JP2012233826A5 - - Google Patents

Description

Motor control apparatus and motor insulation deterioration detection method

  The present invention relates to a motor control device provided with an insulation deterioration detection device for detecting motor insulation deterioration (abnormal decrease in insulation resistance) and a method for detecting motor insulation deterioration.

  The servo motor is driven by a motor control device including an inverter circuit that is PWM controlled. Among machine tools, in a machine tool that performs machining using a cutting fluid, the cutting fluid may adhere to the motor. Depending on the nature of the cutting fluid, there is a problem that the cutting fluid enters the motor and deteriorates the electrical insulation of the motor. The electrical insulation deterioration of the motor gradually proceeds and eventually leads to a ground fault. If the motor is grounded, the earth leakage breaker is tripped or the motor control device is damaged, and the system that uses the motor goes down. The system down has a great influence on the factory production line. Therefore, from the viewpoint of preventive maintenance, there is a need for an apparatus that can detect motor insulation deterioration.

As a conventional method for detecting such deterioration of motor insulation,
(1) Method using an electrical insulation resistance meter (2) A pair of DC input parts of an inverter circuit controlled by PWM, that is, a capacitor and a resistor between the positive electrode and the negative electrode, or either one of them and the ground (ground) A method for detecting insulation deterioration of a motor without stopping the driving of the motor by providing a circuit for detecting a potential difference between both ends of the resistor of the series circuit (Patent Document 1)
(3) The DC input part of the inverter circuit controlled by PWM is grounded (connected to the ground), and the DC voltage applied to the inverter device is applied to the motor using the semiconductor element included in the inverter circuit. Method of obtaining electric insulation resistance of motor by measuring DC voltage and DC current of inverter device (Patent Document 2)
(4) Insert a resistor and a switch between the negative pole of the PWM inverter connected to the power supply through the circuit breaker and the ground, and when the circuit breaker is open, close the switch and A method for obtaining a semiconductor switch of a pole from a voltage drop of the resistor by making the semiconductor switch conductive (Patent Document 3)
and so on.

Japanese Patent Laying-Open No. 2005-201669 JP-A-6-94762 JP 2009-204600 A

  The method of using the insulation resistance meter in (1) above is to measure the electrical insulation resistance by removing the wiring between the motor and the motor control device and connecting the insulation resistance meter between the motor winding and the ground (ground). The deterioration of insulation is detected by the value of electrical insulation resistance. However, with this method, there is a problem that the wiring of the motor must be removed and a large number of work steps are required.

  In the method (2), there is a problem that the current flowing through the detection circuit is affected by the leakage current flowing through the power supply, and an error occurs in the detection of the insulation deterioration.

  In the above method (3), the DC side of the inverter circuit is grounded (connected to the ground), and the DC voltage of the inverter device is applied to the motor using the semiconductor element in the inverter circuit. Then, the DC input voltage and DC input current of the inverter circuit at that time are measured to determine the electric insulation resistance of the motor. However, in this method, when the electric insulation of the motor deteriorates and a ground fault occurs, the DC voltage of the inverter circuit is short-circuited due to conduction of the semiconductor element in the inverter circuit. As a result, there is a problem that the semiconductor element is damaged. Also, a minute current flows through the detector that measures the direct current when insulation deterioration is detected, and a large current flows during normal motor control. For this reason, a current detector capable of flowing a large current and detecting a minute current with high accuracy is required. However, a general current detector cannot obtain such accuracy, and has a problem in increasing detection accuracy.

  In the method (4), when a capacitor is provided between the DC portion of the PWM inverter and the ground as a noise countermeasure, it takes time until the voltage of the insulation resistance detection resistor is stabilized by this capacitor. This is not a problem in an inverter circuit in which the power source of the positive polarity switch of the inverter circuit can always keep the semiconductor switch on. However, when the power supply of the positive polarity semiconductor switch of the inverter circuit is used with a capacitor and a diode in the upper stage of the inverter circuit as shown in FIG. 5 and the bootstrap circuit is used, the positive polarity power supply is turned on only for a short period of PWM operation. Therefore, there is a problem that the positive electrode semiconductor switch is turned off before the insulation resistance is detected and cannot be used. 5 is a self-excited inverter circuit, and drive signals (gate signals) of the transistors TR1 to TR6 constituting the semiconductor switch are drive circuits DC1 to DS6 provided for the transistor signals TR1 to TR6, respectively. Given by.

