Patent ID: 7253639

Claim:
A method of detecting insulation resistance deterioration for a motor driven by a motor driver which comprises a power supply section in which electric power supplied from an AC power supply through a switch is rectified by a rectifier circuit and smoothed by a capacitor, and a motor driving amplifier in which a DC voltage from the power supply section is converted to an AC voltage to drive the motor, the method comprises: stopping the operation of the motor by turning the switch OFF, and then connecting one end of the capacitor to ground in conjunction with connecting the other end of the capacitor to a motor coil, after turning the switch OFF; detecting a current that flows through a closed circuit formed with the capacitor, motor coil, and ground, to detect insulation resistance deterioration of the motor; and carrying out said insulation resistance deterioration detection by latching a signal for detecting insulation resistance deterioration by means of a latch circuit when a voltage of a predetermined value is detected by voltage detection means for detecting the potential difference between both ends of said capacitor, after the output of the signal to turn OFF the switch connected to the motor driver.