Non–Dominated Sorting Genetic Algorithm Based Investigation of Optimal Odd Slot Numbers for Stator Shifted Fractional–Slot Wound PMSMs

Stator slot shifting is widely implemented in fractional-slot wound permanent magnet synchronous machines for reduction of high spatial harmonic contents resulting in improved efficiency and flux-weakening performance. Existing method involves using twice the number of stator slots present thereby resulting in a winding topology with a coil pitch of 2. However, in this process, many slot-pole combinations, especially with odd slot numbers are neglected. Therefore, this paper proposes a procedure for stator slot shifting for n-phase fractional-slot wound machines considering all feasible slot-pole combinations. The slot-plot combinations are analyzed for performance attributes including winding factor, total harmonic distortion, minimum cogging torque and maximum torque per unit winding losses. Further, a non-dominated sorting genetic algorithm is used for optimal slot-pole selection for each phase number. The resultant machine performance characteristics of a sample best design candidate is verified using experimental data and finite element analysis.