  The present invention has been made in order to solve the above-mentioned problems, and the purpose thereof is not to remove the wiring of the motor, and even if the motor is grounded, the semiconductor switch of the inverter circuit is not damaged. It is another object of the present invention to provide a motor control device having an insulation resistance detection function that can apply a bootstrap circuit to a drive circuit of a semiconductor switch and that is not affected by a leakage current from a power source.

  Another object of the present invention is not affected by leakage current due to switching of the inverter circuit, and even if the motor is grounded, the insulation switch of the motor is accurately degraded without damaging the semiconductor switch in the inverter circuit. It is an object of the present invention to provide a method for detecting an insulation deterioration of a motor capable of detecting the above.

  The motor control device of the present invention includes a rectifier circuit, an inverter circuit, and an insulation deterioration detection device. The rectifier circuit is connected to an AC power source via a circuit breaker and includes a smoothing capacitor between the positive DC output unit and the negative DC output unit. Further, the one or more inverter circuits are configured by connecting a pair of semiconductor switches in series, and a plurality of arm circuits in which a connection point of the pair of semiconductor switches serves as an AC output unit. The drive circuit of the upper semiconductor switch in the circuit is constituted by a bootstrap circuit, and applies a voltage to a plurality of excitation windings of one or more motors. The insulation deterioration detection device detects the insulation resistance of the motor driven by the inverter circuit and detects the deterioration of the insulation resistance.

  In the present invention, an insulation deterioration detection device including a voltage dividing circuit, a detection operation control unit, and an insulation resistance detection unit is used. The voltage dividing circuit is disposed between one of the positive DC output unit and the negative DC output unit and the ground via a normally open switch circuit. The detection operation control unit closes the normally open switch circuit when the circuit breaker is in the open state. In addition, the detection operation control unit turns on one of a pair of semiconductor switches in at least one arm circuit of the plurality of arm circuits, turns the other off, and turns off the other and turns on the other. Repeat the drive to the state with the same duty ratio, alternately apply positive voltage and negative voltage from the smoothing capacitor to at least one-phase excitation winding, and the lower semiconductor switch is the bootstrap circuit of the upper semiconductor switch A detection operation for setting the charge operation state when the switch is on is performed. The insulation resistance detection unit detects the insulation resistance based on the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit during the detection operation. Here, the “detection operation in which driving is repeated using a PWM signal having the same duty ratio” refers to a pair of semiconductor switches (upper stage) in at least one target arm circuit using a PWM signal with a constant pulse width. This means that one of the semiconductor switch and the lower semiconductor switch is turned on and the other is turned off, and thereafter, one of the switches is turned off and the other is turned on.

  According to the present invention, by performing such a detection operation, the semiconductor switch used in the upper stage of the inverter circuit and the lower semiconductor switch are driven and the voltage is applied to the excitation winding without rotating the motor. Therefore, it is possible to reliably detect the insulation resistance. In addition, when the lower semiconductor switch is in the ON state, the bootstrap circuit of the upper semiconductor switch is placed in the charge operation state, so that the bootstrap circuit can be used for the drive circuit of the upper semiconductor switch. .

  When a motor with reduced insulation resistance is detected, it is necessary to select a plurality of arm circuits in order to determine whether the insulation resistance is reduced due to any excitation winding. A pair of semiconductor switches included in the circuit is caused to perform a detection operation. In this way, it is possible to specify which phase of the excitation winding causes the insulation resistance to decrease.

  According to the present invention, the normal operation of the motor is stopped, the circuit breaker is turned off, the AC power supply is shut off, and the motor insulation resistance is detected. Therefore, the detection of the insulation resistance is not affected by the leakage current flowing through the power supply line or the power supply noise. In addition, since the insulation resistance is detected by using the divided voltage output from the voltage dividing circuit that is energized only when the insulation resistance is detected, the resistance for detecting the insulation resistance constituting the voltage dividing circuit has a dedicated resistance value. can do. In addition, when the insulation degradation is detected, the voltage divider circuit becomes a resistive load on the motor and the smoothing capacitor, so even if a ground fault occurs on the motor side, an overcurrent is quickly generated from the smoothing capacitor. Does not flow through the conducting semiconductor switch. Therefore, even when a ground fault occurs in the motor, the semiconductor switch in the inverter circuit can be prevented from being damaged. Note that the control power source required for operating the insulation deterioration detection device may be prepared separately from the power source to which the circuit breaker is connected, or by using a power circuit connected to the power source without going through the circuit breaker. Also good. Moreover, it is not necessary to remove the motor wiring in order to detect the insulation resistance, and no special man-hours are required.

