Cathode spot emergence on copper and chromium alloy used in vacuum breakers

Abstract

For copper and chromium, used in alloy component electrodes of vacuum circuit breakers, the cathode spots are initiated on micron meter spikes above the surface of the electrode, they are considered as cylinders with a height equivalent. After spraying of these peaks the cathode spot reaches the surface of the electrode on which it will expand according to a proposed model. The two studied materials have quite different thermophysical properties, but they lead to comparable results. In both cases the erosion of cylindrical spikes is due to the flow of energy provided by the cathode spot, the mechanism is different from those found for the molten bridge or for fuses where the Joule effect is the only factor to take into account.