Power circuit of AC Circuit Breaker

The power circuit diagram of static AC Circuit Breaker is shown in the Figure. The control circuit is not given in this Figure. The SCR is used for ON and OFF of the circuit.

Working of AC Circuit Breaker

Positive half cycle

When switch S is ON, SCR receives gate pulse through control circuit path P – LOAD – D2 – R2 – R – SWITCH S – N. The SCR 1 is turned during positive half cycle of AC supply when switch S is in ON condition. The load current flows through path P – LOAD – SCR1 – N during positive half cycle of the AC supply. When the load current become zero, the SCR1 automatic turns off.

Negative half cycle

The SCR2 is turned ON during negative half cycle of the AC supply when switch S is in ON condition. The gate receives pulse through control circuit N – R1 – D1 – SWITCH S – R – LOAD – P. The load current flows through N – SCR2 – LOAD – P. Whenever it is necessary to break the circuit, switch S is kept open. There is no sparking at switch S because very low current flows through it.