Design Optimization of a Spoke-Type Permanent-Magnet Vernier Machine for Torque Density and Power Factor Improvement

Permanent-magnet vernier machine has an excellent potential for electric vehicles due to its desirable features of a simple mechanical structure and high torque density, whereas the poor power factor is its main drawback. In this paper, a spoke-type permanent-magnet vernier machine is designed and optimized for torque density and power factor improvement. First, the machine structure, operation principle, and sizing equation are introduced. Then, the machine is optimized by a multi-objective genetic algorithm. To enhance the optimization efficiency and accuracy, multi-level, sensitivity analysis, and approximate model technologies are employed in the optimization. It is shown that the improved torque density and power factor are achieved in the optimized machine as compared to the initial one. Finally, a prototype machine is built, and the experiments on the prototype machine are carried out to verify the design optimization.