Static DC Circuit Breaker

• The basic circuit for DC circuit breaker is shown in the figure A. 
• The SCR 1 is main SCR. When it is necessary to break load current, the SCR 1 is turned off.  
• There is no control circuit given in this figure for simplification. 
• When the SCR 1 is turned on, the load voltage becomes equal to supply voltage and charging of capacitor is done through path (+) V_dc – R1 – (+) C – C (-) – SCR 1 – V_dc (-). 
• The polarity of capacitor charging voltage is shown in the figure A.
• When it is require breaking load current, the SCR 2 is turned on. As soon as the SCR 2 is turned on, the SCR 1 is turned off due to reverse voltage across it. 
• The capacitor once again charge with reverse polarity through path (+) V_dc – LOAD – (+) C – C (-) – SCR 2 due to turned off of the SCR 1. 
• When voltage across capacitor reaches up to supply voltage, the load current becomes zero resulting SCR 2 is turned off.
•  The current passes through load resistance R1 becomes less than the holding current of the SCR 2.

STATIC DC CIRCUIT BREAKER DRAWING.PDF

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