The air blast circuit breaker needs an auxiliary compressed air system which supplies air
to the air receiver of the breaker. For opening operation, the air is admitted in the arc
extinction chamber. It pushes away the moving contacts against spring pressure. In doing
so, the contacts are separated and the air blast takes away the ionized gases along with it
and assists s arc extinction. After few cycles the arc is extinguished by the air blast and
the arc extinction chamber is filled with high pressure air (30kgf/cm
2
). The high pressure
air has higher dielectric strength than that of atmospheric pressure. Hence a small contact
gap of a few centimeters is enough.