Motor control device and method for detecting insulation resistance of motor control device

Abstract

The present application provides motor control device and motor control device insulation resistance detection method, the motor control device includes: current detection part, detect the winding and the negative side bus between the current value of motor; Insulation resistance calculation part, based on the current value and the voltage value of the capacitor connected with the bus and the voltage value of the second power supply part when the power supply is disconnected, and when the second switch connected to the second power supply part and the ground wire is opened and closed, and the current value detected by the current detection part, calculate the insulation resistance value of the motor; And leakage current protection part, detect to use the first switch to turn on the power supply and the second switch is in short circuit state, open the first switch.

Description

TECHNICAL FIELD

[0001] The present application relates to a motor control device and a method for detecting an insulation resistance of a motor control device. BACKGROUND

[0002] A motor such as a servo motor is driven by a motor control device including an inverter, and is used for a machine tool or the like. In a device in which a machine tool or the like performs machining using cutting fluid, the cutting fluid adheres to the motor. There is a problem in which the cutting fluid enters the inside of the motor and deteriorates the insulation of the motor.

[0003] Further, even when the motor is used other than for a machine tool, the motor can be deteriorated in insulation in a case of long-time use or in a case of a poor use environment.

[0004] The insulation of the motor is gradually deteriorated, and eventually the motor is grounded. If the motor is grounded, a leakage switch trips or the motor control device is broken. As a result, a system failure occurs. The system failure has a significant impact on a production line of a factory. Therefore, from the viewpoint of preventive maintenance, a device capable of detecting the insulation resistance of the motor is desired.

[0005] A method for detecting the insulation resistance of such a motor is described, for example, in Japanese Patent Laid-Open No. 2015-129704. The motor drive device described in Japanese Patent Laid-Open No. 2015-129704 has a rectification circuit, a power supply portion, an inverter portion, a current detection portion, a second switch, and an insulation resistance detection portion.

[0006] The rectification circuit rectifies an alternating voltage supplied from an alternating current power supply via a first switch into a direct current voltage. The power supply portion smoothes the direct current voltage rectified by the rectification circuit by a capacitor. The inverter portion converts the direct current voltage smoothed by the power supply portion into an alternating voltage by switching operation of a semiconductor switching element. The inverter portion drives a motor by the alternating voltage. The current detection portion measures a current value flowing through a resistor, one end of which is connected to a coil of the motor and the other end of which is connected to one terminal of the capacitor. The voltage detection portion measures a voltage value of both ends of the capacitor. The second switch grounds the other terminal of the capacitor. The insulation resistance detection portion detects an insulation resistance value of the motor as a resistance between the coil of the motor and the ground using two sets of current values and voltage values measured in two states, which are a state in which the operation of the motor is stopped and the first switch is turned off and the second switch is turned off, and a state in which the second switch is turned on.

[0007] Further, in Japanese Patent Laid-Open No. 2015-204709 ( Figure 1) and Japanese Patent Laid-Open No. 2015-129704, a motor driving device including an insulation resistance detection section that detects an insulation resistance value of a motor is described. In the motor driving device, a resistance is inserted between a second switch that can be grounded and a bus bar. Thereby, a current flowing between the second switch and the bus bar is limited. Thereby, certain protection against a failure caused by an overcurrent or the like is performed.

[0008] However, in the technology of Japanese Patent Laid-Open No. 2015-129704, in a case where normal motor driving is performed after the detection of the insulation resistance value of the motor ends, the second switch is turned off and the first switch is turned on, and the motor is driven by the inverter. At this time of motor driving, if the second switch is short-circuited and turned on, a current flows from the AC power source to the ground through the positive bus bar, and thus, an electric leakage occurs. The electric leakage becomes a cause of fire and electric shock, and thus, it is required to be suppressed.

[0009] In order to suppress the electric leakage, generally, a leakage switch is considered to be used. By providing the leakage switch at an input section of the AC power source, the leakage switch trips, and a current flowing from the AC power source to the ground can be blocked. However, in a structure in which the leakage switch is not provided as in Japanese Patent Laid-Open No. 2015-129704, it is difficult to block the electric leakage, and it is difficult to protect the electric leakage.

[0010] Further, in the structure described in Japanese Patent Laid-Open No. 2015-204709, a resistance is inserted between the second switch that can be grounded and the bus bar. Thereby, a current flowing between the second switch and the bus bar is limited. However, in a case where normal motor driving is performed, if the second switch is short-circuited and turned on, a current flows from the AC power source to the ground through the positive bus bar and the resistance. At this time, since the leakage current is limited by the resistance and becomes small, sometimes, the leakage current is smaller than a leakage detection value of a leakage switch provided at an input section of the AC power source. In this case, since the leakage switch does not trip, it is difficult to block a current flowing from the AC power source to the ground. SUMMARY

[0011] An object of the present application is to provide a motor control device and an insulation resistance detection method (control method) of the motor control device described below. The motor control device suppresses an electric leakage caused by a short-circuit failure of a ground switch that constitutes an insulation resistance detection circuit in a motor control device having an insulation resistance detection function without using a leakage switch, and thus, an insulation resistance of a motor can be detected with high accuracy.

[0012] The motor control device of one embodiment of the present application includes a first power supply portion; a first switch capable of interrupting power supply from the first power supply portion; a direct-current supply portion that outputs power from the first power supply portion to a bus; a capacitor connected to the bus; a switching element that converts a direct-current voltage supplied to the bus into an alternating-current voltage by which a motor is driven and controlled; a second switch one end of which is connected to a second power supply portion connected to the bus and the other end of which is capable of being grounded; a current detection portion that detects a current value between a winding of the motor and a negative bus; an insulation resistance calculation portion that calculates an insulation resistance value of the motor on the basis of current values respectively detected by the current detection portion when power supply is interrupted with the first switch and when the second switch is opened and closed, and a voltage value of the capacitor and a voltage value of the second power supply portion; and a leakage current protection portion that detects that power supply is turned on with the first switch and at least either the second switch or the third switch is in a short-circuit state, and interrupts the first switch.

[0013] Further, the motor control device of another embodiment includes a first power supply portion; a first switch capable of interrupting power supply from the first power supply portion; a direct-current supply portion that outputs power from the first power supply portion to a bus; a capacitor connected to the bus; a switching element that converts a direct-current voltage supplied to the bus into an alternating-current voltage by which a motor is driven and controlled; a ground capacitor one end of which is connected to a negative bus and the other end of which is grounded; a second switch one end of which is connected to a second power supply portion connected to the bus and the other end of which is capable of being grounded; a third switch that makes the negative bus capable of being grounded by being turned on for a predetermined time and discharges electric charge of the ground capacitor connected to the bus; an insulation resistance calculation portion that calculates an insulation resistance value of the motor on the basis of current values respectively detected by a current detection portion when power supply is interrupted with the first switch and when the second switch is opened and closed after the third switch is turned on for a predetermined time, and a voltage value of the capacitor and a voltage value of the second power supply portion; and a leakage current protection portion that detects that power supply is turned on with the first switch and at least either the second switch or the third switch is in a short-circuit state, and interrupts the first switch.

