Simulation of Heat Transfer and Fluid Flow in an Anode Melting Pool under High-current Vacuum Arcs

Anode activity is critical in a high-current interruption process of a vacuum interrupter. Under a high-current arc anode surface temperature may exceed melting point, thus an anode melting pool can form. Under such condition, an evaporation of metal vapor from an anode melting pool may play a role for a failure of the current interruption. The objective of this paper is to propose a model of fluid flow and heat transfer in an anode melting pool in a vacuum interrupter's high-current interruption process. The model incorporates heat transfer from arc plasma to anode surface, latent heat of solid/liquid phase and thermal physical properties of anode materials. The model uses heat flux and pressure distribution obtained from magnetohydrodynamic simulations as an input, which is a flow from high-current vacuum arc to the anode melting pool. By applying a finite volume method, the model analyzes temperature distribution of the melting pool and the erosion of anode surface after arcing. The temperature distribution and shape of molten region are given. The anode surface deformation caused by arcing is also shown in the model. A pit with 5 mm diameter and 1 mm in depth can be observed. The results can explain the liquid metal flow and the formation of a solidified shape of anode surface under arc pressure and heat flux input.