Investigation of relation between miniaturization of Cr and breakdown characteristics of CuCr electrode in vaccum

CuCr alloys are widely used in vacuum interrupters. For development of vacuum interrupters, we need to improve the breakdown characteristics of CuCr electrodes, which are influenced by the electrode surface condition. It has been found that both the electron beam and current conditioning treatment modify the CuCr electrode surface which improves the breakdown characteristics. However, the relation between Cr particle size in this melting layer and the breakdown voltage is not clear. Therefore, we measured the breakdown voltage and Cr particle size after several kinds of surface treatment in order to investigate the relation between Cr particle size in the treatment layer and the breakdown voltage. Results show that miniaturization of Cr particles tends to improve the breakdown characteristics of CuCr electrodes in a vacuum.