TR10. Furthermore, current flows to current sensing resistor R2.

[0049] The current flowing from the positive-side semiconductor switching element TR1 to TR4 and from TR7 to TR10 are the leakage currents of the semiconductor switching elements. Leakage current also flows through all phases. However, by focusing on the phase connected to current sensing resistors R1 and R2, the insulation resistance of the motor can be determined.

[0050] Let R be the equivalent leakage resistance of each semiconductor switching element of TR1 and TR4. tr1 Furthermore, the equivalent leakage resistance of the semiconductor switching elements of TR7 and TR10 is R. tr2 The following formulas (1) and (2) hold true.

[0051] (V PN -V R1A ) / R tr1 =V R1A / R tr1 +V R1A / R1···(1)

[0052] (V PN -V R2A ) / R tr2 =V R2A / R tr2 +V R2A / R2···(2)

[0053] Next, turn on switch SW0, relative to the negative bus ML. -A DC voltage VDC from power supply S2 is applied to ground E. Then, the voltage V across current sensing resistor R1 is measured. R1B And the voltage V across the current sensing resistor R2 R2B .

[0054] When the motor 1 experiences insulation degradation, the voltage of the DC power supply S2 is applied to the semiconductor switching element TR4 through the motor's insulation resistance Rm1. Furthermore, current flows to the current sensing resistor R1 and the semiconductor switching element TR4.

[0055] Similarly, when the motor 2 has insulation degradation, the voltage of the DC power supply S2 is applied to the semiconductor switching element TR10 through the insulation resistance Rm2 of the motor. Moreover, the current flows to the current sensing resistor R2 and the semiconductor switching element TR10.

[0056] In addition, the voltage across the smoothing capacitors C1 and C2 is the DC voltage V of the inverter. PN Current is applied to semiconductor switching elements TR1 and TR4. Therefore, current flows from semiconductor switching element TR1 to TR4. Additionally, current also flows to the current sensing resistor R1.

[0057] Similarly, current flows from the semiconductor switching element TR7 to TR10. Additionally, current also flows to the current sensing resistor R2.

[0058] The currents flowing from semiconductor switching elements TR1 to TR4 and from TR7 to TR10 mentioned above are the leakage currents of these semiconductor switching elements. However, the leakage currents of these semiconductor switching elements are generally smaller than the current flowing due to the reduction in the insulation resistance of the motor. Therefore, it can be inferred that the voltages of the smoothing capacitors C1 and C2 will not decrease significantly.

[0059] At this point, the following formulas (3) and (4) hold true.

[0060] (V PN -V R1B ) / R tr1 +(VDC-V R1B ) / Rm1=V R1B / R tr1 +V R1B / R1···(3)

[0061] (V PN -V R2B ) / R tr2 +(VDC-V R2B ) / Rm2=V R2B / R tr2 +V R2B / R2···(4)

[0062] The insulation resistance Rm1 of motor 1 can be calculated by solving the simultaneous equations of formula (1) and formula (3) as follows.

[0063] Rm1=R1(VDC-V R1B (V) PN -2V R1A ) / {(V R1B -V R1A V PN}···(5)

[0064] Furthermore, the insulation resistance Rm2 of motor 2 can be obtained by solving the simultaneous equations of formulas (2) and (4) as follows.

[0065] Rm2=R2(VDC-V R2B (V) PN -2V R2A ) / {(V R2B -V R2A V PN}···(6)

[0066] The above calculations are performed by the detection control units 41 and 42. Alternatively, the calculations can also be performed by detecting the voltage V of each of the current sensing resistors R1 and R2. R1A V R2A Calculate the insulation resistance values ​​Rm1 and Rm2. Alternatively, multiple measurements of the two voltages V can be used. R1A V R2A The various average values ​​of any one or both parties.

[0067] Using these average values ​​not only reduces the impact of outliers caused by noise, but also yields more accurate insulation resistance values ​​Rm1 and Rm2.

[0068] Furthermore, the calculated insulation resistance values ​​Rm1 and Rm2 are transmitted to the user equipment as information. The transmission of the insulation resistance values ​​Rm1 and Rm2 can be achieved by any means. For example, these resistance values ​​can be transmitted via wired or wireless communication.

