The theoretical prediction of current chopping ability of vacuum contact materials

Up to now, a theoretical model has not been established which shows the relationship between chopping current and material parameters and has direct significance for materials selection and manufacture. In this paper, based on the heat conduction equation and energy balance principle on the cathode surface, a new criterion, which can predict the current chopping ability and determine the chopping current sequence of different contact materials, is developed and verified by experiment. The new criterion clearly indicates: increasing the electrical resistivity, ionization potential, or decreasing the boiling point, specific heat, work function of material, atom weight, latent heat of fusion, latent heat of evaporation, will make the vacuum material´s chopping current low.