The Application of Magnet Structures to Reduce the Cogging Torque Associated with Fractional Slot Number in Permanent Magnet Generators

Abstract

This study proposes the application of a magnet structure to minimize the cogging torque (CT) and unstable pull in endless magnet generators. The investigation was conducted using an integral slot number of 24 slots and 10 poles, as well as a fractional slot number of 18 slots and 8 poles. The purpose of combining the multi-slot mechanism with pole arc optimization at the magnet edge was to underestimate the peak CT through a reduction in the quantity of tangential flux density. However, the results indicate that CT did not decrease significantly using this method, and this led to the optimization of the edge shape in the magnet structure through the introduction of the surface response method. The combination method’s goal was to ensure a significant reduction in both the integral and fractional slot numbers of the permanent magnet generator. The results show that the CT in the structure with an integral slot number of 24 slots and 10 poles decreased to around 99.4% compared with the baseline structure, while the CT in the structure with a fractional slot number of 18 slots and 8 poles was minimized to 98.8%. This led to the conclusion that the techniques could be combined in structure with any number of integral and fractional slots to reduce CT.