The Effect of contact material composition of AgWC and Axial Magnetic Field intensity on interrupting capability and chopping current

Silver tungsten-carbide (AgWC) has been used for contact materials of low surge type vacuum interrupter because of their properties such as low chopping current and low erosion. However the interrupting capability of AgWC is relatively less than CuCr. Generally, in order to increase the interrupting capability, Axial Magnetic Field (AMF) is applied for large rated currents. On the other hand, it is known that the contact materials greatly affect the interrupting capability and chopping current. In this paper, in order to increase the interrupting capability of low surge type vacuum interrupters, the effect of the intensity of AMF and composition of AgWC under AMF on the interrupting capability were investigated. The contents of Ag and WC were varied and Cobalt (Co) was added as a third element. Also the chopping currents were investigated. As a result, it was found that an increase of Co and a decrease of Ag content tended to increase the interrupting capability.