Transient MHD Modeling and Simulation of High-Current Vacuum Arc Under Three Kinds of Interruption Processes

With the increase of interruption frequency of high-current vacuum arc (HCVA), the relaxation time of arc plasma is close to characteristic time of arc current and transient characteristics of vacuum arc plasma become more obvious. In this paper, based on a 2-D transient magneto-hydrodynamic model, HCVA under different interruption processes is simulated and analyzed. The simulation results of power-frequency (50 Hz) current show that transient simulation results are the same as those of the steady-state model, as characteristic time of current is much longer than relaxation time of plasma. For fast current drop stage in dc interruption process, simulation results show that higher frequency makes current drops faster and ion number density larger; besides, residual plasma density between electrodes at current-zero moment is higher, and interruption becomes more difficult. Finally, transient characteristics of high-frequency HCVA is also simulated and analyzed. Simulation results show that change curve of ion number density lagged behind current curve; higher ion number density in the second 1/4 cycle can lead to reignition more easily.