Numerical calculation of nonlinear transient field problems with the Newton-Raphson method

The modeling and numerical simulation of transient electromagnetic field problems with ferromagnetic materials is described in the context of the Finite Integration Technique (FIT). This paper presents a Newton-Raphson method adapted to FIT which is faster than the Successive Approximation technique. Due to the nonlinear material behavior these algorithms are not always stable. In order to improve convergence, a dynamic relaxation process and a suitable interpolation of the magnetization curve are presented. Results of these iterative schemes are compared with measurements of typical benchmark problems.