2D analytical torque study of slotted high-speed PMSMs considering pole pairs, slots per pole per phase and coil throw

Abstract

Recently the interest in permanent-magnet syn-chronous machines (PMSMs) operating at high speed has grown. However, a lot of design and operation questions remain unan-swered. This work aims at studying the effect of the number of pole pairs, the number of slots per pole per phase and the coil throw on the torque and the torque ripple in high-speed PMSMs. High-speed machines are often equipped with a shielding cylinder, i.e. a conductive sleeve wrapped around the magnets. The study is therefore performed using a 2D analytical subdomain model that accounts for slotting and the eddy-current reaction field. The classical torque component and the torque due to interaction with the eddy-currents in the shielding cylinder are regarded separately. I. INTRODUCTION Because of three reasons, high-speed Permanent Magnet Synchronous Machines (PMSMs) have recently gained a lot of attention. The first reason is their possibility to drive high-speed applications in a direct-drive configuration. This implies eliminating the losses and the maintenance related to the gear-box. Secondly, machines designed for high-speed operation are characterized by a high power density. They are therefore ideal for applications with space or weight restrictions. Finally, because of their limited dimensions, the required amount of rare-earth magnets is low when compared to conventional PMSMs. The great interest in high-speed electrical machines has re-sulted in a large number of publications related to such machines [1]–[4]. However, there are still a lot of questions as to what machine topology is best suited for machines operating at high speed.