Modelling Nonlinear Magnetic Materials for Field Computation

Abstract

Most electromagnetic field computation programs are generally able to take into account the characteristics of magnetic materials of two kinds: (1) materials with linear characteristics which may be isotropic and possibly with residual magnetization. (2) soft isotropic nonlinear materials. The implementation of these models in a finite element package allows us to compute the magnetic field in a large number of electric devices. However, many devices are in reality made of materials with more complex characteristics. Especially those exhibiting anisotropic nonlinear phenomena, as in grain-oriented laminations, cannot be analyzed using presently available models. This paper presents two models of this kind of material in the frame of a magnetostatic analysis. They can be used for the computation of magnetic fields in configurations involving nonlinear permanent magnets and grain-oriented laminations. Furthermore we present a survey of the finite element formulations for this kind of problem with special attention to the methodology of implementation. Finally, some examples of the applications of the models are presented. These examples verify the proposed models by replicating on the computer the results of a practical experiment and demonstrate our new ability to model and predict complex magnetic phenomena.