What is circuit breaker? & Circuit breakers types & working

Circuit breaker Definition (Switching device).

The circuit breaker is an electro-mechanical tripping switch device and it is an on-load switching device. A circuit breaker is a protective equipment that can operate manually or automatically for making \ breaking circuits under normal or up-normal conditions such as short circuits, Overvoltage at the circuit, or feeder.

By Ironass - சொந்த முயற்சி, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7526849

How does a circuit breaker work?

Working of circuit breaker 

Whenever the fault occurs, in a circuit or feeder a protective relay senses the fault and closes the relay contact. This closed contact, energize the trip coil of the circuit breaker. Now, the trip coil initiates the operation of the spring mechanism where the stored mechanical energy at the spring is released and movable contacts of the circuit breaker open the circuit or feeder from the fault.

While movable contacts of the circuit breaker, breaks the circuit at that moment arching will produce on the contacts due to the flow of electric current. To protect the equipment and contacts from arching, an insulation medium is provided. Insulating medium clears the arc produced by current. This operation is called "ARC-EXTINCTION".

Types of circuit breaker based on the insulating medium,

1. Air circuit breaker(MCB).
2. Oil circuit breaker (tank type or bulk oil).
3. Minimum Oil circuit breaker (MOCB).
4. Airblast circuit breaker (ABCB).
5. Sulfur Hexa-Flouride circuit breaker (sf6 CB).
6. Vacuum circuit breaker (VCB).

Air Circuit breakers&Air blast Circuit breaker

• The air circuit breaker uses atmospheric air at constant pressure for arch extinction. Air acts as an insulating medium.
• Airblast circuit breaker(ABCB) uses highly compressed air for arc extinction, the pressure of air is very high for quench the arch. 

Oil Circuit breakers(BOCB & MOCB)

•  Oil circuit breaker uses dielectric oil as an insulating medium for arc extinction.
• In bulk-oil-circuit breakers, the contacts are getting open inside an enclosure of a steel tank filled with oil
• In minimum-oil-circuit breakers, the contacts are getting open in an insulating housing. It is filled with a dielectric oil medium.

Sf6 circuit breaker.

• SF6 circuit breaker uses sulfur hexafluoride gas for arc extinction, According to the construction of SF6 circuit breaker it is divided into two

1. Single pressure puffer type. 
2. Double pressure puffer type. 

Single Pressure Puffer Type.

In this type of circuit breaker, the single-piston is connected to enhance the pressure of Sf6 gas flow. The entire circuit breaker is filled with SF6 gas.

Double Pressure Puffer Type.

During the arc quenching process, sf6 gas from a high-pressure system is released into a low-pressure system over the arc to extinguish the arching. So this is called the Double-pressure puffer type.

Vacuum Circuit Breaker.

The contacts of the vacuum circuit breaker(movable and fixed contacts) are permanently enclosed on a sealed sputter shield of the circuit breaker. The sputter shield is filled with a vacuum. When arching time, the vacuum interrupts the arc and clears the arching.    

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