In particular, according to the present invention, the voltage dividing circuit includes the other end of the first resistor whose one end is electrically connected to the negative DC output portion and the second end whose one end is electrically connected to the ground portion. What was comprised and electrically connected with the other end of the resistor can be used. In this case, the voltage across the first resistor is input to the insulation resistance detection unit as the divided voltage V _R1 , and the second resistor prevents overcurrent from flowing when the motor is in a ground fault state. It is preferable to use protective resistance. In this way, it is possible to reliably prevent an overcurrent from occurring when the motor is in a ground fault state. Moreover, it is preferable to arrange a normally open switch circuit between the other end of the first resistor and the other end of the second resistor. A normally open switch circuit may be provided between the second resistor and the ground.

The insulation resistance detection unit receives the divided voltage V _R1 and the inter-terminal voltage V _DC of the smoothing capacitor as inputs, sets the duty ratio to D%, sets the resistance value of the _first resistor to R ₁ , and sets the resistance value of the second resistor. When the resistance value is R ₂ , the insulation resistance R _M is
R _M = V _DC × (D / 100) × (R ₁ / V _R1 ) − (R ₁ + R ₂ )
It can comprise so that it may obtain | require by the computing equation of. Using this arithmetic expression, the insulation resistance can be obtained without removing the motor from the apparatus.

  When the inverter circuit is two or more inverter circuits respectively provided for two or more motors, the detection operation control unit can be configured as follows. In other words, it is possible to select a single inverter circuit to be detected from a plurality of inverter circuits, and to configure the detection operation control unit to perform a detection operation in the selected single inverter circuit. In this way, the insulation resistance of two or more motors can be detected using one voltage dividing circuit and one insulation resistance detector.

  Further, when the inverter circuit is three or more inverter circuits respectively provided for three or more motors, the detection operation control unit can be configured to perform the following operation. That is, multiple combinations of two inverter circuits are determined from three or more inverter circuits, two inverter circuits corresponding to the determined combinations are selected, and the two selected inverter circuits are detected simultaneously. Perform the action. Based on the parallel insulation resistance detected by the insulation resistance detection unit at that time, two inverter circuits including the inverter circuit that drives the motor whose insulation resistance is lowered are specified. Then, the detection operation is performed in each of the two specified inverter circuits. After the detection operation control unit performs the above-described operation, the insulation resistance detection unit may identify a motor having a reduced insulation resistance based on the detected insulation resistance.

In the motor insulation deterioration detection method of the present invention , the circuit breaker is first opened. Thereafter, a voltage dividing circuit is electrically connected between one of the positive DC output unit and the negative DC output unit and the ground. PWM with the same duty ratio for driving one of a pair of semiconductor switches in at least one of the arm circuits to be in an on state and the other to be in an off state, and then to turn one in an off state and the other in an on state Repeatedly using a signal, positive voltage and negative voltage are alternately applied to the at least one-phase excitation winding from the smoothing capacitor, and the bootstrap circuit of the upper semiconductor switch is charged when the lower semiconductor switch is on. The detection operation for setting the operation state is performed. Then, the insulation resistance of the motor is detected based on the divided voltage output from the voltage dividing circuit and the DC voltage input to the inverter circuit.

  When the inverter circuit is two or more inverter circuits respectively provided for two or more motors, one inverter circuit to be detected is selected from the two or more inverter circuits. If the detection operation is performed in one selected inverter circuit, it is possible to detect the deterioration of the insulation resistance of two or more motors.

  When the inverter circuit is three or more inverter circuits respectively provided for three or more motors, a plurality of combinations of two inverter circuits are determined from the three or more inverter circuits. Next, two inverter circuits respectively corresponding to the plurality of combinations determined are selected, and in the two selected inverter circuits, detection operations are simultaneously performed to detect parallel insulation resistance. Then, two inverter circuits including the inverter circuit that drives the motor whose parallel insulation resistance is lowered are specified. Thereafter, in each of the two specified inverter circuits, a detection operation is performed, and a motor having a reduced insulation resistance is identified based on the detected insulation resistance.

(A) is a circuit diagram which shows a structure of an example of embodiment of the motor control apparatus of this invention which drives one motor by one inverter circuit, (B) shows an example of the bootstrap circuit to be used. FIG. (A) thru | or (C) is a figure which shows the example of the PWM signal which made the duty ratio smaller than 100%, and made the pulse width constant. It is a circuit diagram which shows the structure of an example of 2nd Embodiment of the motor control apparatus of this invention which drives two motors with two inverter circuits. It is a circuit diagram which shows the structure of an example of 3rd Embodiment of the motor control apparatus of this invention which drives three motors by three inverter circuits. It is a figure which shows the example which used the bootstrap circuit for the drive circuit for driving the semiconductor switch used for the upper stage of an inverter circuit.

