Contact Material for Vacuum Interrupters based on CuCr with a Specific High Short Circuit Interruption Ability

Vacuum interrupters (VI) with specific high short circuit interruption ability are mostly equipped with the well known contact material based on copper and chromium. A review of different production techniques as well as behaviour and microstructure of commercially available materials is presented with emphasis on two of the predominantly applied methods. The contact material´s switching performance strongly depends on it´s mechanical properties, gas and element concentration evaluated for each batch of base material. The contacts microstructure is investigated using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Switching performance is proven on standard Vis and the examination is held in a high performance lab by interrupting a sequence with a huge number of short circuit currents in accordance to the standards according IEC 62271-100. When conducting limitation tests at higher demands than required a ranking of material batches is presented. The study is based on standard contact material with a chromium content of 25 wt.% used on the transverse magnetic field (TMF) contact system. Derived from the results a very compact VI for a rating of 40.5 kV at 40 kA with increased specific performance is introduced