Nonlinear convergence acceleration of magnetic field computation

Finite-element method (FEM) has been widely used to analyze the performance of electric devices. Due to the nonlinear permeability of iron materials, Newton-Raphson method is usually used in FEM for nonlinear iteration. To accelerate the nonlinear convergence, one effective technique is proposed. The method is to use different relaxation factors for materials in the electric device. The difference between this proposed method and conventional method is that in conventional method only one relaxation factor is used for all solutions. With the proposed method the total computing time of iteration process of FEM can be reduced effectively. The proposed algorithm is tested on a highly saturated transformer to showcase its effectiveness.