This work presents an efficient iterative FEM-BEM procedure for the computation of the magnetic field in electric machines. The magnetic field is determined separately, by FEM, for a stator and rotor pole pitch, under the assumption that the vector potential satisfies Dirichlet and periodic boundary conditions. The normal derivative of the potential is obtained, which is then introduced into the integral equation written for the air region boundaries, thus yielding the new value of the potential. The numerical expression of the integral equation takes into account the periodicity of the geometrical structure and defines the relationship between the normal derivative and potential only for a polar pitch. The convergence of the procedure is ensured by the large value of the ferromagnetic permeability. For nonlinear media, the large value of the permeability is maintained by applying the polarization fixed point method.

Keywords: Magnetic field in electric machines, Periodic structures, Iterative FEM-BEM technique, Nonlinear media