FEM2D based analytical model of the air gap magnetic field in surface PM synchronous machines

The paper presents an analytical model of the air gap field in a surface mounted PM Synchronous Machine. The method is FEM2D based, because it starts from the FEM identification of suited “field functions”: each field function describes the air gap flux density behavior, related to one field perturbation cause, acting alone (stator slotting, rotor anisotropy, field excitation source, armature reaction m.m.f.s). The soundness of the method is proved by the good agreement of the field behavior obtained by FEM and by the proposed methodology. The field analytical expressions are suited to be used to evaluate the waveforms of e.m.f.s and torques.