Working principle of Circuit Breaker(C.B)

A circuit breaker consists of two contacts - a fixed contact and moving contact.Under normal operating conditions,these contacts remain closed.But when a fault occurs,trip coil of C.B get activated and moving contact is pulled apart by a mechanism,thus opening the circuit.

Arcing Phenomenon

As soon as the moving contact is separated from fixed contact, an arc of current will be formed between the contacts.This arc is  quenched with  in short period of time so that circuit is braked completely.