Interaction between arc root redistribution, melt pool dynamics, and contact erosion in DC Switches

Electric arc discharges significantly limit the service life of electromechanical switching devices due to severe erosion of contact surfaces. While arc behavior has been extensively studied, the coupling between arc dynamics and the molten pool response on contacts remains insufficiently understood. In this work, we develop a time-dependent numerical model to simulate the erosion of a copper contact pair under DC arc discharge. The model couples arc magnetohydrodynamics (MHD) with the thermally and mechanically driven deformation of the molten pool using a level-set method. Key physical mechanisms, including phase change, recoil pressure, Marangoni convection, and surface tension, are incorporated to capture the complex interactions at the arc–molten pool interface.

To better represent arc–contact coupling, thermionic emission from the contact surface is included based on the Richardson equation to model the current density near the arc root. The simulation results reveal that the formation of a molten pool significantly alters the arc attachment, which in turn intensifies pool deformation and droplet spattering. Under the influence of arc-induced forces—particularly recoil pressure—the molten pool evolves into a crater with a concave center and raised edges. Numerical predictions of the eroded morphology are compared with 3D surface profilometry measurements, demonstrating good agreement and supporting the validity of the proposed approach.