JP2008228415A - Motor drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive unit which can prevent the abnormal overheating of a rush current suppression resistor by detecting the non-operation of a rush current suppression circuit, and is high in safety. <P>SOLUTION: The motor drive unit includes: the rush current suppression circuit 12 which is connected between positive electrodes of a converter 11 and a smoothing capacitor 13, and in which the rush current suppression resistor 12a and a switch 12b are connected in parallel with each other; a voltage detection circuit 16 connected to both ends of the rush current suppression circuit 12; a control circuit 15 which controls the switching of the switch 12b and the drive of the inverter 14 on the basis of a servo signal; and a logic circuit 17 which inputs the servo signal from the control circuit 15 and an output of the voltage detection circuit 16. The logic circuit 17 outputs an abnormality detection signal to the control circuit 15 from the logical sum of a voltage detected by the voltage detection circuit 16 and a servo-on signal, and the control circuit 15 stops the drive of the inverter 14. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor drive device that prevents abnormal heat generation of an inrush current suppression resistor and ensures safety when an inrush current suppression circuit becomes inoperative.

  In order to suppress the charging current flowing through the smoothing capacitor when the power is turned on, an inrush current suppression circuit including an inrush current suppression resistor and a switch may be installed in the power supply circuit of the motor drive device.

On the other hand, in order to prevent an excessive inrush current from flowing to the rectifier circuit when the power is turned on, a control circuit has been proposed that closes the current switching means for turning on / off the power supply to the rectifier circuit when the motor is driven. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 9-91832

  The problem to be solved by the invention is that if the circuit that suppresses the inrush current fails for some reason and the switch becomes inoperable, the motor drive current flows through the inrush current suppression resistor. This is where an unsafe condition occurs.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a highly safe motor driving device that can detect an inoperative operation of an inrush current suppression circuit and prevent abnormal overheating of an inrush current suppression resistor. And

  In order to solve the above problems, a motor drive device according to the present invention includes an inrush current suppression circuit connected between a DC power source and a positive electrode of a smoothing capacitor, and an inrush current suppression resistor and a switch connected in parallel, and the inrush current suppression circuit. A voltage detection circuit connected to both ends, a control circuit for controlling opening / closing of the switch and driving of the inverter unit based on a servo signal, and a logic circuit for inputting a servo signal from the control circuit and an output of the voltage detection circuit The logic circuit outputs an abnormality detection signal to the control circuit from the logical sum of the voltage detected by the voltage detection circuit and the servo-on signal, and the control circuit stops driving the inverter unit, Prevents inrush current suppression resistors from overheating and ensures safety.

  Further, in a motor drive device in which an inrush current suppression circuit in which a switch is connected in parallel to an inrush current suppression resistor is connected between the DC power source and the positive electrode of the smoothing capacitor, the switch is closed based on a servo-on signal instructing motor drive. And step 2 for detecting the voltage across the inrush current suppression resistor after step 1, and when the predetermined voltage drop is detected in step 2, the driving of the inverter unit is stopped to suppress the inrush current. An abnormality detection method for a motor drive device, characterized by protecting a resistor.

  According to the motor drive device of the present invention, when a predetermined voltage drop is detected between the terminals of the inrush current suppression circuit when the servo is turned on, it can be determined that the switch is malfunctioning. Burning of the vessel can be prevented.

  A motor drive device according to the present invention includes a converter unit that converts an AC power source into DC power, a smoothing capacitor that smoothes output power of the converter unit, and an inrush current suppression resistor provided between the converter unit and a positive electrode of the smoothing capacitor. And an inrush current suppression circuit in which switches are connected in parallel, a voltage detection circuit connected to both ends of the inrush current suppression circuit, a control circuit that controls opening and closing of the switch and driving of the inverter unit based on a servo signal, A logic circuit that inputs a servo signal from a control circuit and an output of the voltage detection circuit, and the logic circuit outputs an abnormality detection signal from the logical sum of a voltage detected by the voltage detection circuit and a servo-on signal. The control circuit servo-offs and stops the inverter unit to ensure safety.

  Hereinafter, specific examples will be described with reference to the drawings. FIG. 1 is a block diagram of a motor driving apparatus according to the present invention.

  In FIG. 1, a converter unit 11 converts an AC power source into DC power. The inrush current suppression circuit 12 connects the inrush current suppression resistor 12 a and the switch 12 b in parallel, and is provided between the converter unit 11 and the positive electrode of the smoothing capacitor 13. The inverter unit 14 is connected in parallel to the smoothing capacitor 13 and is switching-controlled by the control circuit 15 to drive the motor 18. Further, the control circuit 15 controls the drive so that the contact of the switch 12b is closed when the servo is on.

