Doped Cu/Cr vacuum interrupter contact material enables increased short-circuit interruption performance

Abstract:
The predominant contact materials for vacuum interrupters are Cu/Cr composite materials consisting of typically 50 – 75 wt.% copper and 25 – 50 wt.% chromium. Powder metallurgy is used for the mass production of these materials. It is known from experience that the chemical composition of the specific contact material can influence the performance of vacuum interrupters. In the present work it was found empirically, that by addition of a small amount of Si to the Cu/Cr material, the short-circuit interruption performance can be increased substantially. A new process method was developed, which enables a homogeneous and precise Si doping of Cu/Cr at the ppm level. The paper discusses the microstructural features of this new material, their relationship with physical material properties, and the final vacuum interrupter performance in short-circuit interruption tests. A comparison between doped and conventional, un-doped Cu/Cr materials is made.