Mixed FEM2D — Analytical method to evaluate E.M.F. and torque in surface PM Synchronous Machines

The paper presents a method to evaluate the e.m.f.s and torques waveforms in a surface PM Synchronous Machine. The key feature is the mix of FEM2D and analytical procedures, in order to exploit the positive features of FEM methods (easy applicability even in case of complex geometry), but maintaining some flexibility of the analytical approach. The method is based on the FEM identification of suited “field functions” which describe the air-gap flux density behavior. E.m.f.s and torques are then evaluated by analytical expressions, based on the calculation of suited inductances and their derivatives. The soundness of the method is proved by the comparison with transient 2D FEM simulations.