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Friday, 3 April 2020

What is Vaccum Circuit Breaker? Working, Construction, Advantages, Application

Vaccum Circuit Breaker (VCB) arc quenching takes place in vaccum medium. 

All operations of switching that is on and closing of current carrying contacts are take place in vaccum chamber present in the circuit breaker so it is called vaccum circuit breaker.

Vaccum offers the highest insulation strength it has for superior arc quenching properties than the other medium. 

Vaccum Circuit Breaker
Vaccum Circuit Breaker


Construction of Vaccum Circuit Breaker

Construction of the vaccum circuit breaker is simple than the other circuit breakers. 

There are main three components are arranged in VCB i.e. fixed contact, moving contacts, and arc shield. This all components are fixed inside the arc interrupting chamber. 

The fixed and moving contacts of the breaker are placed inside the arc shield. The moving contacts of circuit breaker are move through a distance of 5 to 10 mm but it depends upon the operating voltage. 

Cross arm section of Vaccum Circuit interruption
Cross arm section of Vaccum Circuit interruption


From the stainless steel the metallic bellows are formed and this metallic bellows used to move the moving contacts. 

The ability of VCB is depends on the life of the all components are made and their arrangement it requires the repeated operations satisfactorily. 


Working Of Vaccum Circuit Breaker

When the contacts of the breaker  are opened in vaccum, an arc is produced between the contacts by the ionisation of metal vapours. 

However, the arc is quickly extinguished because of the metallic vapours, electrons and ions produced during arc rapidly condense on the surface of the CB constants resulting in quick recovery of dielectric strength. 

Cross arm section of Vaccum Circuit interruption Electrons and ions produced during arc are diffused in a short time and seized by the surface of moving and fixed members and shields. 

Arc get quickly extinguished due to the fast rate of recovery of dielectric strength in vaccum. 

Advantages Of Vaccum Circuit Breaker

Vaccum Circuit breaker has excellent recovery. 

For only half cycle less arcing occurs after the proper contact separation. 

It does not requires the aditional filling of Air or oil in it.

Breaker unit is compact and self contained.

Requires less maintanence.


Disadvantages of Vaccum Circuit Breaker

Loss of vaccum occurs because of transit damage 

It requires surge suppressors for the interruption of low magnetizing current in a certain range.

Applications of Vaccum Circuit Breaker

Industrial application where the high speed making switches requires because of VCB has excellent recovery.

It is also usefull for system which requires voltage from 11 to 33 KV.


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