[0069] Users who know the insulation resistance values ​​Rm1 and Rm2 can determine that insulation resistance degradation has occurred when these values ​​are low. Furthermore, based on predictions of grounding failures in the motor system, motors can be replaced in advance, thus preventing such accidents from happening.

[0070] Whether the insulation resistance has deteriorated can be determined using appropriate methods. For example, it can be determined by comparing it with values ​​known from experiments or experience, with the initial values ​​measured, recorded, or stored when the motor control device was first set up using a normal product, or with setting values ​​other than safety benchmarks.

[0071] The insulation resistances Rm1 and Rm2 of motors 1 and 2 are very small. Furthermore, when the semiconductor switching elements TR4-TR6 and TR10-TR12 on the negative side of semiconductor switching elements TR1-TR12 are short-circuited and fail, current flows from the DC power supply S2 through the deteriorated insulation of motors 1 and 2 to the semiconductor switching elements TR4-TR6 and TR10-TR12 on the negative side. However, the current capacity of the DC power supply S2 is very small compared to the smoothing capacitors C1 and C2. Therefore, the current flowing through it can be controlled to a very small value.

[0072] Therefore, there is no risk of secondary damage to the semiconductor switching elements TR4~TR6 and TR10~TR12 on the negative side, and consequently, there is no risk of insulation degradation in motors 1 and 2.

[0073] The above description illustrates the method of the present invention in a 2-axis motor control device using two motors 1 and 2. However, the present invention can also be applied to devices with 1 axis or 3 or more axes. Even in the case of 3 or more axes, the method is the same as described above, except that a DC power supply S2 is provided only on the 1 axis.

[0074] The above method uses a three-phase AC power supply S1 as the first power supply unit. However, the first power supply unit can be either a single-phase AC power supply or a three-phase AC power supply. Furthermore, the above method uses a rectifier circuit as the DC supply unit. However, a power regenerable circuit such as a PWM converter can also be used. In this case, measurements are taken after the PWM converter is stopped.

[0075] Furthermore, instead of AC power, DC power sources such as batteries can be used as the primary power source. Additionally, electromagnetic contactors may not be used. Switches can also be used. Furthermore, when powering the motor control device from a battery, the contacts or terminals electrically connected during battery installation can be considered as the primary switch.

[0076] When using a DC power source such as a battery as the primary power source, and the DC power source itself is not grounded, a first switch is not required in principle. In this case, the voltage of the DC power source, the voltage of the smoothing capacitor, and the DC voltage supplied to the inverter composed of semiconductor switching elements are basically the same.

[0077] Furthermore, in the above-described method, the motor control devices Cont1 and Cont2 use a three-phase inverter composed of semiconductor switching elements. However, when driving a single-phase motor, a single-phase inverter can also be used. Additionally, the inverter type is not limited to the above-described method. The method can also be a full-bridge or half-bridge inverter.

[0078] Next, as a second aspect of the present invention, the method of using a bootstrap power supply will be described.

[0079] like Figure 2 As shown, this method is applicable when the gate drive power supply of the semiconductor switching elements TR1~TR3 and TR7~TR9 on the positive side of the inverter is composed of a bootstrap power supply B.

[0080] The bootstrap power supply B, which serves as the gate drive power supply for the semiconductor switching elements TR1 to TR3 on the positive side of the motor control device Cont1, uses the gate drive power supply (third power supply section) S3, resistor Rb, diode Db, and capacitor Cb provided for the semiconductor switching elements TR4 to TR6 on the negative side, to form the gate drive power supply for the semiconductor switching elements TR1 to TR3 on the positive side.

[0081] By switching the negative-side semiconductor switching elements TR4 to TR6 on and off, the gate drive power supply S3 for the negative-side semiconductor switching elements charges the capacitor Cb through resistor Rb and diode Db. This provides the gate drive power supply for driving the gates of the positive-side semiconductor switching elements TR1 to TR3.

[0082] Furthermore, the motor control device Cont2 is configured similarly. A gate drive power supply S3, a resistor Rb, a diode Db, and a capacitor Cb, provided for the negative-side semiconductor switching elements TR10 to TR12, constitute the gate drive power supply for the positive-side semiconductor switching elements TR7 to TR9. The operation of the gate drive power supply is the same as that of the motor control device Cont1.

