Elimination of Unipolar Leakage Flux in Consequent-Pole PM Machines by Employing Novel Pole Sequence

This paper proposes a novel consequent-pole permanent magnet (CPM) machine featuring N-iron-N-iron-N-S-iron-S-iron-S sequence to eliminate the unipolar leakage flux in the conventional CPM machine. Furthermore, the tangential magnetized PMs are embedded into the rotor of the proposed CPM machine to improve the unbalanced flux and, hence, enhance the output torque and efficiency. Both the rotors of the proposed and conventional CPM machines are optimized by the finite element (FE) analyses. It is demonstrated that the unipolar leakage flux does not exist in the proposed machines, and hence, the magnetization of the mechanical components can be effectively eliminated. In addition, the electromagnetic performance of the proposed CPM machine, including the phase back EMF, average torque, torque ripple, loss, efficiency, unbalanced magnetic force (UMF), and unipolar leakage flux, is compared with the conventional CPM machine. It shows that the proposed CPM machine can obtain similar torque and efficiency to the conventional CPM machine, while it reduces the UMF. Finally, a CPM machine is prototyped and measured to validate the analyses.