Embodiments for carrying out a motor control device and a motor insulation deterioration detection method of the present invention will be described below in detail with reference to the drawings. FIG. 1A is a diagram showing an example of a configuration of a motor control device 1 that drives one three-phase AC motor (motor) M by one inverter circuit 5, and FIG. 1B is an upper semiconductor switch described later. FIG. 6 is a diagram showing an example of a bootstrap circuit used for transistors TR1 to TR3 constituting the circuit. The motor control device 1 is connected to a three-phase AC power source AC through an electromagnetic contactor as a circuit breaker 2. In this motor control device 1, a three-phase AC output from a three-phase AC power source AC is full-wave rectified by a full-wave rectifier circuit 3 configured by six diodes D 1 to D 6 being bridge-connected to obtain a DC voltage. ing. The DC voltage is smoothed by a smoothing capacitor C made of an electrolytic capacitor. In the present embodiment, the full-wave rectifier circuit 3 and the smoothing capacitor C constitute a rectifier circuit. Both ends of the smoothing capacitor C constitute a positive DC output unit 4A and a negative DC output unit 4B.

The inverter circuit 5 includes a bridge circuit formed by connecting three arm circuits 51 to 53 in parallel. The three arm circuits 51 to 53 are configured by connecting a pair of semiconductor switches (TR1 and TR4, TR2 and TR5, TR3 and TR6) each including a transistor in series. Connection points CP1 to CP3 of the pair of semiconductor switches (TR1 and TR4, TR2, TR5, TR3, and TR6) serve as an AC output unit. Connected to the connection points CP1 to CP3 are star-connected three-phase excitation windings W1 to W2 of the motor M. FIG. 1 shows an electrical insulation resistance RM that gradually decreases due to electrical insulation deterioration of the motor between the neutral point of the star-connected three-phase excitation windings W1 to W2 and the ground (ground). It is shown. Diodes D are connected in antiparallel to the six transistors TR1 to TR6 used in the inverter circuit 5, respectively. In this embodiment, the inverter circuit 5 is PWM-controlled based on a PWM control signal output from a PWM control circuit 10 included in an inverter control circuit (not shown), and converts DC power into AC power and outputs it. The PWM control circuit 10 detects the position of the rotor of the motor M based on an output from a position detector such as an encoder (not shown) fixed to the output shaft of the motor M, and the motor M Performs rotor position and speed control. The upper transistors TR1 to TR3 are each provided with a bootstrap circuit BSC including a resistor R ₀ , a capacitor C ₀ , a diode D _0, and a DC power source DPS as typically shown in FIG. 1B. ing. Drive circuits DC1 and DC4 for supplying a PWM signal to the transistors are arranged at the bases of the transistors TR1 and TR4. The transistors TR2 and TR5 and the transistors TR3 and TR6 are also provided with a bootstrap circuit and a drive circuit similar to the configuration in FIG. In this bootstrap circuit BSC, the capacitor C ₀ is charged by the current flowing through the circuit of the DC power source DPS → resistance R ₀ → diode D ₀ → capacitor C ₀ → transistor TR 4 while the lower transistor TR 4 is conductive. As a result, the charge of the capacitor C _0, it is possible to raise the base-emitter voltage of the transistor TR1. Therefore, as described later, even after the circuit breaker 2 is opened, the conduction state of the upper transistors TR1 to TR3 can be secured by the PWM drive signal applied to the bases of the upper transistors TR1 to TR3 via the drive circuit DC1.

The motor control apparatus 1, insulation deterioration detection device 6 for detecting the electrical insulation deterioration of the motor M driven by the inverter circuit 5 (reduction in the insulation resistance R _M) is built. The insulation deterioration detection device 6 includes a voltage dividing circuit 7, a detection operation control unit 8, and an insulation resistance detection unit 9. The voltage divider circuit 7 is disposed between one of the negative DC output units 4B and the ground via a normally open switch circuit SW formed of a relay contact. Specifically, the voltage dividing circuit 7 has one end electrically connected to the ground and the other end of the first resistor R1 serving as an insulation deterioration detecting resistor whose one end is electrically connected to the negative electrode DC output unit 4B. Is connected to the other end of the second resistor R2, to which a normally open switch circuit SW that is normally open but is closed when a command is input is disposed. . The voltage across the first resistor R1 is input to the AD converter in the voltage comparator 9 as a divided voltage. The second resistor R2 constitutes a protective resistor having a resistance value that prevents an overcurrent from flowing when the motor M is in a ground fault state. By configuring the voltage dividing circuit 7 in this way, it is possible to reliably prevent an overcurrent from occurring when the motor M is in a ground fault state.

