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zero sequence current protection with ultilizing third harmo

2016-09-11 07:07  
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zero sequence current protection with ultilizing third harmonic pressure velocity saturation circuit
The shown circuit is suitable for △ or Y-shaped connection of the three-phase motor with rather great capacity. Off phase is to adopt a speed differential current transformer saturation TA, whose primary side is connected to the main circuit in series and secondary side’s head and tail is connected in series to form the open triangle. At the moment that the three-phase supply current (equal) is symmetrical, third harmonic voltage generated by TA is gone through the rectifier VC and the filtering capacitor C. So the sensitive K relay takes action to drive the motor M to run normally. When there is one phase is off, the remaining two-phase’s line current is with contrasting phase. And their synthetic current is zero for releasing the K and disconnecting the main circuit of the motor.