Initiation Process of Vacuum Breakdown Between Cu and CuCr Electrodes

During the breakdown process in a vacuum, plasma flares initiated on cathode and anode surfaces expand and collide. The plasma flare behavior is quite important for the optimization of the spark conditioning of vacuum interrupters. Here, copper–chromium alloys are widely used as an electrode material in the large-capacity vacuum circuit breakers. In this article, high-speed spectroscopy is conducted on the plasma flares generated between a CuCr (Cr-35wt%) anode and a Cu cathode in order to elucidate the plasma temperature, particle composition, and electron density. The experimental results show that the anode flare has 1024–1025m−3 electron, and its temperature is approximately 13 000 K. The composition ratio of vapor atoms consisting the anode flare is Cu:Cr = 6:4–7:3, which is almost the same with that of anode material composition.