Design and Analysis of Permanent Magnet Machines With Multiple Arc Pole Ratios in Stator Teeth

This paper is to propose a new design method of permanent magnet (PM) machines with multiple arc pole ratios in stator teeth (MAPR-PMMs), in which edges paralleled to airgap in stator teeth adopt different lengths to optimize airgap flux density for high torque quality. The advantages of the proposed MAPR-PMMs are easy to manufacture, simple design process and minor structure changes for electromagnetic performance improvement. The analytical modelings of MAPR-PMMs with single- and dual-stators for permeance calculation are provided. The relationship of the conventional PMM and field modulation machine with single-stator when employing fractional slot concentrated windings is analyzed by investigating the main working harmonic components because the only difference between them is arc pole ratio. Three representative MAPR-PMMs with different numbers of arc pole ratios are designed and discussed when compared to the conventional PM machines with only one arc pole ratio in stator teeth. The prototypes of MAPR-PMMs with 2 and 3 arc pole ratios are manufactured and tested for comparison and validation. The finite-element-analysis-predicted and experimental results confirm the validity of presented design method and the merits of MAPR-PMMs.