Circuit Breaker Working Principle

Introduction Of Circuit Breaker :

A circuit breaker is an equipment which is designed to protect an electric circuits from damage caused by short circuit or overload.The basic circuit breaker working principle is that it is an automatically operated electric switch.It detects the fault condition and interrupt the continuity to stop the flow of electricity immediately.It is not like a fuse which operates once and need to be replaced,a circuit breaker can be reset (either manually or automatically) to resume it’s normal operation. There are variable sizes and varieties of circuit breakers are available according to the use.It is used for the protection of small household appliances up to the large distribution systems(Power Stations).

A Simple Circuit Breaker Have Following Components :

  • Electromagnet / bimetallic strip
  • Moving Contact
  • Switch
  • Stationary Contact
  • Upper and lower terminal
  • Catch


Working Principle Of Circuit Breakers :

As you can see it’s name is suggesting,whenever the current level goes up the circuit breaker breaks the connection between appliances and the main voltage source. Basically the circuit breaker consist of a simple switch connected to either an electromagnet or a bimetallic strip.When the current reaches onwards to the unsafe levels then the electricity magnetizes the electromagnet and the electromagnet is strong enough to pull down a metal lever connected to the switch linkage.Due to this operation the entire linkage shifts,tilting the moving contact away from the stationary contact to break the circuit and the electricity shuts off.The circuit breaker must detect a fault condition, in low-voltage circuit breakers this is usually done within the breaker enclosure.Circuit breakers for large currents or high voltages are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism.

The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting (opening) the circuit. Contacts are made of copper or copper alloys, silver alloys, and other highly conductive materials. Service life of the contacts is limited by the erosion of contact material due to arcing while interrupting the current. Miniature and molded case circuit breakers are usually discarded when the contacts have worn, but power circuit breakers and high-voltage circuit breakers have replaceable contacts.




  1. #1 by Sayandeep Dasgupta on October 16, 2011 - 5:02 pm

    Thank you for providing such a compact and precise presentation.

    • #2 by admin on October 17, 2011 - 8:31 am

      Hey Sayandeep !
      Thank you for stopping by and thank you for your kind words.I am glad to know that you have found this presentation useful.I hope to see you again here.

      Good Luck and God Bless!!

      With Regards!
      Samuel Joshua

  2. #3 by Avishek Palit on March 15, 2012 - 8:05 am

    Concise and Very Helpful
    Cleared my concept very nycly

    Cheers Samuel :)

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