SOLUTION

Circuit breakers are mechanical devices designed to close or open contacts members, thus closing or opening of an electrical circuit under normal or abnormal conditions.

The main duty of the circuit breaker is

1. .It should carry the full load current continuously without overheating or damage
2. It should open and close the circuit on no load
3. It makes and breaks the normal operating current
4. It makes and breaks the short-circuit current of magnitude up to which it is designed for.
5. It must be capable of opening the faulty circuit and breaking the fault current.
6. It must be capable of carrying fault current for a short time while another circuit breaker is clearing the fault.