The detection operation control unit 8 closes the normally open switch circuit SW when the circuit breaker 2 made of an electromagnetic contactor is open. The detection operation control unit 8 performs the following detection operation. First, a pair of semiconductor switches in at least one arm circuit among the three arm circuits 51 to 53 (which will be described as a representative example of the arm circuit 51) (which will be described as a representative example of the transistors TR1 and TR4). One of these is turned on and the other is turned off, and then the drive of turning one on and the other on is repeated using a PWM signal having the same duty ratio. For example, an on / off operation is performed in which the transistor TR4 is turned off while the transistor TR1 is turned on, and the transistor TR1 is turned off while the transistor TR4 is turned on. By this on / off operation, a positive voltage and a negative voltage are alternately applied from the smoothing capacitor C to the one-phase excitation winding W1. Then perform a charging operation for charging the capacitor C ₀ when the bootstrap circuit BSC for upper transistor TR1, as described above the lower transistor TR4 is turned on.

“Repeating driving using a PWM signal having the same duty ratio” means that the duty ratio of a PWM signal used in performing PWM control is smaller than 100%, as illustrated in FIGS. 2A to 2C. Using the same PWM signal with a duty ratio (for example, 50%) and a constant pulse width, one of the target transistors TR1 and TR4 is turned on, the other is turned off, and then the other is turned off. This means that the drive to turn on the other is repeated using a PWM signal having the same duty ratio. As shown in the right diagram of FIG. 2, by using such a PWM signal, the average voltage applied to the excitation winding can be set to a voltage value corresponding to the duty. If the duty ratio is, for example, 60%, the transistor TR1 is turned on for a duty period of 60% (the transistor TR4 is turned off for this period), and the transistor TR4 is turned on for the remaining 40% duty period (the transistor TR1 is turned on for this period). Off state). The duty ratio is not particularly limited as long as the bootstrap circuit can be put into a charge operation state by a lower transistor and a voltage necessary for detecting the insulation resistance RM can be applied to the excitation winding. That is, the upper limit value of the duty ratio is preferably set to a value that allows the gate power supplies of the transistors TR1 to TR3 on the upper side of the inverter circuit 5 to be charged by, for example, a bootstrap circuit as shown in FIG. The lower limit of the duty ratio is preferably set to a value that can prevent the detection accuracy of the insulation resistance from being lowered even if the average voltage applied to the motor is lowered.

Then, during the detection operation, the insulation resistance detector 9 detects the insulation resistance based on the divided voltage output from the voltage divider circuit and the DC voltage input to the inverter circuit. The insulation resistance detector 9 includes an analog-digital converter AD and a central processing unit CPU. The analog-digital converter AD converts the divided voltage V _R1 output from the voltage dividing circuit 7 and the DC voltage (voltage between terminals of the smoothing capacitor) V _DC input to the inverter circuit 5 into digital data. The central processing unit CPU, according to the calculation formula to be described later to calculate the insulation resistance R _M.

The arithmetic expression to be used was determined as follows. The resistance value of the insulation resistance RM of the motor M and R _M First, the inter-terminal voltage of the smoothing capacitor and V _DC, the voltage across the first resistor R1 and V _R1, D% duty ratio, the first When the resistance value of the resistor R1 is R ₁ and the resistance value of the second resistor R2 is R ₂ , the voltage V _R1 across the first resistor R1 can be expressed by the following equation.

V _R1 = V _DC × (D / 100) / (R _M + R ₁ + R ₂ ) × R ₁
Here, the voltage drop of the inverter element is neglected as being small compared to V _DC . Insulation resistance R _M is
R _M = V _DC × (D / 100) × (R ₁ / V _R1 ) − (R ₁ + R ₂ )
It can be calculated by the following equation.