[0014] Further, another motor control device includes: a first power supply section; a first switch capable of interrupting power supply from the first power supply section; a direct current 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 a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled; a ground capacitor having one end connected to a negative side bus and the other end grounded; a second switch having one end capable of being grounded and the other end capable of being connected to a third switch; the third switch that selects either a first contact having the other end connected to a second power supply section connected to the bus or a second contact connected to the bus, and is capable of being connected to the other end of the second switch; an insulation resistance calculation section that, based on the power supply being interrupted by the first switch, the state of the second contact of the third switch being selected during a prescribed time period, the second switch being closed, the negative side bus being connected to a ground point to discharge a charge of the ground capacitor connected to the bus, and thereafter, in the state of the first contact of the third switch being selected, the current values detected by a current detection section when the second switch is opened and when the second switch is closed, and the voltage value of the capacitor and the voltage value of the second power supply section, calculates an insulation resistance value of the motor; and a leakage current protection section that detects that the power supply is closed by the first switch and the second switch is in a short-circuit state, and opens the first switch.

[0015] One embodiment of the present application is an insulation resistance detection method for a motor control device including: a first power supply section; a first switch capable of interrupting power supply from the first power supply section; a direct current supply section that outputs power from the first power supply section to a bus; a capacitor connected to the bus; and a switching element that converts a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled, the insulation resistance detection method including: interrupting power supply by the first switch; in a second power supply section having one end connected to the bus and the other end capable of being grounded via a second switch, opening the second switch, detecting a first current value between a winding of the motor and the bus to which the second power supply section is connected by a current detection section; closing the second switch, detecting a second current value between the winding of the motor and the bus to which the second power supply section is connected by the current detection section; based on the first current value and the second current value detected and the voltage value of the capacitor and the voltage value of the second power supply section, calculating an insulation resistance value of the motor; and when the second switch is detected to be short-circuited in a case where the first switch is closed to supply power after the insulation resistance value of the motor is calculated, opening the first switch.

[0016] Further, another way is an insulation resistance detection method of a motor control device including a first power supply section, a first switch capable of interrupting power supply from the first power supply section, a direct current 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 a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled, and a ground capacitor connected to a negative bus, the insulation resistance detection method of the motor control device including: interrupting power supply by the first switch; discharging a charge of the ground capacitor connected to the bus by turning on a third switch having one end connected to the bus and the other end capable of being grounded for a prescribed time; interrupting the second switch in a second power supply section having one end connected to the bus and the other end capable of being grounded, detecting a first current value between a winding of the motor and the bus to which the second power supply section is connected by a current detection section; turning on the second switch, detecting a second current value between the winding of the motor and the bus to which the second power supply section is connected by the current detection section; calculating an insulation resistance value of the motor based on the detected first and second current values and voltage values of the capacitor and the second power supply section; and when the second switch or the third switch is detected to be short-circuited in a case where the first switch is turned on to supply power after the insulation resistance value of the motor is calculated, interrupting the first switch.

[0017] Further, another way is an insulation resistance detection method of a motor control device including a first power supply section, a first switch capable of interrupting power supply from the first power supply section, a direct current 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 a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled, a ground capacitor connected to a negative side bus, a second switch having one end capable of being grounded and the other end capable of being connected to a third switch, and the third switch that selects either a first contact connected to the other end of a second power supply section having one end connected to the bus and the other end capable of being grounded via the second switch and a second contact connected to the bus, and is capable of being connected to the other end of the second switch, the insulation resistance detection method of the motor control device including interrupting power supply by the first switch, discharging a charge of the ground capacitor connected to the bus by grounding the bus for a prescribed time by making the second switch on and the third switch a state of being connected to the second contact, selecting the first contact of the third switch thereafter, interrupting the second switch in the second power supply section, detecting a first current value between a winding of the motor and the bus to which the second power supply section is connected by a current detection section, making the second switch on, detecting a second current value between the winding of the motor and the bus to which the second power supply section is connected by the current detection section, calculating an insulation resistance value of the motor based on the detected first and second current values and voltage values of the capacitor and the second power supply section, and when a short circuit of the second switch or the third switch is detected in a case where the first switch is made on to supply power after the insulation resistance value of the motor is calculated, interrupting the first switch.

[0018] Other ways of the present application are clear from the following description of embodiments of the ways for implementing the technology of the present application.

[0019] According to the present application, when calculating the insulation resistance value of the motor, the power supply is turned off by the first switch. Thereby, the power supply from the first power supply section is stopped. Also, in a state where the second switch is turned off, a leakage current flows through the switching element due to the voltage of the capacitor, and the first current value is detected by the current detection section. On the other hand, also in a state where the power supply from the first power supply section is stopped, in a case where the second switch is turned on, the second current value is detected by the current detection section, the second current value including most of the current through the winding of the motor due to the voltage of the second power supply section (the remaining part is a small leakage current of the switching element on the negative side). Based on the two current values, i.e., the first current value and the second current value, and the voltage values of the capacitor and the second power supply section, an operation is performed, whereby the insulation resistance value of the motor can be calculated with high precision.

[0020] After calculating the insulation resistance value of such a motor, in the motor control device, normal operation is performed. At this time, first, the first switch is turned on to supply power. At this time, due to welding or other reasons, a so-called short-circuit failure in which the second switch remains in the closed state sometimes occurs. In this case, the leakage current protection section, by detecting this situation, turns off the first switch, and stops the power supply to the motor control device.

[0021] Further, in this case, the "first switch" includes all switches including a breaker. Even if the "first switch" is a terminal or a contact that comes into contact with the terminal of the power supply, as long as it has a structure that can turn off the power supply from the power supply, it is all included. Further, as the "direct current supply section", a power converter or the like that converts alternating current power into direct current power is used. Further, the component called "switch" includes the "first switch" described above. The "switch" can be any switch as long as it can stop or flow the current. The "switch" also includes a mechanical switch, a relay, a semiconductor switch, and the like.

[0022] Further, in a case where a grounding capacitor is used, or the like, further provided are grounding switches as third switches in order to release the electric charge, in a case where a short-circuit failure occurs with respect to these grounding switches, it is also possible to cope in the same manner as in a case where a short-circuit failure of the second switch occurs.

[0023] As described above, according to the present application, in a motor control device that has an insulation resistance detection function, it is possible to suppress the leakage caused by a short-circuit failure of a grounding switch that constitutes an insulation resistance detection circuit, even without using a leakage switch. Therefore, it is possible to detect the insulation resistance of the motor with high precision.

[0024] Other actions and effects of the present application are clear from the description of the embodiments for implementing the technical means of the present application described later. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a circuit diagram of a motor control device of one embodiment of the present application.

[0026] Figure 2 is a circuit diagram of a motor control device of another embodiment of the present application.

[0027] Figure 3 is a circuit diagram of a motor control device of still another embodiment of the present application. DETAILED DESCRIPTION

[0028] In the following detailed description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments can be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing.

[0029] Figure 1 is a circuit diagram of a motor control device of one embodiment of the present application.

