Abstract:

Low short-circuit breaking capacity plays essential role for the residual current operated circuit breaker (RCB) sample testing in JP cabinet,which is required that the first pass yield (FPY) should be 100%.It is necessary to ensure the reliability of the low breaking capacity.By comparing with a few types of static contacts,U-shape static coutact of bottom incoming line is defined to be suitable for low breaking capacity,which can increase the electromagnetic repulsion force and shorten the breaking time.Gas blowing can accelerate the transfer of the arc,increase the arc voltage,and prevent the back breakdown.The contact pressure is adjusted to avoid critical breaking.The critical point of the small frame is limited outside the sampling inspection range,and the large frame is completely broken by the instantaneous tripping operating mechanism.The shorter the instantaneous tripping time is,the faster the breaking speed is. Through the comparative test of short-circuit breaking,the U-shaped static contact,gas blowing, contact pressure and instantaneous tripping time can improve the stability of low breaking capacity.

Key words: residual current operated circuit breaker, short-circuit breaking, arc voltage, back breakdown