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Circuit Breaker

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

a trigger.


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

circuit breakers.

The most general way of the classification of the circuit breaker is on

the basis of the medium of arc extinction. Such types of circuit breakers

are as follows :-

  1. Oil Circuit Breaker
    • Bulk Oil Circuit Breaker
    • Minimum Oil Circuit Breaker
  2. Minimum Circuit Breaker
  3. Air Blast Circuit Breaker
  4. Sulphur Hexafluoride Circuit Breaker
  5. Vacuum Circuit Breaker
  6. 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.


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