[0030] In addition, in the following description, current can include a current value, voltage can include a voltage value, impedance can include an impedance value, and further, resistance can include a resistance value. These terms are interpreted by technical common sense of a person skilled in the art.

[0031] First, a basic structure of a motor control device C ont1 will be described.

[0032] The motor control device C ont1 includes a rectifier circuit (direct current supply portion) S DC , a bus line ML including a positive side bus line ML + and a negative side bus line ML - , a smoothing capacitor (capacitor) Cl, an inverter including semiconductor switching elements TR1 to TR6, and an insulation resistance calculation portion 31.

[0033] A three-phase alternating current voltage is supplied from a three-phase alternating current power supply (first power supply portion) SI to the motor control device C ont1 via an electromagnetic contactor MS as a first switch capable of interrupting power supply. The motor control device C ont1 generates a direct current voltage by full-wave rectifying the three-phase alternating current voltage using a rectifier circuit (direct current supply portion) S DC , and outputs the direct current voltage to the bus line ML.

[0034] The output direct current voltage is smoothed by a smoothing capacitor (capacitor) Cl connected between the positive side bus line ML + and the negative side bus line ML - of the bus line ML.

[0035] Smoothed supply to bus bar ML + and ML - DC voltage supplied to bus bar ML + and ML - between the positive side and the negative side. The motor 1 is driven by an alternating current voltage obtained by inverting the DC voltage supplied to the bus bar ML + and ML - .

[0036] Motor control device C ont1 includes a DC power supply (second power supply) S2 as a DC power supply provided between the negative side bus bar ML - and the ground wire E, a second switch SW1 (second switch), a current detection resistance R1 connected to the negative side bus bar ML - and the winding L of the motor 1, and a detection control section (current detection section) 41. One end of the DC power supply S2 is connected to the negative side bus bar ML - , and the other end is grounded via the second switch SW1. The detection control section 41 detects the current from the voltage of the current detection resistance R1. Further, the detection control section 41 controls the detection operation of the insulation resistance and calculates the insulation resistance value.

[0037] The current detection resistance R1 is connected to the winding L of one of the U-phase, the V-phase, and the W-phase of the motor 1. The winding L of the motor 1 has a very small resistance, and thus can be detected in any phase.

[0038] The power supply used as the DC power supply S2 is a power supply having a voltage as high as possible in a range lower than the voltage of the smoothing capacitor C1, and is a power supply set so that the potential of the ground wire E side becomes a state higher than the negative side bus bar ML - . Further, a power supply having a small current capacity to the extent necessary for measurement is used as the DC power supply S2.

[0039] The reason for setting the voltage of the DC power supply S2 to be lower than the voltage of the smoothing capacitor C1 is as follows. That is, the reason is to suppress the flow of current from the insulation resistance R m1 of the motor 1 to the freewheeling diodes D f of the semiconductor switching elements TR1 to TR3 of the upper arm (positive side) of the inverter section in the direction of charging the smoothing capacitor C1, and to suppress the detection accuracy of the insulation resistance R m1 from being lowered.

[0040] The operation of the motor control device C ont1 will be described below.

[0041] In general motor control, the second switch SW1 is kept in an off state, and the electromagnetic contactor MS is turned on. Thus, motor control of each axis is performed by the inverter. In insulation resistance detection, the motor control device C ont1 Acts in the following manner.

[0042] The motor control operation is stopped, the semiconductor switching elements TR1 to TR6 are turned off, and the electromagnetic contactor MS is turned off. Next, the second switch SW1 is turned off, and the DC voltage V PN of the inverter and the voltage V R1A of the current detection resistor R1 are measured.

[0043] The voltage of the smoothing capacitor C1 is applied to the semiconductor switching elements TR1 to TR6 that constitute the inverter. Thus, the DC voltage V PN of the inverter is substantially equal to the voltage of the smoothing capacitor C1. By the above voltage, a current flows from the semiconductor switching element TR1 to TR4, and in addition, a current (first current (value)) flows through the current detection resistor R1.

[0044] The current flowing from the semiconductor switching element TR1 to TR4 on the positive side is a leakage current of the semiconductor switching element. In all phases, a leakage current also flows. By focusing on one phase to which the current detection resistor R1 is connected, the insulation resistance of the motor can be found.

[0045] If the equivalent leakage resistance of the semiconductor switching elements TR1 and TR4 is R tr1 , respectively, the following equation (1-1) holds.

[0046] (V PN -V R1A ) / R tr1 = V R1A / R tr1 + V R1A / R1 ··· (1-1)

[0047] Next, the second switch SW1 is turned on, and the voltage V - of the DC power supply S2 is applied between the negative bus line ML DC and the ground line E. In this state, the voltage V R1B of the current detection resistor R1 is measured. From these current detection resistor R1 and voltage V R1B , the current (second current (value)) flowing in the current detection resistor R1 can be found.

[0048] In the case where the motor 1 has insulation deterioration, the voltage of the DC power supply S2 is applied to the semiconductor switching element TR4 through the insulation resistance R m1 of the motor. Thus, a current flows through the current detection resistor R1 and the semiconductor switching element TR4.

[0049] In addition, the voltage of the smoothing capacitor Cl, that is, the direct current voltage V PN is applied to the semiconductor switching elements TRl, TR4. Therefore, the current flows from the semiconductor switching element TRl to TR4. In addition, the current also flows through the current detection resistor Rl.

[0050] These currents flowing from the semiconductor switching elements TRl to TR4 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 decrease in the insulation resistance of the motor. Therefore, it is conceivable that even with the leakage currents, the voltage of the smoothing capacitor Cl hardly decreases.

[0051] At this time, the following equation (2-1) is established.

[0052] (V PN -V R1B ) / R tr1 +(V DC -V R1B ) / R m1 =V R1B / R tr1 +V R1B / R1···(2-1)

[0053] The insulation resistance R m1 of the motor 1 can be found from the following equation by solving the simultaneous equations of the equation (1-1) and the equation (2-1).

[0054] R m1 = Rl (V DC -V R1B ) (V PN -2V R1A ) / {(V R1B -V R1A ) V PN} ··· (3-1)

[0055] These operations are performed by the detection control section 41. In addition, of course, the insulation resistance value R R1A can be calculated by detecting the voltage V m1 of the current detection resistor Rl. In connection with this, the voltage V R1A may also be measured a plurality of times, various averages of the measured voltages are adopted, and the insulation resistance value R m1 is calculated.

[0056] In the case of using such various averages, the influence of abnormal values due to noise and the like can be mitigated, and the insulation resistance value R m1 with higher precision can be obtained.

[0057] And, the calculated insulation resistance value R m1 is transmitted to the user device as information. The insulation resistance value R m1 may be transmitted by any means. The means for transmitting the insulation resistance value R m1 may be wired transmission or wireless transmission.

[0058] The user who knows the insulation resistance value R m1 can determine that the insulation resistance has deteriorated in the case where the above insulation resistance value is low, and can predict in advance that the motor is grounded and the system fails. Therefore, the user can suppress the occurrence of such an undesirable situation by taking measures such as replacing the motor in advance.

