Analytical Calculation of the Electromagnetic Torque in Synchronous Machines Considering Slotting, Saliency and Saturation Effects

An analytical method for the evaluation of the electromagnetic torque in salient-pole three-phase synchronous machines is presented, capable to accurately take into account actual winding structure and stator and rotor air-gap geometry (slotting and saliency), under any saturated operating condition. The method is based on a Park d-q decomposition of the stator m.m.f. instantaneous distribution (preserving the spatial harmonics) and on the use of FEM identified saturation functions. A relevant feature is that the torque is expressed by means of the unsaturated self and mutual inductances, suitably corrected by using the saturation functions. Several transient FEM simulations validate the method.