Investigation of current breaking capacity of vacuum interrupters with focus on contact material properties with the help of a reference model vacuum circuit breaker

This paper presents the performance of current breaking tests with a model vacuum circuit breaker and copper chromium disc-shaped contacts. The specifications of the model circuit breaker and the characteristics of the test circuit define a reference for the current breaking capability that serves as basis for further optimization. This reference breaking capability is defined with a standard powder-metallurgical contact material with 75 wt% copper and 25 wt% chromium. Information about the statistical reproducibility of the current interruption capability, the permissible number of high current switching events without contact wear, the recovery of breaking capability after current over-stress and the increase of breaking capability of virgin contacts due to high current conditioning could be gathered.