[0083] In the motor control device Cont1 of this method, a switch SW1 for disconnecting the power supply is provided between a bootstrap power supply B used for the gate drive power supply of the semiconductor switching elements TR1 to TR3 (which are on the positive side) and a gate drive power supply S3 used for the semiconductor switching elements TR4 to TR6 (which are on the negative side) that provides power to them.

[0084] Similarly, in the motor control device Cont2, a switch SW2 is provided to disconnect the power supply in a manner that is between a bootstrap power supply B used for the gate drive power supply of the semiconductor switching elements TR7 to TR9 (which are on the positive side) and a gate drive power supply S3 used for the semiconductor switching elements TR10 to TR12 (which are on the negative side) that provides power to them.

[0085] During normal motor control, with switch SW0 open and SW1 and SW2 closed, electromagnetic contactor MS is activated. Furthermore, an inverter composed of semiconductor switching elements TR1 to TR12 drives motors 1 and 2 on each axis.

[0086] During insulation resistance testing, the entire shaft motor control operation stops. Semiconductor switching elements TR1 to TR12 are disconnected. Furthermore, electromagnetic contactor MS is disconnected. Switches SW1 and SW2 are disconnected. Additionally, the DC voltage V of the inverter, which is equal to the voltage across the smoothing capacitor C, is measured. PN The voltage V across the current sensing resistor R1 R1A and the voltage V across the current sensing resistor R2 R2A .

[0087] The voltage across the smoothing capacitor C is applied to the semiconductor switching elements TR1 to TR12 that constitute the inverter. Therefore, current flows from semiconductor switching element TR1 to TR4. Additionally, current flows to the current sensing resistor R1. Similarly, current flows from semiconductor switching element TR7 to TR10. Furthermore, current flows to the current sensing resistor R2.

[0088] The current flowing from semiconductor switching element TR1 to TR4, and the current flowing from semiconductor switching element TR7 to TR10, are the leakage currents of the aforementioned semiconductor switching elements.

[0089] Switches SW1 and SW2 are open. Therefore, current will not flow from the gate drive power supply S3 used by the negative-side semiconductor switching elements TR4-TR6 and TR10-TR12 through the bootstrap power supply B resistor Rb, diode Db and capacitor Cb to the current sensing resistors R1 and R2 used for insulation resistance detection.

[0090] Next, turn on switch SW0, relative to the negative bus ML. - A DC voltage VDC from power supply S2 is applied to ground E. Furthermore, the voltage V across current sensing resistor R1 is measured. R1B and the voltage V across the current sensing resistor R2 R2B .

[0091] When the motor 1 has insulation deterioration, the voltage VDC of the DC power supply S2 is applied to the semiconductor switching element TR4 on the negative side through the insulation resistance Rm1 of the motor, and the current flows to the current detection resistor R1 and the semiconductor switching element TR4 on the negative side.

[0092] Similarly, when the motor 2 has insulation degradation, the voltage VDC of the DC power supply S2 is applied to the negative-side semiconductor switching element TR10 through the motor's insulation resistance Rm2. Furthermore, current flows to the current sensing resistor R2 and the negative-side semiconductor switching element TR10.

[0093] In addition, the voltage V of the smoothing capacitor C PN Current is applied to semiconductor switching elements TR1 to TR12. Therefore, while current flows from semiconductor switching element TR1 to TR4, current also flows to current sensing resistor R1. Similarly, while current flows from semiconductor switching element TR7 to TR10, current also flows to current sensing resistor R2.

[0094] The current flowing from semiconductor switching element TR1 to TR4 and from TR7 to TR10 mentioned above are the leakage currents of the aforementioned semiconductor switching elements.

[0095] However, the leakage current from semiconductor switching element TR1 to TR4 and from TR7 to TR10 is 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 does not decrease significantly. From the above measurement results, the insulation resistances Rm1 and Rm2 of motors 1 and 2 can be calculated from the above formulas (5) and (6), similar to the above embodiment 1 of the present invention.

