Design and Analysis of a High Torque Density Hybrid Permanent Magnet Excited Vernier Machine

Permanent magnet (PM) excited vernier machines capable of high torque density have good potential for electric vehicles while requiring high rare earth PM consumption. To achieve a high torque density at a reasonable material cost, hybrid PM excited vernier machines incorporating both expensive rare earth and low-cost ferrite magnets are investigated in this paper. Various combinations of PM arrangements for the hybrid permanent magnet excited vernier machine are investigated to acquire low cost and superior torque density. The best solution obtained is that the PM on the stator adopts rare earth material while the rotor uses ferrite. Furthermore, the PMs on the stator are arranged in an iron-cored Halbach array, which can reduce leakage flux and enhance flux density effectively and the ferrite PMs are used in the rotor, therefore, high-temperature demagnetization is avoided. Then, the reluctance torque and the cogging torque can offset each other effectively, which is beneficial to reducing the torque ripple and smoothing the electromagnetic torque. Finally, a prototype is manufactured and tested to verify the correctness of the theoretical analysis.

Automated summary

This paper investigates a hybrid permanent magnet excited vernier machine that can achieve high torque density and reduce material cost. By using rare earth magnets on the stator and ferrite magnets on the rotor, high-temperature demagnetization can be avoided. Furthermore, arranging the permanent magnets on the stator in an iron-cored Halbach array effectively reduces leakage flux and enhances flux density.