Electromagnetic Performance Analysis and Optimization of Novel Outer-Rotor Flux-Switching PM Machines

In order to enhance the torque performance and suppress the radial electromagnetic force, two types of outer-rotor flux-switching permanent magnet (OR-FSPM) machine topologies with stator magnetic bridge are proposed, that is, the odd side and even side PMs are arranged in the stator yoke, respectively. The arranged PMs are all radially magnetized and separated from the conventional PMs by an air gap for magnetic isolation. Firstly, the analytical formula of the radial electromagnetic force of the OR-FSPM machine is analyzed and deduced in detail based on the permeance-magnetomotive force model, which shows that the air gap electromagnetic force of the low-order spatial harmonics in the OR-FSPM machine will cause serious vibration and noise. Then, a parametric model is established, and a multi-objective optimization is used to optimize the torque performance and radial electromagnetic force harmonic of the dominant vibration. Finally, a comparison of electromagnetic performance between the proposed models and the conventional model has been carried out using finite element analysis. The results demonstrate that, without increasing the usage of PMs, the even-side model exhibits outstanding performance in improving output torque and reducing amplitude of dominant radial electromagnetic force harmonics. On the other hand, the odd-sided model achieves the lowest torque ripple.