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 (N-R) method is usually used in FEM for nonlinear iteration. To accelerate the nonlinear convergence, one effective technique to accelerate the nonlinear convergence is proposed. The basic idea is to use different relaxation factors in different material regions in electric devices . The difference between this proposed method and conventional method is that in conventional method only one relaxation factor is used for all material regions. With the proposed method the total computing time of iteration process of FEM can be reduced effectively . The proposed algorithm is tested on a magnetic field problem of a highly saturated transformer to showcase its effectiveness.