[0059] An appropriate determination method can be used to determine whether the insulation resistance has deteriorated. As the determination method, for example, a method of comparing with a value known from experiments or experience, a method of comparing with an initial value measured and recorded or stored when a normal product is used at the time of initially setting the motor control device, or a method of comparing with a safety reference and other set values can be used.

[0060] Sometimes the insulation resistance R m1 of the motor 1 is very small, and the semiconductor switching elements TR4 to TR6 on the negative side short-circuit and break down. In this case, current flows from the DC power supply S2 to the semiconductor switching elements TR4 to TR6 on the negative side through the insulation deteriorated portion of the motor 1. Here, the current capacity of the DC power supply S2 can be made very small compared to the smoothing capacitor C1. Therefore, the flowing current can be limited to a small current.

[0061] Therefore, the possibility of secondary breakdown of the semiconductor switching elements TR4 to TR6 on the negative side and further insulation deterioration of the motor 1 is small.

[0062] In the described mode, the case where the embodiment of the present application is applied to a motor control device using one shaft of a motor 1 is described. The embodiment of the present application can also be applied to a two-shaft or three-shaft or more motor control device. As described in the described mode, even if the motor control device is a two-shaft or more motor control device, the DC power supply S2 can be provided only to at least one shaft.

[0063] In the described mode, a three-phase AC power supply S1 is used as the first power supply portion. A single-phase AC power supply can also be used instead of the three-phase AC power supply as the first power supply portion. Further, in the described mode, a rectifier circuit is used as the DC supply portion. The DC supply portion can also be a circuit such as a PWM converter that can be regenerated as a power supply. In this case, the measurement is performed in a state where the PWM converter is stopped.

[0064] In addition, the power supply from the first power supply unit can be switched on and off not only by an electromagnetic contactor, but also by a switch.

[0065] Furthermore, in the aforementioned method, C serves as the motor control device. ont1 A three-phase inverter including semiconductor switching elements is used. In the case of driving a single-phase motor, it serves as the motor control device C. ont1 C ont2 Single-phase inverters can also be used. Furthermore, the inverter type is not limited to the methods described above; it can be a full-bridge inverter or a half-bridge inverter.

[0066] Furthermore, in this method, the gate drive power supply for the semiconductor switching elements TR1 to TR6 uses a conventional isolated power supply (not shown). Depending on the requirements, any gate drive power supply, such as a bootstrap power supply, a high-voltage IC, or a combination of other power supplies, can be selected.

[0067] Next, the leakage current protection unit 5, which constitutes the core of the embodiment of the present invention, will be described. This leakage current protection unit 5 is used to suppress leakage current caused by a short circuit fault in the grounding switch constituting the insulation resistance detection circuit.

[0068] like Figure 1 As shown, on the negative side busbar ML - A leakage current protection unit 5 is provided between the DC power supply S2 and the DC power supply S2.

[0069] Once the insulation resistance value calculation and testing are complete, the second switch SW1 is opened and the electromagnetic contactor MS, which acts as the first switch, is turned on for normal motor control. Then, motor control for each axis is performed via an inverter composed of semiconductor switching elements TR1 to TR6.

[0070] At this time, due to welding failure, equipment malfunction, or other reasons, the second switch SW1 may experience a short circuit fault. In this case, leakage current flows from the three-phase AC power supply S1 through the negative busbar ML. - Flowing towards ground line E.

[0071] If this leakage current increases, the equipment located in the energized path of the leakage current may malfunction. Therefore, in this embodiment, a leakage current protection unit 5 is provided.

[0072] The leakage current protection unit 5 includes: a current detection resistor R3, a leakage current detection unit 6, a power on / off detection unit 7, and an electromagnetic contactor control unit 8. The current detection resistor R3 is due to the negative bus ML... -The leakage current detection section 6 detects whether or not a current of a prescribed value or more flows through the second switch SWl. The leakage current detection section 6 detects the current flowing through the second switch SWl by detecting a drop voltage of the current detection resistor R3 interposed between the negative side bus line ML

[0073] The leakage current detection section 6 detects whether or not a current of a prescribed value or more flows through the second switch SWl. The leakage current detection section 6 detects the current flowing through the second switch SWl by detecting a drop voltage of the current detection resistor R3 interposed between the negative side bus line ML - The leakage current detection section 6 detects whether or not a current of a prescribed value or more flows through the second switch SWl. The leakage current detection section 6 detects the current flowing through the second switch SWl by detecting a drop voltage of the current detection resistor R3 interposed between the negative side bus line ML

[0074] The power-on detection section 7 detects whether or not the voltage of the three-phase alternating current power supply Sl is applied to the motor control device in the case where the electromagnetic contactor MS as the first switch is turned on, and outputs the application state of the voltage of the three-phase alternating current power supply Sl to the electromagnetic contactor control section 8.

[0075] The electromagnetic contactor control section 8 controls the turn-on and turn-off of the electromagnetic contactor MS on the basis of the output of the leakage current detection section 6 and the output of the power-on detection section 7.

[0076] In the case where the power-on detection section 7 detects the turn-on state of the electromagnetic contactor MS to which the voltage of the three-phase alternating current power supply Sl is applied and outputs and the leakage current detection section 6 detects the state in which the leakage current of a prescribed value or more flows and outputs, the electromagnetic contactor control section 8 judges that the leakage current caused by the short-circuit failure of the second switch SWl occurs, and promptly turns off the electromagnetic contactor MS.

[0077] In the present mode, the current detection resistor R3 is interposed between the negative side bus line ML - and the direct current power supply S2. However, irrespective of this, the setting position of the current detection resistor R3 can be any position as long as it is a position through which the leakage current flowing in the second switch SWl passes. The current detection resistor R3 can be set, for example, between the direct current power supply S2 and the ground line E.

[0078] In the present mode, the drop voltage of the current detection resistor R3 is used to detect the leakage current flowing in the second switch SWl. In connection with this, any current detection device can be used as long as it is a device such as a current detector using a Hall element that can detect the current approximately.

[0079] Further, the leakage current detection section 6 can detect whether or not a current of a prescribed value or more flows through the second switch SWl. As shown in the present mode, it is configured to detect the current flowing through the second switch SWl by detecting a drop voltage of the current detection resistor R3 interposed between the negative side bus line ML- The leakage current detection section 6 can detect the state of the leakage current by a circuit that is directly electrically connected without insulation, as with the leakage current detection section 6 that compares the drop voltage of the current detection resistor R3 that detects the leakage current between the direct current power supply S2 with the prescribed reference voltage Ref. Alternatively, the leakage current detection section 6 can be configured to transmit a signal for evaluating the leakage current value via a converter that can be insulated.

[0080] Figure 2 is a circuit diagram showing another mode of the motor control device to which the present application is applied.

[0081] In Figure 1 , the mode of the present application in a motor control device using one axis of one motor 1 is explained. Figure 2 shows an example of applying the present application to a motor control device using two axes of two motors 1, 2. Further, in Figure 2 , in order to cope with noise, the motor control device C ont1 , C ont2 has a negative bus line ML - grounded via a ground capacitor C3, C4, respectively. As for Figure 2 , the same parts as Figure 1 are simplified in explanation.

