Modelling of arc duration and erosion in electrical contacts of circuit breakers

The dynamics of the electrical and temperature fields in opening electrical contacts of circuit breakers is described by a non-linear transient mathematical model. It takes into account the interaction of the electrical arc with the contact surface, heat transfer with the melting and evaporation of the contact material, and the non-linear dependence of the arc electrical and thermal conductivity. The dependence of arc duration and conditions of arc instability are found as functions of the circuit parameters and the properties of the contact material. A new criterion of arc electrical conductivity is introduced to describe arc evolution. Calculation results of are compared with experimental data for AgCdO contacts. It is shown that the duration of the anode arc phase and the erosion rate depend on the redistribution of heat flux components entering the electrodes during arc evolution. Dependence of arc duration on circuit inductance for various currents is investigated.