A circuit breaker is a switching device that interrupts the abnormal or fault
current. It is a mechanical device that disturbs the flow of high magnitude
(fault) current and in additions performs the function of a switch. The circuit
breaker is mainly designed for closing or opening of an electrical circuit,
thus protects the electrical system from damage.
Working Principle of Circuit Breaker
Circuit breaker essentially consists of fixed and moving contacts. These
contacts are touching each other and carrying the current under normal
conditions when the circuit is closed. When the circuit breaker is closed,
the current carrying contacts, called the electrodes, engaged each other
under the pressure of a spring.
During the normal operating condition, the arms of the circuit breaker
can be opened or closed for a switching and maintenance of the system.
To open the circuit breaker, only a pressure is required to be applied to
Whenever a fault occurs on any part of the system, the trip coil of the
breaker gets energized and the moving contacts are getting apart from
each other by some mechanism, thus opening the circuit.
Types of Circuit Breaker
Circuit breakers are mainly classified on the basis of rated voltages.
Circuit breakers below rated voltage of 1000V are known as the low
voltage circuit breakers and above 1000V are called the high voltage
The most general way of the classification of the circuit breaker is on
are as follows :-
- Oil Circuit Breaker
- Bulk Oil Circuit Breaker
- Minimum Oil Circuit Breaker
- Minimum Circuit Breaker
- Air Blast Circuit Breaker
- Sulphur Hexafluoride Circuit Breaker
- Vacuum Circuit Breaker
- Air Break Circuit Breaker
All high-voltage circuit breakers may be classified under two main
categories i.e oil circuit breakers and oil-less circuit breaker.