Motor driving apparatus

• US 20040257029A1
• Filed: 06/18/2004
• Published: 12/23/2004
• Est. Priority Date: 06/23/2003
• Status: Abandoned Application

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Yaeshima, Mamoru, Harada, Takashi, Sakamoto, Keiji, Ota, Naoto
• Application Number:
  US10/869,833
• Publication Number:
  US 20040257029A1
• Time in Patent Office: Days
• US Class Current: 318/802
• CPC Class Codes: G01R 31/343 in operation

Abstract

A motor driving apparatus capable of predicting motor insulation deterioration at low costs. When a motor drive amplifier is not in operation, a relay contact K1 is turned on or closed to form a closed circuit of a motor housing grounded at G2, a motor coil, resistors R1, R2, the relay contact K1, diodes D4, D5, D6, an AC power source, and a ground point G1. A voltage of the AC power source to ground is applied to the closed circuit. When the insulation resistance of the motor is high, a small current flows through the closed circuit, so that potential difference across the resistor R1 is small. If the motor insulation is deteriorated, a leakage current increases. If potential difference across the resistor R1 exceeds a reference voltage determined by a Zener diode, an output signal is output from a comparator, a signal is output from a photocoupler, and the decrease in insulation resistance is indicated on an indicator of a control unit. The motor insulation deterioration is predicted with ease at low costs, thus preventing a sudden stop of operation caused by a leakage of current, etc.

Claims

1. A motor driving apparatus for driving a motor using a grounded AC power source, comprising:

a motor driving unit for rectifying an alternating current from the grounded AC power source into a direct current and inverting the rectified direct current into an alternating current to drive the motor;

a detection resistor connected in series with a coil of the motor;

means for applying a DC voltage obtained by rectifying a voltage to ground of the AC power source to the coil of the motor through said detection resistor; and

a voltage detection circuit for detecting a voltage between terminals of said detection resistor when the DC voltage is applied.

2. A motor driving apparatus according to claim 1, further comprising a comparator for comparing the voltage detected by said voltage detection circuit with a reference value and means for outputting an abnormality signal when the detected voltage exceeds the reference value.

3. A motor driving apparatus according to claim 1, further comprising an A/D-converter for A/D-converting the voltage detected by said voltage detection circuit, wherein signals representing values of the AD-converted voltage are outputted to be displayed on a display device.

4. A motor driving apparatus according to claim 3, further comprising a memory for storing values of the A/D-converted voltage, wherein signals representing the values of the A/D-converted voltage stored in said memory are outputted to be displayed on the display device.

5. A motor driving apparatus according to claim 1, further comprising an A/D-converter for A/D-converting the voltage detected by said voltage detection circuit, wherein an abnormality signal is outputted when the AD-converted voltage exceeds a reference value.

6. A motor driving apparatus according to claim 5, further comprising a memory storing reference values preset for specifications of different motors or motor driving units and a microprocessor connected with said A/D-converter and said memory, wherein said microprocessor reads a reference value for a specification of the motor or the motor driving unit in use from said memory, compares the value of the A/D-converted voltage with the read reference value and outputs an abnormality signal when the value of the A/D-converted voltage exceeds the read reference value.

7. A motor driving apparatus according to claim 5, further comprising means for detecting the voltage to ground of the AC power source, a memory storing reference values preset for voltages to ground of different AC power sources, and a microprocessor connected with said A/D-converter and said memory, wherein said microprocessor reads a reference value for the detected voltage to ground of the AC power source, compares the value of the A/D-converted voltage with the read reference value and outputs an abnormality signal when the A/D-converted value exceeds the read reference value.

8. A motor driving apparatus according to claim 5, further comprising means for detecting the voltage to ground of the AC power source, a memory storing reference values preset for voltages to ground of different AC power sources and specifications of different motors or motor driving units, and a microprocessor connected with said A/D-converter and said memory, wherein said microprocessor reads a reference value for the detected voltage to ground of the AC power source and a specification of the motor or the motor driving circuit in use, compares the A/D-converted value with the read reference value and outputs an abnormality signal when the A/D-converted value exceeds the read reference value.

9. A motor driving apparatus according to claim 1, wherein said voltage detection circuit has a switch for enabling and disabling the voltage detection, and the voltage detection is enabled by said switch when the motor is not driven by the motor driving unit.