Numerical Simulation of Transient Vacuum Arc with Active Anode Modes

This work investigates the transient arc behavior during the anode spot mode with CuCr25 electrodes theoretically and experimentally. In the simulation, a 2D transient magneto-hydro-dynamic (MHD) model considering multi-component plasma is used to calculate the arc parameters. Then, the energy flux is obtained to calculate the anode temperature in next time step. Simulation results show that when the anode temperature is high enough, the anode vapor density increases significantly. Therefore, ions from the cathode are decelerated by the anode vapor when arriving at the ionization layer, leading to changes in the ion temperature. Then, the arc current is more likely to flow to the edge of the atom vapor area instead of the anode center. Thus, the energy flux to the anode begins to heat the area around the anode spot, leading to a more uniform anode temperature distribution and a larger anode spot. The maximum anode temperature occurs after the peak current due to the thermal inertia. Experiments using optical methods for anode temperature determination are also conducted to verify the simulation results.