Insulation characteristics and welding behavior of vacuum switch contacts made from various CuCr alloys

CuCr is generally accepted and applied as contact material in vacuum switches. Although CuCr has many well-known advantages it has, compared to CuBi, the disadvantage of welding more easily at high current-closing operations of circuit breakers. Thus, a currentless separation of the welds occurring after closing operations affects the dielectric properties of the open contact gap. In this study welding forces as well as field enhancement factors β and breakdown voltages of the contacts after currentless opening are investigated and used as diagnostic tools in order to study the influence of different CuCr compositions and manufacturing processes on the performance of butt-type contacts installed in a model vacuum breaker chamber