Pareto Fronts in the Optimization of Fractional Slot Concentrated Windings for Rotor Loss Reduction in Surface Permanent Magnet Machines

Fractional-Slot Concentrated Windings (FSCWs) are an attractive option for the stator winding of synchronous permanent-magnet machines. However, they suffer from the drawback of large armature magneto-motive force (MMF) harmonics and consequent rotor losses. The use of a multi-layer design is a well-known method to synthetize FSCWs in which rotor losses are reduced compared to the usual dual-layer layout at the expense of a decreased MMF amplitude. This paper explores the effectiveness of the multi-layer FSCW design optimization for a variety of slot-pole combinations of practical interest. The optimization potential is presented in terms of Pareto fronts featuring rotor loss reduction versus MMF fundamental. Such potential is shown to strongly vary from one case to another, fading away for some well-defined slot-pole combinations.