Research on the High Efficiency External Rotor Permanent Magnet Motor Based on Halbach Array

The external rotor permanent magnet motor has large air gap area, which can get high output torque. In order to reduce the stator core loss and the magnet eddy-current loss caused by high harmonic wave in the air-gap flux, in this paper a new kind of Halbach array form has been presented to achieve more sinusoidal air gap flux wave. Firstly, the optimal Halbach array form of m=3 was obtained by analytic calculation and finite element analysis (FEA), which has optimal air-gap flux waveform. Then we have analyzed the influence of axial and radial segmentation of magnets on the eddy-current loss. Through the optimization analysis of stator slot, the total loss has been reduced. Finally, the correctness of the theory is verified by prototype experiments.