[0082] The motor control device C ont2 includes: a bus line ML including a positive bus line ML + and a negative bus line ML - , a smoothing capacitor (capacitor) C2, an inverter including semiconductor switching elements TR7 to TR 12 , and an insulation resistance calculation section 32.

[0083] A three-phase alternating current voltage is supplied from a three-phase alternating current power supply (first power supply section) S1 to the motor control device C ont2 via an electromagnetic contactor MS as a first switch that can interrupt the supply of electric power. The motor control device C ont2 generates a direct current voltage by performing full-wave rectification on the three-phase alternating current voltage using a rectification circuit (direct current supply section) S DC , and outputs the direct current voltage to the bus line ML.

[0084] The output direct current voltage is smoothed by the smoothing capacitor (capacitor) C2 connected between the positive bus line ML + and the negative bus line ML - of the bus line ML.

[0085] The motor control device C ont2 has substantially the same structure as the motor control device C ont1 .

[0086] From motor control device C ont1 rectifier circuit S DC To motor control device C ont2 DC voltage is supplied. Motor control device C ont2 The motor 2 is configured to be driven by an AC voltage, which is supplied by a semiconductor switching element TR7 to TR8. 12 The inverter is obtained by inversely transforming the DC voltage supplied to the bus ML.

[0087] Motor control device C ont1 C ont2 negative side busbar ML - To cope with noise, they are grounded via grounding capacitors C3 and C4 respectively.

[0088] Here, on the negative side busbar ML - A third switch SW2, which serves as a grounding switch, is also installed. One end of the third switch SW2 is connected to the negative busbar ML. - One end is connected, and the other end can be grounded.

[0089] Motor control device C ont2 The insulation resistance calculation unit 32 includes the negative side busbar ML in the busbar ML. - The current sensing resistor R2 and the detection control unit (current sensing unit) 42 are connected to the winding L of the motor 2. The detection control unit 42 detects the current based on the voltage across the current sensing resistor R2. In addition, the detection control unit 42 calculates the insulation resistance value.

[0090] The power supply used as DC power supply S2 is a power supply with the highest possible voltage within a range that is lower than the voltage of smoothing capacitors C1 and C2, and is set such that the potential of the ground wire E side is higher than that of the negative bus ML. - The power supply is in a high-voltage state. Furthermore, as a DC power supply S2, a power supply with a small current capacity required for measurement is used.

[0091] The reason for setting the voltage of DC power supply S2 to be lower than the voltage of smoothing capacitors C1 and C2 is as follows. Specifically, it is to suppress current from flowing from the insulation resistance R of motors 1 and 2 during measurement. m1 R m2 The freewheeling diodes D of the semiconductor switching elements TR1~TR3 and TR7~TR9 on the upper arm (front side) of the inverter section f The current flows in the direction that charges the smoothing capacitors C1 and C2, and suppresses the insulation resistance R. m1 R m2 The detection accuracy thus decreases.

[0092] The following describes the motor control device C.ont1 , C ont2 the operation.

[0093] In the normal motor control, the second switch SW1 and the third switch SW2 are kept in the off state, and the electromagnetic contactor MS is turned on. Thus, the motor control of each axis is performed by the inverter. In the insulation resistance detection, the motor control device C ont1 , C ont2 operates in the following manner.

[0094] The motor control operation of all axes is stopped, the semiconductor switching elements TR1 to TR 12 are turned off, and the electromagnetic contactor MS is turned off. Also, the second switch SW1 is kept in the off state, and the third switch SW2 is turned on. During a prescribed time period, the charges of the ground capacitors C3, C4 are discharged, and the potential difference between the negative bus and the ground line is made 0 V. Next, the third switch SW2 is turned off, and the direct current voltage V PN of the inverter, the voltage V R1A of the current detection resistor R1, and the voltage V R2A of the current detection resistor R2 are measured.

[0095] At this time, in the case where the motor control device C ont1 , C ont2 is a structure that does not have the ground capacitors C3, C4, the process of discharging the charges thereof can be omitted.

[0096] Since the voltage of the ground capacitors C3, C4 is 0 V, the current does not flow from the ground capacitors C3, C4 through the insulation resistances R m1 , R m2 of the motors 1, 2 to the measurement circuit.

[0097] The voltage of the smoothing capacitors C1, C2 is applied to the semiconductor switching elements TR1 to TR 12 that constitute the inverter. Thus, the direct current voltage V PN of the inverter is substantially equal to the voltage of the smoothing capacitors C1, C2. By the above voltage, the current flows from the semiconductor switching element TR1 to TR4, and in addition, the current (first current (value)) flows through the current detection resistor R1. Similarly, the current flows from the semiconductor switching element TR7 to TR 10 , and in addition, the current (first current (value)) flows through the current detection resistor R2.

[0098] The current flowing from the semiconductor switching element TR1 to TR4 on the positive side and the current flowing from the semiconductor switching element TR7 to TR 10 are the leakage currents of the semiconductor switching elements. In all phases, similarly, the leakage currents flow. By focusing on one phase to which the current detection resistors R1, R2 are connected, the insulation resistance of the motor can be found.

[0099] If the equivalent drain resistance of the semiconductor switching element TR1, TR4 is taken as R tr1 , respectively, and the equivalent drain resistance of the semiconductor switching elements TR7, TR 10 is taken as R tr2 , respectively, the following equations (1-1), (1-2) are established. In addition, equation (1-1) is the same as the above equation (1-1).

[0100] (V PN -V R1A ) / R tr1 = V R1A / R tr1 + V R1A / R1... (1-1)

[0101] (V PN -V R2A ) / R tr2 = V R2A / R tr2 + V R2A / R2... (1-2)

[0102] Next, the second switch SW1 is turned on, and the voltage V - of the direct-current power supply S2 is applied between the negative-side bus line ML DC and the ground line E. In this state, the voltage V R1B of the current detection resistance R1 and the voltage V R2B of the current detection resistance R2 are measured. From these current detection resistances R1, R2 and the voltages V R1B , V R2B , the current (second current (value)) flowing in the current detection resistances R1, R2 can be obtained.

[0103] In the case where the motor 1 has insulation deterioration, the voltage of the direct-current power supply S2 is applied to the semiconductor switching element TR4 through the insulation resistance R m1 of the motor. Therefore, the current flows through the current detection resistance R1 and the semiconductor switching element TR4.

[0104] Also, in the case where the motor 2 has insulation deterioration, the voltage of the direct-current power supply S2 is applied to the semiconductor switching element TR 10 through the insulation resistance R m2 of the motor. Therefore, the current flows through the current detection resistance R2 and the semiconductor switching element TR 10 .

[0105] In addition, the voltage of the smoothing capacitor C1, C2, that is, the direct-current voltage V PNThe voltage of the smoothing capacitor C2 is applied to the semiconductor switching element TR7. Therefore, current flows from the semiconductor switching element TR7 to TR4. In addition, current also flows through the current detection resistor R2.