[0096] Alternatively, switches SW1 and SW2 are inserted in positions where all three phases are simultaneously switched on and off. However, the gate drive power supply can also be configured to allow switches SW1 and SW2 to be inserted into any phase.

[0097] Furthermore, this method illustrates the case where both motor control devices Cont1 and Cont2 are bootstrap power supplies B. However, when motor control device Cont2 is a bootstrap power supply B and the gate power supply of motor control device Cont1 is a normal insulated power supply, insulation resistance can still be detected without the need for switch SW1.

[0098] Next, as a third aspect of the present invention, the method of using a high-voltage IC drive power supply will be described.

[0099] like Figure 3 As shown, the present invention in this manner is applied to the case where gate control signals of semiconductor switching elements TR1-TR3 and TR7-TR9 on the positive side of the inverter are transmitted via a high-voltage IC.

[0100] In normal motor control, with switch SW0 open and SW1 and SW2 closed, electromagnetic contactor MS is closed. Furthermore, an inverter composed of switching elements TR1 to TR12 drives motors 1 and 2 on each axis.

[0101] During insulation resistance testing, the entire shaft motor control operation stops. Semiconductor switching elements TR1 to TR12 are disconnected. Furthermore, electromagnetic contactor MS is disconnected. Switches SW1 and SW2 are disconnected. Additionally, the DC voltage V of the inverter, which is equal to the voltage across the smoothing capacitor C, is measured. PNThe voltage V across the current sensing resistor R1 R1A And the voltage V across the current sensing resistor R2 R2A .

[0102] The voltage of the smoothing capacitor C is applied to the semiconductor switching elements TR1 to TR12 that constitute the inverter. Therefore, current flows from the semiconductor switching element TR1 to TR4. In addition, current flows to the current sensing resistor R1.

[0103] The same current flows from semiconductor switching element TR7 to TR10. Additionally, current flows to current sensing resistor R2. The current flowing from semiconductor switching element TR1 to TR4 and from TR7 to TR10 are the leakage currents of the aforementioned semiconductor switching elements.

[0104] Switches SW1 and SW2 are open. Therefore, current will not flow from the gate drive power supply S3 used by the negative-side semiconductor switching elements TR4-TR6 and TR10-TR12 through the power supply of the high-voltage IC to the current sensing resistors R1 and R2 used for insulation resistance detection.

[0105] Then switch SW0 is turned on. Furthermore, relative to the negative busbar ML... - A DC voltage VDC from power supply S2 is applied to ground E. Furthermore, the voltage V across current sensing resistor R1 is measured. R1B And the voltage V across the current sensing resistor R2 R2B .

[0106] Based on the above measurement results, the insulation resistances Rm1 and Rm2 of motor 1 and motor 2 can be calculated using the formulas (5) and (6) of the first and second methods of the present invention.

[0107] Alternatively, switches SW1 and SW2 are inserted in positions where all three phases are simultaneously turned on / off. However, the gate drive power supply of a high-voltage IC can also be configured to allow switches SW1 and SW2 to be inserted into any phase.

[0108] The bootstrap power supply and the high-voltage IC can be used in combination. In this case, similar to methods 2 and 3, switches SW1 and SW2 are used to disconnect the connection path from the gate drive power supply to both the bootstrap power supply and the high-voltage IC. This allows the insulation resistance Rm1 and Rm2 of motors 1 and 2 to be detected.

[0109] Of course, as a gate drive power supply, it can be combined and applied with switching elements used in conventional isolated power supplies.

[0110] The various embodiments of the present invention have been described above. However, the scope of the present invention is not limited to the specific embodiments described. All embodiments included in the claims are also included in this description. Furthermore, the terms and descriptions are not intended to limit the scope of the claims.

[0111] The detailed description has been given for illustrative and explanatory purposes. Many variations and modifications are possible in accordance with the teachings above. The detailed description is not without omissions or intended to limit the subject matter described herein. Although the subject matter has been described in words with particular structural features and / or methodological processes, it should be understood that the subject matter defined in the claims is not necessarily limited to the specific features or processes described. Rather, the specific features and processes described are illustrated as examples of implementing the claims.

