Analysis of Micro Arc Plasma Characteristics of the Mixed Metal Vapor in Vacuum Circuit Breaker

For the mechanical vacuum circuit breaker, the particle composition group of the metal vapor arc varies with different operating conditions, which will lead to the discontinuous variation of the electrical conductivity between electrodes. The change of mixed metal vapor arc macroscopic electrical characteristics results from the space-time change of microscopic arc plasma characteristics. For the vacuum circuit breaker, the interruption performance is directly influenced by the composition of the metal vapor arc plasma and the characteristic parameters. For evaluating the electrode characteristics and establishing a database of mixed metal vapor arc characteristic parameters for the vacuum interrupter, this paper presents a study of the copper chromium (CuCr) alloy contacts used in vacuum circuit breakers. The Eindhoven model was used to derive a Local Thermodynamic Equilibrium (LTE) vacuum arc plasma particle composition model. The thermodynamic parameter variation of metal vapor arc plasma is calculated by statistical thermodynamic method, and the electrical conductivity was calculated by Chapman-Enskog method. The mass density, enthalpy, specific heat and electrical conductivity for different alloy proportion (CuCr25, CuCr40, CuCr50, CuCr60 and CuCr75) were compared and quantitatively characterized.