Analysis and Reduction of Unipolar End Leakage Flux in Consequent-pole Vernier and Fractional Slot PM Machines

This paper investigates the unipolar end leakage flux in consequent pole vernier and fractional-slot permanent magnet machines. A composite rotor structure, consisting of a non-magnetic shaft and/or a non-magnetic ring inside the rotor core, is proposed to reduce the unipolar end leakage flux, without sacrificing the torque capability. Its effectiveness has been verified by three-dimensional finite element analyses.