An integral equation approach to the computation of nonlinear fields in electrical machines

A numerical method based on an integral equation formulation, for the computation of nonlinear magnetostatic field, in two dimensions in cylindrical polar coordinates is given. The correctness of the method is illustrated by solving two linear two-dimensional magnetic field problems which have readily available analytical solutions. The dependence of the accuracy of the solution on the number and distribution of the meshes is studied on these examples. The method is then applied to the computation of the nonlinear field of a small salient pole synchronous machine. The technique used to accelerate the solution and other aspects of the solution are discussed. The program is used for the computation of magnetization characteristics, zero-power-factor characteristics, terminal voltages and their harmonics, and the field distribution in the air gap. Computed characteristics are compared with measurements. The results obtained illustrate that accurate and reasonably quick results are obtainable using this method