Depending upon the direction of air blast in relation to the arc;air blast circuit breakers are classified into: (i)Axial-blast type in which air-blast is directed along the arc path as shown in figure below. (ii) Cross-blast type in which air blast is directed at right angles to the arc path as shown in figure below (iii) Radial-blast type in which the air blast is directed radially as shown in figure below (i) Axial-blast air circuit breaker The figure below shows the essential components of a typical axial blast circuit breaker.The fixed and moving contacts are held in closed position by spring pressure under normal conditions.The air reservoir is connected to the arcing chamber through an air valve.This valve remains closed under normal conditions but opens automatically by read more

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These type of breakers employ ‘air blast’ as the quenching medium.The contacts are opened by air blast produced by the opening of blast valve.The air blast cools the arc and sweeps away the arcing products to the atmosphere.This rapidly increases the dielectric strength of the medium between contacts and prevents from re-establishing the arc.Consequently the arc is extinguished and the flow of current is interrupted. Advantages An air blast circuit breaker has the following advantages over an oil circuit breaker: The risk of fire is eliminated The arcing products are completely removed by the blast whereas the oil deteriorates with successive operations;the expense of regular oil is replacement is avoided The growth of dielectric strength is so rapid that final contact gap read more

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