ANALYSIS OF CONVERGENCE IN NONLINEAR MAGNETOSTATIC FINITE-ELEMENTS PROBLEMS

This paper deals with convergence difficulties using Newton-Raphson method in non linear magnetostatic problems. It is shown that the use of magnetostatic scalar potential can lead to a very unstable iterative process because of the shape of the residual function which is to be cancelled. Such effects do not exist when the vector potential is used and Newton-Raphson method is much more efficient. A simple example points out the behavior of Newton-Raphson method for both formulations. A method for reducing the CPU time required for determining the relaxation factor used to insure convergence in the case of scalar potential is also presented.