Shock waves in arc chambers of miniature circuit breakers

The arc quench chamber is the essential component of a miniature circuit breaker. (MCB). The generation of pressure waves in compact arc chambers is discussed. Shock waves are generated during the whole arcing time. They are caused by rapid arc motion between the arc runners and by arc ignitions. Based on shock wave theory and experimental investigations, it is shown that rapid arc motion in small arc chambers causes shock waves which can affect the arc motion. This effect strongly influences the attainable current limitations and the peak let-through current. It is possible to improve the switching performance of a given arc chamber if the effect of the pressure waves is reduced by means of a suitable design, for example with vents or slots in the side walls