... equipment include :rectification transformer,alternating contactor,rectification two-electrode valve,direct current contactor,time relay,discharge resistance,RK-SWB ... .When we turn on the lifing switch,direct current contactor KM1,KM3 closed,transformer secondary winding and supply alternating ... When we turn on the droping switch ,direct current contactor KM1,KM3 release,the coil of the magnet will ...