Heating of an electrical contact by a vacuum arc

The electric arc is a self-sustained electric discharge characterized by a very high current density at the cathode and a low cathode voltage. This corresponds to high power densities causing heating, melting and evaporation of the electrical contact. The erosion of an electrical contact implies a limitation of the lifetime of the electrodes in the electric interruption devices. The cathode and anode spot are defined as superheated regions of cathode and anode surfaces from which the metal vapor emerge. The Heat sources of a contact are the Joule heat produced by the current and the impinging positive ions on the surfaces. The hot surface emits electrons and metal vapor. In this paper, the heating process of an electrical contact with an electric arc in vacuum is considered. We present a numerical simulation of an electrical contact heated by an arc in vacuum for tungsten, copper and aluminum electrodes. The purpose is the identification of the main source of heating of the electrical contact in vacuum arc discharge. We also investigate the time needed for an electrode to reach the melting and vaporization temperature and compare these times to those experimentally obtained by some authors on arcs with duration less than 100 nanoseconds.