MMF Harmonic Analysis of Multi-M-Phase Fractional-Slot PM Machines With Partial Operating Winding Sets

This article investigates the classification of magnetomotive force (MMF) harmonics in multi-m-phase fractional-slot machines when arbitrary m-phase channels are disconnected due to faults. By employing a universal Q-set m-phase winding arrangement, this study reveals the intrinsic relationships between MMF harmonics generated by different winding sets. Through analytical derivation, the results show that harmonics of the same order from different winding sets share the same amplitude but differ in phase shifts. For harmonics of different orders, certain symmetries and similarities are found in their phasor diagrams. Based on the discovered rules, all composite MMF harmonics can be classified into at least (Q/
$2+1$
) groups when Q is even and (
${Q} +1$
)/2 groups when Q is odd. The MMF harmonics within the same group vary synchronously as the faulty condition changes. The findings are validated by the finite-element (FE) simulations on machines with even and odd Q, respectively.