A medium voltage inverter system comprising: a first rectifying unit configured to rectify an AC voltage provided through an input terminal to a DC voltage; a smoothing unit configured to smooth the DC voltage rectified by the first rectifying unit, the smoothing unit including a capacitor; and an inverter unit configured to convert the DC voltage smoothed by the smoothing unit to a predetermined AC voltage and to output the AC voltage to a motor through an output terminal, the system characterized by: a controller configured to control short-circuit of contact points of a Magnetic Contactor at the output terminal of the inverter unit when a failure at the input terminal occurs; a supply unit configured to supply an electric power to the controller; an auxiliary rectifying unit configured to rectify the AC voltage provided through the input terminal and to supply the rectified AC voltage to the supply unit; and an initial charging unit configured to charge the capacitor of the smoothing unit during an initial driving, wherein the supply unit is arranged to receive a voltage through the auxiliary rectifying unit when an inverter input voltage from the input terminal charges the capacitor via the initial charging unit, to receive a voltage from the capacitor at a DC terminal of the smoothing unit as a predetermined initial charging time elapses, to receive a voltage in response to potential difference through the auxiliary rectifying unit when the failure is generated, and to supply the electric power to the controller using a switching circuit. a first rectifying unit configured to rectify an AC voltage provided through an input terminal to a DC voltage; a smoothing unit configured to smooth the DC voltage rectified by the first rectifying unit, the smoothing unit including a capacitor; and an inverter unit configured to convert the DC voltage smoothed by the smoothing unit to a predetermined AC voltage and to output the AC voltage to a motor through an output terminal, the system characterized by: a controller configured to control short-circuit of contact points of a Magnetic Contactor at the output terminal of the inverter unit when a failure at the input terminal occurs; a supply unit configured to supply an electric power to the controller; an auxiliary rectifying unit configured to rectify the AC voltage provided through the input terminal and to supply the rectified AC voltage to the supply unit; and an initial charging unit configured to charge the capacitor of the smoothing unit during an initial driving, wherein the supply unit is arranged to receive a voltage through the auxiliary rectifying unit when an inverter input voltage from the input terminal charges the capacitor via the initial charging unit, to receive a voltage from the capacitor at a DC terminal of the smoothing unit as a predetermined initial charging time elapses, to receive a voltage in response to potential difference through the auxiliary rectifying unit when the failure is generated, and to supply the electric power to the controller using a switching circuit. a controller configured to control short-circuit of contact points of a Magnetic Contactor at the output terminal of the inverter unit when a failure at the input terminal occurs; a supply unit configured to supply an electric power to the controller; an auxiliary rectifying unit configured to rectify the AC voltage provided through the input terminal and to supply the rectified AC voltage to the supply unit; and an initial charging unit configured to charge the capacitor of the smoothing unit during an initial driving, wherein the supply unit is arranged to receive a voltage through the auxiliary rectifying unit when an inverter input voltage from the input terminal charges the capacitor via the initial charging unit, to receive a voltage from the capacitor at a DC terminal of the smoothing unit as a predetermined initial charging time elapses, to receive a voltage in response to potential difference through the auxiliary rectifying unit when the failure is generated, and to supply the electric power to the controller using a switching circuit.