MOTOR DRIVE DEVICE HAVING INSULATION DETERIORATION DETECTION FUNCTION AND MOTOR INSULATION RESISTANCE DETECTION METHOD

摘要

PROBLEM TO BE SOLVED: To solve a problem of a conventional motor drive device, in which the accuracy of insulation resistance measurement deteriorates due to a leakage current flowing via a semiconductor switching element of an inverter.SOLUTION: A motor drive device of the present invention includes: a rectifier circuit (3) that rectifies an AC voltage; a power supply unit (4) that smooths a DC voltage by a capacitor (41); an inverter unit (5) that converts the DC voltage into an AC voltage by a semiconductor switching element so as to drive a motor; a current detection unit (7) that measures the value of current flowing through a resistor (71) whose one end is connected to a coil of the motor and whose another end is connected to one terminal of the capacitor; a voltage detection unit (8) that measures a voltage value of the capacitor; a second switch (9) that grounds the other terminal of the capacitor; and an insulation resistance detection unit (10) that detects an insulation resistance value of the motor by using two pairs of current values and voltage values which are measured in two states where the second switch is turned off and where it is turned on.