The calculation by the above calculation formula is executed by the central processing unit CPU. In the present embodiment, the central processing unit CPU monitors the detected insulation resistance, and generates an alarm to the user who uses the motor control device when the insulation resistance becomes a predetermined value or more. When an alarm occurs, the user replaces the motor if the insulation resistance is low, and prevents the motor from going down due to a ground fault. In the present embodiment, the pair of transistors TR1 and TR4 in at least one arm circuit in the arm circuits 51 to 53 are PWM-driven and turned on / off alternately. Specifically, one transistor such as a pair of transistors TR1 and TR4 that applies a voltage to each excitation winding is turned on with a 50% duty PWM signal, the other transistor is turned off, and then the other transistor is turned on. Is turned on with a PWM signal having a duty of 50%, and the driving for turning off one transistor is repeated. When a PWM signal with a duty of 50% is used, the absolute values of the positive voltage and the negative voltage applied to the exciting winding are equal, and both the detection of the insulation resistance and the charge operation of the bootstrap circuit can be executed in a balanced manner. it can.

  In the present embodiment, the transistor TR1 is a period in which a negative voltage is applied to the excitation winding W1 via the transistor TR4 after applying a positive voltage to the excitation winding W1 via the transistor TR1 and detecting an insulation resistance. The bootstrap circuit is charged. Next, after applying a positive voltage to the excitation winding W2 via the transistor TR3 and detecting an insulation resistance, a negative voltage is applied to the excitation winding W2 via the transistor TR6. Charge operation is performed. Thereafter, a positive voltage is applied to the excitation winding W3 via the transistor TR2 to detect the insulation resistance, and then the bootstrap circuit charge of the transistor TR2 is charged during a period in which a negative voltage is applied to the excitation winding W3 via the transistor TR5. Perform the action.

  The order in which the voltage is applied to the excitation winding specified by the detection operation control unit 8 is not limited to the present embodiment. The detection operation control unit 8 may simultaneously perform the same detection operation as described above on a plurality of excitation windings, apply a voltage to each excitation winding, and simultaneously detect the insulation resistance. .

  In the detection operation, when the PWM control circuit 10 receives a PWM signal generation command for the detection operation from the detection operation control unit 8, a predetermined duty is applied to the drive circuit of one of the pair of transistors in the designated arm. The PWM signal having a predetermined duty is applied to the other transistor drive circuit.

In the above embodiment, the insulation resistance is obtained by calculation using the above calculation formula. However, when detecting the insulation resistance, the present invention is not limited to using the above calculation formula. May be detected relatively. For example, when the insulation resistance R _M is high, the divided voltage V _R1 is low, and when the insulation resistance R _M is low, the divided voltage V _R1 is high. Therefore, the voltage corresponding to the _divided voltage V _R1 when the insulation resistance R _M is deteriorated to some extent is used as the voltage reference voltage Vref, and the divided resistance V _R1 is compared with the voltage reference voltage Vref, so that the insulation resistance R _M is relatively Can be detected automatically.

  The rectifier circuit 3 may be a circuit that can regenerate power to the three-phase AC power supply AC, such as a PWM converter. In that case, when detecting the insulation deterioration, the PWM converter is stopped and the insulation deterioration is detected.

  Note that the control power supply necessary for operating the insulation deterioration detection device 6 and the aforementioned DC power supply DPS are prepared separately from the three-phase AC power supply AC to which the circuit breaker 2 is connected. The control power supply may be configured to be connected to the three-phase AC power supply AC without going through the circuit breaker 2.

  FIG. 3 shows a circuit configuration of a second embodiment of the motor control device of the present invention. In the circuit configuration shown in FIG. 3, the number of 100 or 200 is added to the number of the reference numerals given to the members shown in FIG. 1 to the same members as the members constituting the circuit configuration shown in FIG. A detailed description will be omitted with reference to numerals. In the embodiment of FIG. 3, two inverter circuits 105 and 205 are connected to the full-wave rectifier circuit 103. Two motors M1 and M2 are connected to the two inverter circuits 105 and 205, respectively. In the present embodiment, the insulation resistance of two motors can be detected by using one insulation deterioration detecting device 106. Therefore, in this embodiment, when the circuit breaker 102 is in the open state, the normally open switch circuit SW is closed in the detection operation control unit 108 of the insulation deterioration detecting device 106 so that the two inverter circuits 105 and One inverter circuit to be detected is selected in order from 205, and the above-described detection operation is performed on a plurality of excitation windings in the selected inverter circuit.

