Numerical estimation of the electro-thermal conditions for vacuum switcher chamber operation

Plasma phenomena have different and complex features depending on concrete physical conditions. The plasma control and characteristics during the switching processes are directly dependent on the ignition conditions of the electric arc. The thermal state of the electric contacts before the moment of disconnection has an important role. The paper presents a mathematical model and an iterative solving method for the combined electrothermal problems referred to a vacuum medium-voltage contactor. These are described by partial differential equations for non linear and non homogeneous domains. It is used a step by step computing procedure, applied successively, for solving separately, the non-linear coupled problems of electrical and thermal field. The discrete mathematical model is based on the Finite Element Method. In order to insure the numerical convergence and the minimization of the discretization error, successive refinement levels are used for the triangulation mesh, which are concentrated near the contact zone. Both the analytical and discrete models are defined for a two-dimensional domain, taking under consideration the cylindrical symmetry of the physical domain and of the boundary conditions. This enables the analysis of the solution for an axis-symmetrical section, based on the equipotential lines and on the radius-dependent thermal distribution.