A motor drive includes an electromagnetic connector for connecting an alternating current (AC) power source to an AC/DC conversion unit or disconnecting therefrom, a DC link unit, a DC/AC conversion unit for converting smoothed direct current voltage to AC voltage, a DC link voltage detection unit for measuring voltage of the DC link unit, and a control unit. The control unit includes a time measurement unit for measuring elapsed time since switching by the electromagnetic connector, and a welding judgment unit for judging that the electromagnetic connector is welded, provided that the difference between voltage between terminals of the DC link unit after charging the DC link unit and voltage between the terminals of the DC link unit after predetermined time has elapsed since disconnecting the AC power source from the AC/DC conversion unit, after the charge of the DC link unit, is less than a predetermined voltage level.