Welding behavior of vacuum interrupters equipped with CuCr contact material caused by making and breaking operations under short circuit current interruption

Vacuum interrupter (VI) especially with high short-circuit interruption ability are mostly equipped with copper-chromium contact material. Especially for short circuit current making and breaking operations the contact material is based on CuCr-25...50 wt.-% in most of the cases by applying transverse magnetic field (TMF) or axial magnetic field (AMF) contact systems worldwide and multipurpose application. The study is carried out on standard VIs as well as optimized micro added elements and chemical compounds contact material equipped with TMF contact system. The contact material is based on the well-known solid state sintered material production technology. A large number of making operations under short circuit current conditions are done to investigate the welding forces. The welding forces especially after the making operation were measured by tensile test under dynamic condition. The statistic effect how the welding force develops is also being presented. Characteristics of the fractured surfaces and at the cross section were investigated by using light microscope, scanning electron microscopy (SEM) and the energy dispersive X-ray (EDX).