Tuesday, 31 March 2020

Circuit Breaker- Working Principle, Construction, Types.

Circuit Breaker
Circuit Breaker
  • The electrical circuit is an switching device that interrupts the fault current or the abnormal current. Circuit breaker is a safety device used protection of electrical equipments. 
  • It can be operated manually and automatically. It protects an electrical circuit from damage caused by abnormal or excess current from an overload or short circuit.
  • In indoor applications of Circuit breaker we also use it as an isolator.

Construction of Circuit Breaker

There are many components in circuit breakers.

1. Frame
To all the circuit breaker components frame provides the insulation. Frame is constructed by thermal set plastic such as glass polymer.

2. Contacts
Contacts are the way through which the current flows in circuit breaker. When fault current flows and circuit breaker turns off then C.B. interrupts the flow of current by seperating it's contacts.

Contacts are of two types
1. Straight-Through Contacts
2. Blow-Apart Contacts

3.Operating Handle
Operating handle is connected to the movable contacts arm through an operating mechanism. Operating handle is moved from the OFF to the ON position.

4. Trip Unit
To providing the open and close its contacts manually circuit breaker must automatically open its contacts when fault current is sensed. It determines when the contacts will open automatically.

Construction of Circuit Breaker

Construction of Circuit Breaker

Working Principle of Circuit Breaker

  • A circuit breaker sense the electrical current flowing through it and breaks that current if current exceeds the limit that is abnormal current.
  • There are two common ways that circuit breaker sense the current Thermal and Magnetic
  • Small breakers are usually thermal and work by passing the current through a heating element and break the current if that element gets too hot.
  • In simple terms, it's a switch which turns itself off. Its just two metal contacts which can be moved apart, like any other switch and a solenoid which is an electromagnetic device which moves one of the contacts. 
  • The solenoid is calibrated so that at a certain electrical current it activates and turns the switch off. 
  • When a circuit has a breaker in it and the circuit tries to draw more current than it can handle it turns off and deactivates the whole circuit once the problem with the current is fixed, we can turn the switch back on, and the circuit is fine again. 

Types Of Circuit Breaker 

  • Circuit Breakers are mainly classified on the basis of rated voltage.
  • Circuit breaker below the rated voltage of 1000V are the Low Voltage Circuit Breakers and above the voltage 1000V are the High Voltage Circuit Breakers.
  • They are mainly classified on basis of the medium of arc extinction are following.

1. Oil Circuit Breaker 
2. Bulk Oil Circuit Breaker
3. Minimum Oil Circuit Breaker
4. Minimum Circuit Breaker
5. Air Blast circuit Breaker
6. Sulphur Hexafluoride Circuit Breaker
7. Vaccum Circuit Breaker
8. Air break Circuit Breaker


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