[0106] Likewise, the voltage of the smoothing capacitor C2 is applied to the semiconductor switching element TR7. Therefore, current flows from the semiconductor switching element TR7 to TR4. In addition, current also flows through the current detection resistor R2. 10 In addition, current also flows through the current detection resistor R2.

[0107] These currents flowing from the semiconductor switching element TR1 to TR4 and from the semiconductor switching element TR7 to TR4 are the same as the currents flowing from the semiconductor switching element TR1 to TR4 and from the semiconductor switching element TR7 to TR4 in the above-described embodiment. 10 The currents flowing from the semiconductor switching elements TR1 and TR7 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 decrease in the insulation resistance of the motor. Therefore, it is conceivable that even with the leakage currents, the voltages of the smoothing capacitors C1 and C2 hardly decrease.

[0108] At this time, the following equations (2-1) and (2-2) are established. In addition, equation (2-1) is the same as the above-described equation (2-1).

[0109] (V PN - V R1B ) / R tr1 + (V DC - V R1B ) / R m1 = V R1B / R tr1 + V R1B / R1 ··· (2-1)

[0110] (V PN - V R2B ) / R tr2 + (V DC - V R2B ) / R m2 = V R2B / R tr2 + V R2B / R2 ··· (2-2)

[0111] The insulation resistance R m1 of the motor 1 can be found from the following equation by solving the simultaneous equations of the above-described equation (1-1) and equation (2-1). In addition, the following equation (3-1) is the same as the above-described equation (3-1).

[0112] R m1 = R1(V DC - V R1B )(V PN - 2V R1A ) / {(V R1B - V R1A )V PN} ··· (3-1)

[0113] In addition, the insulation resistance R of motor 2 m2 The following equation can be obtained by solving the simultaneous equations of equations (1-2) and (2-2).

[0114] R m2 =R2(V DC -V R2B (V) PN -2V R2A ) / {(V R2B -V R2A V PN}···(3-2)

[0115] These calculations are performed by the detection control units 41 and 42. Furthermore, it is possible to detect the voltage V across the current sensing resistors R1 and R2 respectively. R1A V R2A To calculate the insulation resistance value R m1 R m2 Relatedly, it is also possible to measure two voltages V multiple times. R1A V R2A Calculate the insulation resistance value R using the average values ​​of the measured voltages from either or both sides. m1 R m2 .

[0116] Using these various average values ​​can mitigate the impact of outliers caused by noise, etc., and yield a more accurate insulation resistance value R. m1 R m2 .

[0117] Sometimes the insulation resistance R of motors 1 and 2 m1 R m2 Very small, semiconductor switching elements TR1~TR 12 The negative-side semiconductor switching elements TR4~TR6, TR 10 ~TR 12 Short circuit failure. In this case, current flows from DC power supply S2 through the deteriorated insulation of motors 1 and 2 to the negative-side semiconductor switching elements TR4-TR6 and TR7. 10 ~TR 12 Flow. Here, the current capacity of the DC power supply S2 can be made very small compared to the smoothing capacitors C1 and C2. Therefore, the flowing current can be limited to a very small current.

[0118] Therefore, the negative-side semiconductor switching elements TR4~TR6 and TR are generated. 10 ~TR 12 The possibility of secondary damage and further insulation deterioration of motors 1 and 2 is small.

[0119] This embodiment describes the application of the invention to a two-axis motor control device using two motors 1 and 2. The embodiment of the invention can also be applied to motor control devices with three or more axes. As shown in this embodiment, even if the motor control device has three or more axes, the DC power supply S2 only needs to be provided on at least one axis.

[0120] Furthermore, in this method, C serves as the motor control device. ont1 C ont2 A three-phase inverter including semiconductor switching elements is used. In the case of driving a single-phase motor, it serves as the motor control device C. ont1 C ont2 Single-phase inverters can also be used. Furthermore, the inverter type is not limited to the methods described above; it can be a full-bridge inverter or a half-bridge inverter.

[0121] Furthermore, in the aforementioned method, TR1 to TR1 serve as semiconductor switching elements. 12 The gate drive power supply uses a conventional isolated power supply (not shown). Depending on the requirements, any combination of power supplies, such as a bootstrap power supply, a high-voltage IC, or other power supplies, can be selected for the gate drive power supply.

[0122] These structures can be found in motor control devices C. ont1 and motor control device C ont2 They are not shared in the same way. Furthermore, any method can be used as long as these structures are formed by combining different structures, etc., and the purpose of this invention can be achieved.

[0123] Next, it is explained that it is applied to Figure 2 The leakage current protection unit 5 shown in the motor control device is used to suppress leakage current caused by a short circuit fault in the grounding switch constituting the insulation resistance detection circuit (see reference). Figure 1 ).

[0124] exist Figure 1 In the motor control device shown, on the negative bus ML - A connection is provided between the DC power supply S2 and the DC power supply S2. Figure 1 The leakage current protection unit 5 is shown. In Figure 2 In the motor control device shown, except for the negative bus ML - In addition to the DC power supply S2, there is also the negative bus ML. - Another one is configured between the third switch SW2 and the third switch SW2. Figure 1 The leakage current protection unit 5 is shown. Here, it will be explained... Figure 2Structure and function of the leakage current protection section 5 in the illustrated motor control device. In the leakage current protection section 5, in a case where the power-on detection section 7 detects the on state of the electromagnetic contactor MS to which the voltage of the three-phase alternating current power source SI is applied and outputs and the leakage current detection section 6 of any one of the second switch SWl side or the third switch SW2 side detects the state where the leakage current of the prescribed value or more flows and outputs, the electromagnetic contactor control section 8 judges that the leakage current caused by the short-circuit failure of any one of the second switch SWl or the third switch SW2 occurs, and promptly turns off the electromagnetic contactor MS. In this case, the leakage current detection section 6 detects the short-circuit state of at least any one of the second switch SWl or the third switch SW2.

[0125] In Figure 2 the illustrated motor control device, the third switch SW2 for discharging the electric charge accumulated in the ground capacitors C3, C4 can also be protected from the leakage current.

[0126] Figure 3 Another mode of the motor control device to which the embodiment of the present application is applied is indicated.

[0127] Figure 3 The motor control device C ont1 and the motor control device C ont2 have the same basic structure as that of the mode illustrated in Figure 2 . However, they differ in that Figure 3 the mode illustrated adopts a composite (cooperative) switch of the second switch SWl and the third switch SW2. Here, the third switch SW2 is not configured as an on-off switch but as a selection switch. This selection switch can contact only any one of at least the contact point (second contact point) a that communicates with the direct current bus line ML - and the contact point (first contact point) b that communicates with the second power source S2.

[0128] The operation of the motor control device C ont1 , C ont2 in this case is described below.

[0129] In the normal motor control, the electromagnetic contactor MS is turned on in a state where the third switch SW2 is connected to the contact point a and the second switch SWl remains off. Thus, the motor control of each axis is performed by the inverter. At this time, the third switch SW2 remains in the state of being connected to the contact point a.

[0130] In the insulation resistance detection, the motor control device C ont1 , C ont2 operates in the following manner.

