Air Circuit Breakers - an Overview

Air Circuit Breakers are Circuit breakers where air is used as the medium of extinguishing the arc.  The air is usually compressed and kept in a cylinder.  When the breaker operates and the contact separation occurs,
the arc is driven into special arc chutes by means of compressed air which is blown through specially designed nozzles.  

Air Circuit Breakers are mostly used in the LV range.  They can interrupt currents of several thousand amperes.  

Air Circuit breakers are provided with an inherent current sensing mechanism like the thermo-magnetic release.

Arc Chute used in Air Circuit Breakers
The Arc chute is a component which is used to weaken and quench the arc.  The Arc Chute contains a number of splitters which split the arc into a number of sections.  This increases the length of the arc and quenches it.  The arc which is formed during the separation of the fixed and the moving contact is driven into the chute by means of the pressurized air.  The arc chute is usually made of composite refractory materials.  

Air Circuit Breakers are available in both Three pole and Four pole versions.

Air Circuit breakers are used widely in the industry for the protection of facilities and transmission lines.  They are also used for protection of electric equipment such as transformers, motors, etc.   Air circuit breakers are also used in mines and on board ships.