Comparison and Analysis of Dual Stator Permanent Magnet Vernier Machines with Different Pole/Slot Combinations for Low Speed Direct Drive Applications

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International Journal of Applied Electromagnetics and Mechanics

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Permanent magnet vernier machine (PMVM) based on flux modulation principle has attracted increasing attention in low-speed direct-drive applications due to its high torque capability. A dual-stator PMVM topology with sandwiched spoke-array PM rotor is presented to produce higher air-gap flux density and larger torque in this paper, and the space utilization and the energy conversion efficiency are improved significantly. Two representative dual-stator PMVMs (DS-PMVMs) are designed with this topology, the pole/slot combinations and gear ratios of which are 18 slots/30 poles and 18 slots/28 poles, 5 and 3.5, respectively. In order to reveal the advantages of the proposed topology and assess the torque characteristics of the proposed machines with different pole/slot combinations, the electromagnetic characteristics of these two machines are quantitatively compared and analyzed by using finite element method (FEM). The results demonstrate that the 18 slots/28 poles DS-PMVM can offer higher output torque, lower torque ripples, lower cogging torque and higher power factor owing to its optimal pole/slot combination. In addition, the unbalanced magnetic pulls (UMPs) of the two machines are also investigated, and the UMP of the 18 slots/30 poles DS-PMVM is smaller than that of its counterpart due to its symmetrical winding.



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