[0131] The motor control operation of the entire axle is stopped, and the semiconductor switching elements TR1 to TR 12 are turned off. The electromagnetic contactor MS is turned off, and the third switch SW2 is set to a state in which the contact a through which the negative-side bus line ML - is connected is selected. Further, by switching the second switch SW1 from off to on, a grounding circuit is constituted. Next, after a prescribed time, by switching the second switch SW1 from on to off, the grounding circuit is turned off. In this state, the voltage V PN of the current detection resistor R1 and the voltage V R1A of the current detection resistor R2 are measured. R2A

[0132] Next, the third switch SW2 is set to a state in which the contact b through which the second power supply unit S2 is connected is selected. Further, by switching the second switch SW1 from off to on, a grounding circuit is constituted. Next, the voltage V - of the direct-current power supply S2 is applied between the negative-side bus line ML DC and the ground line E. In this state, the voltage V R1B of the current detection resistor R1 and the voltage V R2B of the current detection resistor R2 are measured. From these current detection resistors R1, R2 and the voltages V R1B , V R2B , the current (second current (value)) flowing in the current detection resistors R1, R2 can be obtained.

[0133] The other operations and the measurement and calculation methods of the insulation resistances R m1 , R m2 of the motors 1, 2 are substantially the same as those of the motor control device of the above-described one of the embodiments of the application.

[0134] In the above-described each of the motor control devices of the embodiments of the application, the structures of the second switch SW1 and the third switch SW2 are different. These switches can be any structure as long as they are switches having the same technical meaning as the second switch SW1 and the third switch SW2. These switches can be switches that, when the insulation resistances R m1 , R m2 of the motors 1, 2 are measured, can discharge the charge accumulated in the grounding capacitors C3, C4 and perform current detection by application of the voltage V DC of the direct-current power supply S2.

[0135] Next, the leakage current protection unit 5 (refer to Figure 3 ) for suppressing the electric leakage caused by a short-circuit failure of the grounding switch that constitutes the insulation resistance detection circuit, which can be applied to the above-described one of the embodiments of the application, will be described. Figure 1 ​​

[0136] exist Figure 3 In the configuration shown, the second switch SW1 and the third switch SW2 are composite (cooperative) switches. To detect short-circuit faults in the second switch SW1, a short circuit is installed between the third switch SW2 and the second switch SW1. Figure 1 The leakage current protection unit 5 is shown.

[0137] Explanation applied to Figure 3 Leakage current protection unit 5 (see reference) of the motor control device shown Figure 1 The structure and function of the electromagnetic contactor MS are as follows: When the power supply detection unit 7 detects the on state of the electromagnetic contactor MS with the applied voltage of the three-phase AC power supply S1 and outputs an output, and the leakage current detection unit 6 of the leakage current protection unit 5 detects the state of leakage current flow exceeding the specified value and outputs an output, the electromagnetic contactor control unit 8 determines that a leakage current caused by the short circuit fault of the second switch SW1 has occurred, and quickly disconnects the electromagnetic contactor MS.

[0138] Additionally, leakage current protection unit 5 can be installed in the above. Figure 1 The position shown can be either between the second switch SW1 and the ground wire E, or it can be set at the position indicated.

[0139] The present invention has been described above in various ways. The scope of the present invention is not limited to what has been specifically specified in the description so far, but includes all methods encompassed by the matters set forth in the claims. Furthermore, the terms and descriptions do not limit the scope of the present invention.

[0140] Furthermore, the technology of the present invention particularly improves the protection function of the insulation resistance detection section of a motor control device when a short-circuit fault occurs in the grounding switch of the insulation resistance detection section, etc. In addition, the motor control device of the present invention can be implemented as a motor control device with a protection function of the insulation resistance detection section. Furthermore, the insulation resistance detection method of the motor control device of the present invention can also be implemented as a protection method or control method for the motor control device.

[0141] Furthermore, the insulation resistance detection method of the motor control device in this embodiment can be the following first method for detecting the insulation resistance of the motor control device.

[0142] The insulation resistance detection method of the first motor control device is a method for detecting the insulation resistance of 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 that outputs power from the first power supply unit to a bus; a capacitor connected to the bus; a switching element that converts the DC power supplied to the bus into AC power to drive and control the motor; and a grounding capacitor connected to the negative bus.

[0143] Further, the insulation resistance detection method of the first motor control device includes: for a second switch that is turned off by the first switch, one end of which is capable of being grounded and the other end of which is capable of being connected to a third switch, and the third switch that is capable of being connected to the other end of the second switch in either a state of being capable of selecting at least a first contact connected to the other end of a second power supply unit connected to the bus or a state of being connected to a second contact connected to the bus, turning on the second switch and making the third switch in a state of being connected to the second contact to ground the bus for a prescribed time, after discharging the charge of the ground capacitor connected to the bus, in a state where the first contact of the third switch is selected, making the other end of the second power supply unit capable of being grounded via the second switch, turning off the second switch, and detecting a first current value between the winding of the motor and the bus to which the second power supply unit is connected by a current detection unit;

[0144] turning on the second switch and detecting a second current value between the winding of the motor and the bus to which the second power supply unit is connected by the current detection unit;

[0145] calculating an insulation resistance value of the motor based on the detected first and second current values and voltage values of the capacitor and the second power supply unit; and

[0146] in a case where the first switch is turned on to supply power after calculating the insulation resistance value of the motor, when a short circuit of the second switch or the third switch is detected, turning off the first switch.

[0147] The detailed description has been given for the purpose of example and explanation. Many variations and alterations are possible in light of the above teachings. The detailed description is not meant to be limiting or to be exhaustive in the subject matter described herein. Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example implementations of the claims.

Claims

1. An electric motor control device characterized by comprising: a first power supply section; a first switch capable of interrupting power supply from the first power supply section; a direct current supply section outputting power from the first power supply section to a bus; a capacitor connected to the bus; a switching element converting a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled; a second switch having one end connected to a second power supply section connected to the bus and the other end capable of being grounded; a current detection section detecting a current value between a winding of the motor and a negative bus; an insulation resistance calculation section calculating an insulation resistance value of the motor based on current values respectively detected by the current detection section when the second switch is opened and when the second switch is closed, and a voltage value of the capacitor and a voltage value of the second power supply section, in a case where the power supply is interrupted by the first switch; and a leakage current protection section detecting that the power supply is turned on by the first switch and that at least either the second switch or the third switch is in a short-circuit state, and interrupting the first switch.

2. An electric motor control device characterized by comprising: a first power supply section; a first switch capable of interrupting power supply from the first power supply section; a direct current supply section outputting power from the first power supply section to a bus; a capacitor connected to the bus; a switching element converting a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled; a ground capacitor having one end connected to a negative bus and the other end grounded; a second switch having one end connected to a second power supply section connected to the bus and the other end capable of being grounded; a third switch capable of grounding the negative bus and discharging a charge of the ground capacitor connected to the bus by turning on for a prescribed time; an insulation resistance calculation section calculating an insulation resistance value of the motor based on current values respectively detected by a current detection section when the second switch is opened and when the second switch is closed after the power supply is interrupted by the first switch and the third switch is turned on for the prescribed time, and a voltage value of the capacitor and a voltage value of the second power supply section; and a leakage current protection section detecting that the power supply is turned on by the first switch and that at least either the second switch or the third switch is in a short-circuit state, and interrupting the first switch.

