Investigation on phase shift between multiple-winding sets in multiphase flux-switching permanent magnet machines

In this paper, winding configurations of multiphase flux-switching permanent magnet (FSPM) machines with multiple winding sets are investigated by finite-element analysis (FEA). The results reveal that for certain stator- and rotor-pole combinations, symmetrical winding configuration used in traditional machines may not invariably apply to multiphase machines in some respects, since the coils with opposite even-order harmonic vectors can not be utilized to reach symmetrical phase electro-motive-force (EMF). Besides, the phase shift between the adjacent two winding sets has significant influence on the electromagnetic performances, such as static torque and winding inductances, which are specifically analyzed basing on a dual three-phase 24-stator-slot/22-rotor-pole (24/22) FSPM machine. It shows that lower torque ripple and smaller self-inductance can be obtained with the phase shift of π/6. However, better fault-tolerance is achieved by symmetrical winding connection, due to the negligible magnetic coupling between phases.