Numerical Simulation on Copper Vapor Behavior in Vacuum Arcs during Low-Current and Current Decaying Process using Moving Particle Method

A vacuum arc discharge occurs between the electrodes during current interruption process in the vacuum circuit breaker (VCB). This vacuum arc is maintained by metal vapor supplied from the metal electrodes. The vacuum arc behavior is extremely complex and therefore difficult to elucidate solely from experimental observations. Therefore, it is essential to investigate the vacuum arc behavior from numerical simulation to improve the current interruption performance of VCBs. We have been developing a numerical model to simulate the behavior of low-current vacuum arc by our original model, a hybrid model of the Moving Particle Semi-implicit (MPS) method and the Finite Volume Method (FVM). In this paper, the low-current decaying vacuum arc was simulated from 50 A to 0 A at different current decay rates using our developing MPS+FVM model. As results, during the current decay process, the metal evaporation rate from the cathode spot decayed with time due to a decrease in Joule heat, leading to a decrease in the amount of metal vapor supplied to a space between the electrodes. The heavy-particle temperature $(T_{\mathrm{h}})$ near the cathode spot was found to remain high, whereas the averaged $T_{\mathrm{h}}$ between the electrodes decreased due to the smaller power injected between the electrodes.