Investigation of Unipolar End Flux Leakage in Dual-PM Consequent-Pole Vernier Machines

The unipolar end flux leakage of dual-permanent magnet (PM) consequent-pole (CP) Vernier machines is investigated in this article. The relationship between the stator and rotor pole number combinations and the significance of unipolar end flux leakages generated by stator PMs and rotor PMs is revealed for the first time. It is found that the unipolar end flux leakage is affected by the stator/rotor pole number combinations. The lower the pole numbers of armature and rotor, the higher the unipolar end flux leakage. Rotor PMs generate more unipolar end flux leakage when the rotor poles are fewer than the stator poles, and stator PMs generate more unipolar end flux leakage when the stator poles are fewer than the rotor poles. By comparing dual-PM CP Vernier machines with single-PM CP machines, it is found that dual-PM CP Vernier machines generate higher unipolar end flux leakage. The nonmagnetic shaft is used in dual-PM CP Vernier machines to decrease unipolar end flux leakages without affecting the performance. Two dual-PM CP Vernier machines with magnetic and nonmagnetic shafts are prototyped and measured to verify the analyses.