This product series works to step down three-phase AC power supply by transformer and then achieve DC 220Vvoltage through bridge commutating apparatus.The unit consists of auto air switch,transformer, two-phase or three -phase bridge rectifier assembly and AC contactor, The circuit configures short -circuit and over voltage protection devices. A rectiformer will be attached outside under handling capacity ofelectromagnet more than 19KW, while using single phase bridge commutating mode under handling capacity of electromagnet less than or equal to 4KW.