Patent ID: 9581647
Date: 2017-02-28
CPC Classifications: G01R,H02H,H02P

Claim:
1. A motor drive comprising: an AC/DC conversion unit configured to convert alternating current (AC) voltage supplied from an AC power source to direct current (DC) voltage; an electromagnetic connector configured to perform switching to connect or disconnect the AC power source to or from said AC/DC conversion unit; a DC link unit configured to smooth the DC voltage outputted from said AC/DC conversion unit; a DC/AC conversion unit configured to convert the DC voltage smoothed by said DC link unit to AC voltage for driving the motor; a current detection unit configured for detecting current input from the AC power source to said AC/DC conversion unit, and a control unit configured to output a command to connect or disconnect said electromagnetic connector and control said AC/DC conversion unit, wherein said control unit includes: a time measurement unit configured to measure elapsed time since said electromagnetic connector performs the switching; and a welding judgment unit configured to judge that said electromagnetic connector is welded, in a case where the current measured by said current detection unit when said control unit outputs the command to connect the AC power source to said AC/DC conversion unit, after the predetermined time has elapsed since said control unit outputs the command to disconnect the AC power source from said AC/DC conversion unit, is less than a predetermined current level.