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

Abstract

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