Distribution factor Unified Calculation of Fractional-Slot Winding Permanent-Magnet Machine for MMF Harmonic Analysis

This paper proposes a unified calculation method for distribution factors of the permanent-magnet (PM) machine equipped with fractional-slot windings. It lays a theoretical foundation for analyzing magnet motive force (MMF) harmonics. Firstly, the slot-pole combination (SPC) characteristics and winding arrangement regulations of fractional-slot PM machines are investigated. Then, the concept of SPC normalized ordered number pairs (SPC-NONP) is innovatively proposed, unifying the calculation of the distribution factors. Subsequently, the expressions of harmonic distribution factors are derived from three aspects: N _coil is odd, N _coil and Q are even, and N _coil is even while Q is odd. The above studies form a general analysis theory of m-phase winding PM machine MMF harmonics. Besides, a 27-slot 8-pole internal PM machine is optimally designed to verify the theoretical analysis results and analyze its electromagnetic performance. Finally, the PM machine prototype is built, and experimental results are given for validation.