Influence of Different Contact Materials on the Postarc Sheath Development in Vacuum Circuit Breakers

The vacuum arc characteristics and the subsequent dielectric recovery process significantly depend on the properties of the contact materials used in vacuum circuit breakers(VCBs). This paper employs a Particle-In-Cell Monte Carlo Collision (PIC-MCC) model to theoretically investigate the effect of contact material composition on the decay time of electrons, which serves as an indicator of the time required for the sheath to expand from the post-arc cathode to the anode, finally occupying the entire gap. The materials assessed include pure metals (copper(Cu), chromium(Cr), and tellurium(Te)) and copperchromium (CuCr) alloys with varying chromium concentrations, as well as CuCr30 alloy doped with minute amounts of element Te at different ratios (100 ppm, 1000 ppm, and 3000 ppm). The results indicate that for pure metals, the electron decay time is inversely proportional to the atomic mass of the metal, with chromium exhibiting the shortest decay time due to its lowest mass compared to copper and tellurium. In the case of CuCr alloys, it reveals that a higher chromium content correlates with slightly shorter electron decay times. However, the introduction of Te into the CuCr30 alloy, at varying concentrations, appears to have a negligible effect on the electron decay time, suggesting that the Te doping ratio is too minor to affect the post-arc sheath expansion process under the simulation conditions. These insights provide more in-depth knowledge of the selection and optimization of contact materials in VCBs.