Magnetohydrodynamics simulation of arc motion in time-varying copper vapor–air mixture within medium-voltage DC air circuit breakers

Modeling arc–solid interaction precisely in medium-voltage DC air circuit breakers is challenging due to the complex processes of electrode erosion and metal vaporization during arc discharge. This study develops a DC air arc model based on magnetohydrodynamics (MHD) theory, which incorporates the time-varying copper vapor–air mixture along the arc's motion, rather than a fixed ratio of copper vapor. The model integrates a database containing the gas properties of copper vapor–air mixture, arc current, and the copper vapor mole fraction derived from pure air arc simulation. In the MHD model considering electrode erosion, the physical properties of the copper vapor–air mixture are updated at each time step based on the copper vapor mole fraction and the arc current. The simulation results of arc current and arc voltage during the breaking process are consistent with the experimental results. Additionally, the effects of different types and numbers of splitter plates, as well as short-circuit current on arc motion, are investigated. The arc duration time with laminated hybrid splitter plates is the shortest compared to fully ferromagnetic, fully insulated, and connected hybrid splitter plates. When the number of splitter plates increases from 7 to 67, the arc duration time is significantly reduced until saturation. Furthermore, as the short-circuit current decreases from 120 to 20 kA, the copper electrode erosion decreases substantially and finally stabilizes. This study presents an improved MHD model for arc motion in a time-varying copper vapor–air mixture, which is useful for the optimization of medium-voltage DC air circuit breakers.