The prediction of current distribution in an induction heating installation by a coupled finite-boundary-elements method (abstract)

Abstract

The finite elements method (F.I.M.) is a powerful means to resolve the diffusion equation and to predict the current distribution in the induction heating installations. However, it is confronted with two difficulties: the relative movements of different parts and definition of the infinity for the open boundary systems. The boundary element method (B.E.M.) can resolve these two problems but it is not applicable for the nonlinear systems.1 In this paper we propose a coupled finite-boundary-elements method to study a planar circular inductor parallel to a metallic load and fed by a voltage U with a variable frequency up to several kHz. We resolve the diffusion equation in the volume of the inductor and load by the F.E.M. and we use the B.E.M. to define the boundary conditions at their surfaces. The F.E.M. leads to a symmetrical band matrix but the coupled method changes it to a nonsymmetrical one and increases its width. To improve it, we use an iterative method that preserves the structure of the F.E.M. matrix. The calculations shows that the current is distributed nonuniformly around the coils. It is important near the load and very low near the neighboring coils. For the middle coils the current changes the direction in some areas. This nonuniform distribution of current increases the resistance of the inductor and can improve the generator design.