Three-phase motor phase-off over-current protection circuit

Published:2011/7/10 1:36:00 Author:Lucas | Keyword: VD5, Three-phase motor | From:SeekIC

The figure shows a rather practical circuit. When ST is pressed, KM pulls to start the motor M. The current transformer TA output current through the secondary side. The current forms a voltage signal through the VD1 rectifier and partial pressure by RP and R1. The voltage signal is added to the base VT1 through R2 and VD6. The other signal VT3 added to the base through RP. VT1, VT2 and VT3 form an emitter coupled bitable circuit. During the normal operation, VT1 ends and VT2 and VT3 are saturated to conduct. Then the relay K pulls to drive the motor M to run normally.



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