the circuit of the multifunctional protector for electric motor(4)

Published:2011/7/7 6:28:00 Author:Ariel Wang | Keyword: multifunctional protector, electric motor | From:SeekIC

the working principle of the circuitSee as the chart above.The input voltage detecting circuit consists of the resistors RI～R3 and the varistors RV1～RV3.It is the balanced three phase circuit .When the three phase AC power supply is normal,the potential of the common point(A point) is 0V.When any phase of voltage in three phase AC power supply is abnormal(the voltage is too high or phase failure),the potencial of the common point rises.It conducts the in-circuit of the solid state relay KN.The coil in AC contactor KM is short-circuit.KM is released.It cuts off the input voltage.So it protects the electric motor.



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