Patent ID: 9559580
Date: 2017-01-31
CPC Classifications: H02J,H02M,H02P

Claim:
1. An electric motor drive apparatus comprising: an AC/DC converter including a plurality of power devices, and converts AC voltage supplied from an AC power supply into DC voltage by switching of the plurality of power devices; a control circuit configured to perform PWM switching control of the plurality of power devices in accordance with switching commands; a current detecting circuit configured to detect input current from the AC power supply to the AC/DC converter; an electromagnetic contactor configured to connect or cut off the supply of power from the AC power supply to the AC/DC converter; and, a DC link unit including a smoothing capacitor for smoothing DC voltage output from the AC/DC converter; wherein the control circuit determines that the electromagnetic contactor has been welded when input current is detected in a condition where with the DC link unit having been charged, when the electromagnetic contactor is on, the electromagnetic contactor is turned off to cut off the supply of power from the AC power supply to the AC/DC converter and the plurality of power devices are controlled by PWM switching in accordance with the switching commands from the control circuit to test whether the input current from the AC power supply to the AC/DC converter increases when the electromagnetic contactor is cut off.