Optimal Design of an Outer-Stator Magnetically Geared Permanent Magnet Machine

In this paper, a magnetically geared permanent magnet (MGPM) machine is proposed for the use in wind power generation. The structure layout, operating principles, and equivalent circuit of the MGPM machine are first described. Then, an efficient finite-element-method-based design optimization approach is formulated and implemented in the design of the machine. The optimized machine shows that a rated torque density close to 70 kNm/m(3) can be achieved, which is significantly higher than that of the conventional electrical machines. Furthermore, a prototype machine based on the design is constructed and experimentally evaluated. The measured torque performance shows good agreement with the predicted one, but a significant difference exists between the measured and calculated efficiencies. This is mainly due to higher than the expected mechanical losses in the MGPM machine. Relevant conclusions are drawn based on the analysis of presented results and some key design-related aspects.