Claims

1. A motor control device, characterized in that... include: First power supply section; The first switch can disconnect the power supply from the first power source. The DC power supply unit outputs power from the first power supply unit to the bus; A capacitor is connected to the busbar; A switching element converts the DC power supplied to the bus into AC power to drive and control the motor; The second power supply unit has one end connected to the busbar and the other end grounded via a second switch; The current detection unit detects the current value between the coil of the motor and the bus connected to the second power supply unit; as well as 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 power supply is disconnected by the first switch and when the second switch is open and closed, the voltage value held by the capacitor, and the voltage value generated by the second power supply unit.

2. A motor control device, characterized in that... include: The first power supply section is an ungrounded DC power supply; The DC power supply unit outputs power from the first power supply unit to the bus. A capacitor is connected to the busbar; A switching element converts the DC power supplied to the bus into AC power to drive and control the motor; The second power supply unit has one end connected to the busbar and the other end grounded via a second switch; The current detection unit detects the current value between the coil of the motor and the bus connected to the second power supply unit; as well as 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 second switch is open and closed, the voltage value held by the capacitor, and the voltage value generated by the second power supply unit.

3. The motor control device according to claim 1 or 2, characterized in that, At least one of the switching elements of the motor includes a bootstrap power supply. It is equipped with a third switch, which disconnects the power supply to the bootstrap power supply when the third switch is open. The current detection unit detects the current value when the third switch is turned off.

4. The motor control device according to claim 1 or 2, characterized in that, At least one of the switching elements of the motor includes a high-voltage IC for gate driving that transmits gate control signals. It is equipped with a third switch, which disconnects the power supply to the high-voltage IC when the third switch is open. When the third switch is turned off, the current detection unit calculates the current value for the at least one of the motors.

5. The motor control device according to claim 1 or 2, characterized in that, One end of the second power supply unit, either the negative or positive side, is connected to the busbar, and the other end is grounded. The voltage generated by the second power supply is set to be lower than the voltage maintained by the capacitor.

6. A method for detecting the insulation resistance of a motor control device, the motor control device comprising: First power supply section; The first switch can disconnect the power supply from the first power source; The DC power supply unit outputs power from the first power supply unit to the bus. A capacitor is connected to the busbar; as well as The switching element converts the DC power supplied to the bus into AC power to drive and control the motor. The insulation resistance detection method for the motor control device is characterized by comprising: The power supply is disconnected by the first switch. Disconnect the second switch of the second power supply unit, which is connected at one end to the busbar and at the other end to ground via a second switch. The current detection unit detects the first current value between the motor coil and the bus connected to the second power supply unit. Close the second switch. The current detection unit detects a second current value between the motor coil and the busbar connected to the second power supply unit. The insulation resistance value of the motor is calculated based on the detected first current value and second current value, the voltage value held by the capacitor and the voltage value generated by the second power supply unit.

7. A method for detecting the insulation resistance of a motor control device, the motor control device comprising: The first power supply section is an ungrounded DC power supply; The DC power supply unit outputs power from the first power supply unit to the bus. A capacitor is connected to the busbar; as well as The switching element converts the DC power supplied to the bus into AC power to drive and control the motor. The insulation resistance detection method for the motor control device is characterized by comprising: Disconnect the second switch of the second power supply unit, which is connected at one end to the busbar and at the other end to ground via a second switch. The current detection unit detects the first current value between the motor coil and the bus connected to the second power supply unit. Close the second switch. The current detection unit detects a second current value between the motor coil and the busbar connected to the second power supply unit. The insulation resistance value of the motor is calculated based on the detected first current value and second current value, the voltage value held by the capacitor and the voltage value generated by the second power supply unit.

8. The insulation resistance detection method for the motor control device according to claim 6 or 7, characterized in that, The motor control device further comprises: the switching element having at least one bootstrap power supply; and a third switch that disconnects the power supply to the bootstrap power supply when disconnected. When the third switch is turned off, the process of detecting the first current value and the process of detecting the second current value are performed.

9. The insulation resistance detection method for the motor control device according to claim 6 or 7, characterized in that, The motor control device further includes: the switching element having at least one high-voltage IC that transmits gate control signals and drives the gate; and a third switch that disconnects the power supply to the high-voltage IC when disconnected. When the third switch is turned off, the process of detecting the first current value and the process of detecting the second current value are performed.

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