Specifically, for example, the detection operation control unit 108 first sets the upper transistors of the pair of transistors (TR1 and TR4, TR2 and TR5, TR3 and TR6) included in the arms 151 to 153 of the inverter circuit 105 to 50%. detecting a resistance R _M1 of the insulation resistance RM1 period motor M1 which is turned on and a duty ratio, the charge operation of the bootstrap circuit of subsequent periods upper stage lower transistors are turned on state at a 50% duty ratio transistor I do. Next, the detection operation control unit 108 stops supplying the PWM signal to the transistors in the inverter circuit 105, and the pair of transistors (TR1 and TR4, TR2 and TR5, TR3 included in the arms 251 to 253 of the inverter circuit 205 are stopped. And TR6), the resistance RM2 of the insulation resistance RM2 of the motor _M2 is detected while the upper transistor is turned on at a duty ratio of 50%, and then the lower transistor is turned on at a duty ratio of 50%. The bootstrap circuit of the upper stage transistor is charged.

  If the same detection operation is executed in the inverter circuit corresponding to the remaining one motor after the determination of the insulation deterioration is completed by detecting the insulation resistance of one motor in this way, the order of the plurality of motors is changed. Insulation resistance can be detected at the same time, and it is possible to determine insulation deterioration in detecting insulation resistance of a plurality of motors at a reduced cost.

  FIG. 4 shows a circuit configuration of a third embodiment of the motor control device of the present invention. In the circuit configuration shown in FIG. 4, a number of 200 is added to the number of reference numerals attached to the members shown in FIG. 1 to the same members as those constituting the circuit shown in FIG. 1 (excluding the inverter circuit). A detailed description is omitted. In the embodiment of FIG. 4, four inverter circuits 105, 205, 305 and 405 are connected to the full-wave rectifier circuit 203. Four motors M1 to M4 are connected to the four inverter circuits 105 to 405, respectively. In this embodiment, it is possible to detect the insulation resistance of each of the four motors by using one insulation deterioration detection device 206 as in the embodiment of FIG. When detecting the insulation deterioration of the motors one by one, the detection operation control unit 208 of the insulation deterioration detection device 206 is closed when the circuit breaker 202 is in the open state, One inverter circuit to be detected is sequentially selected from the four inverter circuits 105 to 405, and the detection operation is performed in the selected one inverter circuit as in the embodiment of FIG.

More specifically, first detecting resistor R _M1 of the insulation resistance RM1 motor M1 driven by the inverter circuit 105, then it detects the resistance R _M2 of the insulation resistance RM2 motor M2 to be driven by an inverter circuit 205 , then detects the resistance R _M3 insulation resistance RM3 motor M3 is driven by the inverter circuit 305 may detect the resistance R _M4 of the insulation resistance RM4 motor M4 driven by the last inverter circuit 405.

  Instead of selecting inverter circuits one by one in this way, the detection operation control unit 208 may be configured to simultaneously select a plurality of inverter circuits and simultaneously detect the insulation resistance of the plurality of motors. Is possible. For example, two inverter circuits 105 and 205 are selected from the four inverter circuits 105 to 405 as the first combination. Then, the insulation resistances of the motors M1 and M2 driven by the two selected inverter circuits 105 and 205 (first combination) are detected. Next, the remaining two inverter circuits 305 and 405 (second combination) are selected. Then, the insulation resistances of the motors M3 and M4 driven by the remaining two inverter circuits 305 and 405 (second combination) are detected. According to the present embodiment, it is possible to sequentially detect the insulation deterioration of the motor by combining the two selected inverter circuits as one combination. If the number of inverter circuits selected at one time is the same, the configuration of the detection operation control unit 208 is simplified. In the case where the detection operation is performed with a plurality of inverter circuits as one combination at the same time, it can be understood that insulation deterioration has occurred in any one of the combinations. However, specifically, it is not immediately known which motor is causing the insulation deterioration. Therefore, the two inverter circuits that drive the motor having the deteriorated insulation resistance are individually the same as in the first embodiment. Thus, the insulation resistance may be detected to identify the motor in which insulation deterioration has occurred.

  When the number of inverter circuits cannot be divided into the same number of combinations, such as five, the number of inverter circuits to be selected may be changed instead of being fixed. That is, first, the detection operation may be performed for the first combination including three inverter circuits, and then the detection operation may be performed for the second combination including two inverter circuits.

  In order to identify a motor having a reduced insulation resistance among the four motors M1 to M4, a configuration in which the calculation result is returned to the detection operation control unit 208 by the central processing unit CPU as shown by a broken line in FIG. adopt. Then, the detection operation control unit 208 selects two appropriate inverter circuits from the plurality of inverter circuits, and simultaneously performs the detection operation using these inverter circuits.

