Mathematical minimization of the time harmonics of the EMF of a DC-PM machine using a finite element method

A procedure allowing the geometrical shape optimization of a permanent-magnet DC (DC-PM) generator in order to reduce the AC components of its open-circuit electromotive force (EMF) is proposed. A 2-D software based on a finite-element method (FEM) associated with a mathematical optimization technique makes it possible to establish an automatic optimization treatment of that generator. The tools, such as the rubber mesh, that make such a procedure possible are presented. The rubber mesh tool associated with an air gap element allows the finite-element topology to be kept constant in the course of one iteration of the optimization process. The formulation of the problem to be minimized has been carried out using a discrete Fourier transform so that the considered harmonics can be substantially reduced