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.