Modeling of electrical arc erosion for optimal choice of contact materials

The problem of an optical choice of contact materials for a given current range is very important now, especially for modern high-current electrical apparatus. The mathematical model of electrical are erosion of contacts made of multicomponent contact material is presented. It describes dynamical phenomena of phase transformations including both melting and evaporation from anode and cathode in dependence of the range of electrical current, arc duration and properties of contact material. This model is based on the Stefan problem with two free boundaries. A new method for the solution of this problem is presented. The results of calculations enable to explain experimental data for erosion of electrodes AgNi, AgCdO, AgSnO/sub 2/, AgNbSe/sub 2/. Factors influencing on the rate of arc erosion are found, and optimal proportions of components for contact materials providing minimum of arc erosion are discussed. (author)