Determination and Optimization of Multiphase Fractional-Slot Windings used in Permanent Magnet Synchronous Machines

The magnetomotive force spectrum of permanent magnet synchronous machines equipped with fractional-slot windings suffer in general from high values of sub and higher order spatial harmonic content. This paper deals with the development of a computer-aided heuristic algorithm for synthesizing and evaluating multiphase, multilayer, AC windings. Multiphase windings provide a higher degree of freedom with respect to harmonic current injection to increase the average torque density and this aspect is assessed for the case of fractional-slot windings. Eventually, four machines with different winding designs are compared for a full-electric car application in terms of performance indices such as torque, copper losses, and eddy-current losses.