Investigation on Effects of Low-Content W Additives on Post-Arc Process of Cr-Based Contact in Vacuum Circuit Breakers: MD Simulation

Low-content W addition in conventional Cu-Cr contacts for vacuum circuit breakers has the potential to enhance breakdown strength and hardness. However, high W content in contacts can induce interruption failure in the post-arc period due to strong thermal electron emissions from the W surface, raising the question of whether the low-content W addition might also lead to arc reignition. To investigate the influence of the low-content W addition on the post-arc recovery of vacuum gap, this work combined MD simulation and theoretical calculation methods to examine the arcing and postarc behaviours on localised Cr phases with W additions. The thermal electron emission was calculated by analysing the evolution of surface temperature and the structural change of the substrate during the arcing and post-arc stages. Simulation results indicated that low concentrations of W in small particle form do not adversely affect post-arc recovery, suggesting that small addition of W into C u-C r contact materials could potentially improve vacuum circuit breaker performance without the risk of thermal emission-induced failure.