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the circuit of loss-of-phase protecting relay for electric m

2016-09-25 07:15  
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the circuit of loss-of-phase protecting relay for electric motor (5)
When starting button is pressed,the voltage between L2 and L3 go to AC contactor KM through Stop button 51,start push button 52 ,the normally-closed contact of relay K and contact of thermal relay KR.KM pulls in.The electric motor gets to work.It provides 12V DC voltage for relay-driven circuit(consist of V1,V2,VD2 and K) after it is reduced by T,commutated by VD3 and filtered by C2. At the same time,it lights up VL.When three-phase (L1,L2,L3) AC voltage is normal,the voltage is 0V between the plus terminal of VD1 (the Y-connected middle point) and zero line N.V1 is not conducted with V2.K is released.