  The voltage detection circuit 16 is connected to both ends of the inrush current suppression circuit 12 to detect a voltage drop. The logic circuit 17 generates an abnormality detection signal from the logical sum of the voltage detected by the voltage detection circuit 16 and the servo-on signal, and outputs the abnormality detection signal to the control circuit 15.

  Here, a general operation will be described. First, since the smoothing capacitor 13 is charged via the inrush current suppression resistor 12a when the power is turned on, the charging current flows to the inrush current suppression resistor 12a. When it is detected by a voltage dividing resistor (not shown) that the terminal voltage of the smoothing capacitor 13 exceeds a predetermined value, the contact of the switch 12b is closed. Further, drive control is performed so that the switch 12b is opened below a predetermined value. Thereafter, a servo-on signal (motor drive signal) is input to the control circuit 15 from the host controller, and the inverter unit 14 is controlled to drive the motor 18.

  Since the motor drive device of the present invention uses a servo signal to detect an abnormality in the inrush current suppression circuit 12, even if the terminal voltage of the smoothing capacitor 13 exceeds a predetermined value, the switch 12b is not immediately closed, and the smoothing capacitor 13 The switch 12b is closed after the terminal voltage exceeds a predetermined value and the servo-on signal for driving the motor is waited (step 1).

  Further, the switch 12b is opened after waiting for the servo-off signal. That is, only the inrush current suppression resistor 12a is connected except when the servo is on.

  For this reason, when waiting for the servo-on signal after power-on, when the power failure is restored after a voltage drop due to a momentary power interruption or the like, the inrush current suppression resistor 12a suppresses the charging current of the smoothing capacitor 13. Works.

  If the inrush current suppression circuit 12 is normal when the servo is on, the motor drive current flows to the contact of the switch 12b, so the voltage drop detected by the voltage detection circuit 16 is a small value. On the other hand, when the switch 12b has an open failure, the motor drive current flows through the inrush current suppression resistor 12a, and thus the voltage drop detected by the voltage detection circuit 16 becomes a large value.

Therefore, the logic circuit 17 can output an abnormality detection signal to the control circuit 15 from the logical sum if the voltage detection circuit 16 detects a predetermined voltage value or more when the servo is on. When the control circuit 15 receives the abnormality detection signal, the control circuit 15 stops the drive of the inverter unit 14 and can prevent the inrush current suppression resistor 12a from generating heat (step 2).

  Further, the time until the smoothing capacitor 13 is fully charged is short, and if the voltage detection circuit 16 continues to detect a voltage drop for a certain time (time until the charging is completed) during servo-off, some abnormality occurs. Because it will be, it will display an alarm.

  The motor drive device of the present invention is useful for industrial applications in which at least a DC power supply is provided and the motor is driven and controlled.

1 is a configuration diagram of a motor control device according to a first embodiment of the present invention.

Explanation of symbols

11 DC power supply (converter part)
DESCRIPTION OF SYMBOLS 12 Inrush current suppression circuit 12a Inrush current suppression resistor 12b Switch 13 Smoothing capacitor 14 Inverter part 15 Control circuit 16 Voltage detection circuit 17 Logic circuit 18 Motor

Claims (2)

Based on the servo signal, an inrush current suppression circuit connected between the DC power supply and the positive electrode of the smoothing capacitor, an inrush current suppression resistor and a switch connected in parallel, a voltage detection circuit connected to both ends of the inrush current suppression circuit, A control circuit for controlling opening / closing of the switch and driving of the inverter unit; and a logic circuit for inputting a servo signal from the control circuit and an output of the voltage detection circuit, the logic circuit being detected by the voltage detection circuit An abnormality detection signal is output to the control circuit from the logical sum of the voltage and the servo-on signal, and the control circuit stops driving the inverter unit. In a motor drive device in which an inrush current suppression circuit having a switch connected in parallel to an inrush current suppression resistor is connected between the DC power supply and the positive electrode of the smoothing capacitor, the step of closing the switch based on a servo-on signal instructing motor drive; After step 1, there is provided step 2 for detecting the voltage across the inrush current suppression resistor. In step 2, when a predetermined voltage drop is detected, the driving of the inverter unit is stopped and the inrush current suppression resistor is detected. An abnormality detection method for a motor drive device characterized by protecting the motor.