That is, for each of the two inverter circuits, the PWM signal having the predetermined duty is applied to a pair of transistors in one arm circuit. In this way, the insulation resistance detector 209 detects the insulation resistance (parallel insulation resistance) in a state where the insulation resistances of the two motors driven by the two inverter circuits are connected in parallel. The central processing unit CPU calculates the parallel insulation resistance, and returns information specifying two inverter circuits whose parallel insulation resistance is greater than a predetermined reference value to the detection operation control unit 208. The detection operation control unit 208 that has obtained this information individually performs the detection operation for the specific two inverter circuits in the same manner as described above. Then, the central processing unit CPU calculates the insulation resistances of the two motors, respectively, and determines the deterioration of the insulation resistance. More specifically, first, the detection operation is simultaneously performed on the inverter circuits 105 and 205, the parallel insulation resistance of the motors M1 and M2 is detected, and then the detection operation in the inverter circuits 105 and 205 is stopped. Next, after performing the above-described detection operation in the inverter circuits 305 and 405 and detecting the parallel insulation resistance of the motors M3 and M4, the detection operation in the inverter circuits 305 and 405 is stopped. Next, when the parallel insulation resistance of the motors M1 and M2 is low, the detection operation of the inverter circuit 105 is performed to detect the insulation resistance of the motor M1, and then the detection operation in the inverter circuit 105 is stopped. Next, after detecting the inverter circuit 205 to detect the insulation resistance of the motor M2, the detecting operation in the inverter circuit 205 is stopped. When the motor M3 or M4 is out of order, a detection operation is performed on the inverter circuit 305, the insulation resistance of the motor M3 is detected, and then the detection operation in the inverter circuit 305 is stopped. Next, after detecting the inverter circuit 405 and detecting the insulation resistance of the motor M4, the detecting operation in the inverter circuit 405 is stopped. As a result, it is possible to efficiently detect the insulation deterioration of the four motors with one insulation resistance detector 209.

  In each of the above embodiments, the normal operation of the motor is stopped, the magnetic contactor is turned OFF, the three-phase AC power supply is shut off, and the motor insulation resistance is detected. For this reason, there is no influence of leakage current flowing through the power supply line or power supply noise. Further, since the insulation resistance is detected using the detection resistor that is energized only when the insulation resistance is detected, the insulation resistance detection resistor can be a resistor having a dedicated resistance value. Even if the motor is grounded, an excessive current does not flow because there is a protective resistance. Furthermore, according to each embodiment, it is not necessary to remove the wiring of the motor, and no special man-hours are required. Furthermore, in a motor control apparatus that drives a plurality of motors, it is only necessary to configure one insulation resistance detection unit for the plurality of motors, thereby reducing costs. Moreover, the insulation resistance of each motor can be detected by one insulation resistance detector. In addition, by devising the combination, even when there are many motors, it is possible to find a motor that has failed quickly. It is also possible to determine which phase of the motor is causing the insulation deterioration.

  In the above three embodiments, the voltage dividing resistor circuits 7 and 107 are connected to the negative DC output parts 4B and 104B when detecting the insulation resistance, but the voltage dividing resistor circuit is connected to the positive DC output parts 4A and 104A. 7 and 107 may be connected.

  In the above embodiment, the motor has star-connected three-phase excitation windings. However, the present invention can also be applied to detecting the insulation resistance of a motor having delta-connected three-phase excitation windings. Of course.

  According to the present invention, since the semiconductor switch used in the upper stage of the inverter circuit and the lower semiconductor switch are alternately driven to apply a voltage to the excitation winding without rotating the motor, the insulation resistance is reliably detected. be able to. In addition, when the lower semiconductor switch is in the ON state, the bootstrap circuit of the upper semiconductor switch is placed in the charge operation state, so that the bootstrap circuit can be used for the drive circuit of the upper semiconductor switch. .

DESCRIPTION OF SYMBOLS 1 Motor control device 2,102,202 Circuit breaker 3,103,203 Full wave rectifier circuit 4A, 104A, 204A Positive DC output part 4B, 104B, 204B Negative DC output part 5,105,205,305,405 Inverter circuit 6 , 106, 206 Insulation degradation detection device 7, 107, 207 Voltage divider circuit 8, 108, 208 Detection operation control unit 9, 109, 209 Insulation resistance detection unit 10, 110, 210 PWM control circuit TR1 to TR6 Transistor (semiconductor switch) )
D diode C smoothing capacitor R1 first resistor R2 second resistor SW normally open switch circuit