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Thursday, 2 April 2020

Air Circuit Breaker- Working Principle, Construction, Types, Advantages, Applications

It is an automatically operated electrical switch which protects the system or device from any fault overload or short circuit. It protects to the Electrical equipments.

If fault is detected by the circuit breaker it interrupts the flow of current and protects to the system and for the interruption it uses air that's why it is called Air Circuit Breaker.

Air Circuit breaker used compressed air to blow out the arc. It operates in air at atmospheric pressure. 

Air Circuit Breaker
Air Circuit Breaker

Working Principle of Air Circuit Breaker

Working principle of this circuit breaker is different from the other circuit brekers in some manner. For interrupting arc it creates an arc voltage in excess of the supply voltage.

When fault occurs in any part of the system the trip coils of the circuit breaker get energised and the moving contacts are pulled apart by some mechanism thus opening the circuit.

  When the contacts of circuit breaker are seperated under fault conditions, an arc is struck between them. The current is thus able to continue until the discharge ceases.

  The production of arc not only delays the current interruption process but it also generates enormous heat which may cause damage to the system or circuit breaker itself.

The circuit breaker increases the arc voltage by three ways
1. It may increases the arc voltage by cooling the arc plasma. If temperature of arc plasma decreases then the mobility of particle in arc plasma reduces. So that's why more voltage gradient is required to maintain the arc.

2. It may increases the arc voltage by lenghning the arc path.

3. Another one way is splitting up the arc into many series arcs also increases the arc voltage.

Construction of Air Circuit Breaker


Construction of Air- Blast circuit Breaker
Construction of Air- Blast circuit Breaker 


  The air circuit breaker consists of three types of contacts in a compressed air chamber.

1. The main contact-
This main contact carries the load current. They are made up of good conducting material, such as silver or copper.

It avoids over heating of the contacts while in service.

2. Arcing Contacts Of ACB-
It is made up of harder material which has high resistance such as tungsten.

When main contacts opens the arching current flows through the arching current with high resistance path.

3. Arching horns and chutes -
Arcing horns carries the arching current so they are made up of the high resistance and from harder material.

Chutes are made up of fire proof insulating materials because there are the last contact arc.

Cooling metal plates are connected to the chutes to convert the hot gasses and gives the way and cool the contacts arc the extinction of arc.

These all components are filled in circuit breaker chamber with compressed air which acts as dielectric material.


Types of Air Circuit Breaker

There are main four types of ACB.

1. Plain Break type air circuit breaker or cross blast air circuit breaker.

2. Magnetic blowout type air circuit breaker.

3. Air chute air break circuit breaker..

4. Air blast circuit breaker.(ABCB)


Advantages

• This is cheap and free available of the interruption medium.

• ABCB are chemically stable.

• Gives high speed operation.

•  It requires less maintenance.


Disadvantages


• Current chopping problem occurs.

• Produces high noise.

• Problem of restraining voltage.

• Compressor plant requires some maintanence.


Applications

• Used for protection of plants.

• Protection of electrical machines.

• For the protection of transformer, capacitor, generator.

• For low and high voltage and current applications.



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