Investigation of Permanent Magnet Brushless Machines Having Unequal-Magnet Height Pole

Since the torque ripple reduction by adopting magnet-shaping methods is often associated with a negative impact on electromagnetic torque as well as increased cost, this paper proposes magnet poles having unequal magnet height, i.e., the Hat- and T-type magnets, together with optimized Halbach magnetization. An analytical model based on subdomain technique is employed for investigation, while its validity is examined by finite-element analysis. It shows that comparing to conventional three-segment Halbach array, Hat-type magnet pole and traditional magnet shapings, T-type magnet pole exhibits significant potential to achieve low torque ripple, high electromagnetic torque, and low magnet usage simultaneously.