3. An electric motor control device characterized by comprising: a first power supply section; a first switch capable of interrupting power supply from the first power supply section; a direct current supply section outputting power from the first power supply section to a bus; a capacitor connected to the bus; a switching element converting a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled; a ground capacitor having one end connected to a negative bus and the other end grounded; a second switch having one end capable of being grounded and the other end capable of being connected to a third switch; the third switch selecting either a first contact having the other end connected to a second power supply section connected to the bus or a second contact connected to the bus, and capable of being connected to the other end of the second switch; The insulation resistance calculating section calculates an insulation resistance value of the motor, based on current values detected by the current detecting section when the second switch is opened and when the second switch is closed, and a voltage value of the capacitor and a voltage value of the second power supply section, in a state where the first contact of the third switch is selected after a charge of the ground capacitor connected to the bus is discharged by connecting the second contact of the third switch and turning on the second switch for a prescribed time after the power supply is turned off by the first switch. Further The leakage current protection section detects that the power supply is turned on by the first switch and the second switch is in a short-circuit state, and turns off the first switch.

4. The motor control device according to claim 2 or 3, characterized by The leakage current protection section is provided at least one of between the negative bus and the second power supply section, between the negative bus and the second switch, between the third switch and the second switch, and between the second switch and a portion where the second switch is provided.

5. The motor control device according to claim 2 or 3, wherein The leakage current protection section includes: a power supply turn-on detecting section that detects a turn-on state of the first switch; a leakage current detecting section that detects a short-circuit state of at least one of the second switch and the third switch; and an electromagnetic contactor control section that turns off the first switch based on outputs of the power supply turn-on detecting section and the leakage current detecting section.

6. The motor control device of claim 5, wherein The leakage current detecting section outputs a signal indicating that a leakage current is generated to the electromagnetic contactor control section when at least one of current values in a path where the leakage current flows is not zero or is larger than a prescribed value.

7. The motor control device of claim 5, wherein The leakage current detecting section determines whether the leakage current is generated based on a comparison between a drop voltage of a resistance that generates a drop voltage provided in a path where the leakage current flows and a prescribed reference voltage.

8. The motor control device of claim 7, wherein The resistance is provided at least one of between the negative bus and the second power supply section, between the negative bus and the second switch, between the third switch and the second switch, and between the second switch and a ground point.

9. The motor control device of claim 5, wherein The current value of the leakage current is transmitted to the leakage current detecting section via a converter.

10. An insulation resistance detecting method of a motor control device, the motor control device including: a first power supply section; a first switch that can turn off a power supply from the first power supply section; a direct current supply section that outputs power from the first power supply section to a bus; a capacitor connected to the bus; and a switching element that converts a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled, The insulation resistance detecting method of the motor control device includes: turning off the power supply by the first switch; turning off the second switch in a second power supply section in which one end is connected to the bus and the other end can be grounded via a second switch, and detecting a first current value between a winding of the motor and the bus to which the second power supply section is connected by a current detecting section; ​ the second switch is closed, and a second current value between the winding of the motor and the bus to which the second power supply unit is connected is detected by the current detection unit; based on the detected first and second current values and voltage values of the capacitor and the second power supply unit, an insulation resistance value of the motor is calculated; and in a case where the first switch is turned on to supply power after the insulation resistance value of the motor is calculated, the first switch is turned off when the second switch is detected to be short-circuited.

11. An insulation resistance detection method of a motor control device, characterized by, the motor control device includes: a first power supply unit; a first switch capable of turning off power supply from the first power supply unit; a direct current supply unit that outputs power from the first power supply unit to a bus; a capacitor connected to the bus; a switching element that converts a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled; and a ground capacitor connected to a negative side bus, the insulation resistance detection method of the motor control device includes: power supply is turned off by the first switch; a charge of the ground capacitor connected to the bus is discharged by turning on a third switch connected at one end to the bus and capable of being grounded for a predetermined time; a first current value between the winding of the motor and the bus to which the second power supply unit is connected is detected by a current detection unit in a second power supply unit connected at one end to the bus and capable of being grounded via a second switch; the second switch is closed, and a second current value between the winding of the motor and the bus to which the second power supply unit is connected is detected by the current detection unit; based on the detected first and second current values and voltage values of the capacitor and the second power supply unit, an insulation resistance value of the motor is calculated; and in a case where the first switch is turned on to supply power after the insulation resistance value of the motor is calculated, the first switch is turned off when the second switch or the third switch is detected to be short-circuited.

12. An insulation resistance detection method of a motor control device, characterized by, the motor control device includes: a first power supply unit; a first switch capable of turning off power supply from the first power supply unit; a direct current supply unit that outputs power from the first power supply unit to a bus; a capacitor connected to the bus; a switching element that converts a direct current voltage supplied to the bus into an alternating current voltage by which a motor is driven and controlled; a ground capacitor connected to a negative side bus; a second switch capable of being grounded at one end and connected at the other end to a third switch; and the third switch that selects either one of a first contact connected at one end to the bus and capable of being grounded via the second switch and a second contact connected to the bus, and is capable of being connected to the other end of the second switch, the insulation resistance detection method of the motor control device includes: power supply is turned off by the first switch; by making the second switch on and the third switch in a state of being connected to the second contact to ground the bus for a predetermined time, discharging the charge of the ground capacitor connected to the bus; thereafter selecting the first contact of the third switch; in the second power supply section, making the second switch off, detecting a first current value between the winding of the motor and the bus to which the second power supply section is connected by a current detection section; making the second switch on, detecting a second current value between the winding of the motor and the bus to which the second power supply section is connected by the current detection section; calculating an insulation resistance value of the motor based on the detected first and second current values and the voltage value of the capacitor and the voltage value of the second power supply section; and in a case where the first switch is made on to supply power after the insulation resistance value of the motor is calculated, when a short circuit of the second switch or the third switch is detected, making the first switch off.

13. The method of detecting the insulation resistance of a motor control device according to any one of claims 10 to 12, characterized by, the second power supply section is the capacitor charged with the bus, and the voltage value of the second power supply section is the voltage value of the capacitor.

14. The method of detecting the insulation resistance of a motor control device according to any one of claims 10 to 12, characterized by, the second power supply section is a direct current power supply section connected at one end to the bus, and the voltage value of the second power supply section is the voltage value outputted from the second power supply section.

15. The method of claim 14, wherein calculating the insulation resistance value includes calculating the insulation resistance value of the motor based on the current values respectively detected by the current detection section when the second switch is made off and when the second switch is made on and the voltage value of the capacitor and the voltage value of the direct current power supply section.

16. The insulation resistance detection method of the motor control device according to claim 14, wherein one end of a negative side of the direct current power supply section is connected to the negative side bus, the voltage outputted from the direct current power supply section is set to be lower than the voltage of the capacitor.

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