A New Design Approach Of An Ultra High-Speed Permanent Magnet Synchronous Motor (PMSM) System

This paper introduces a new design scheme of an ultra high-speed permanent magnet synchronous motor (PMSM) that enables utilization of an open-loop control. Theoretical analyses and both simulation and experimental results validate the proposed design technique and its effectiveness. Employing permanent magnet Nd-Fe-B, a PMSM offers the advantages of high efficiency and high power density compared to other types of motors. By using slotless stator structure, the cogging torque due to the slots is eliminated, and losses caused in the rotor surface are also eliminated. However, most PMSMs are inherently unstable and correspondingly require a closed-loop control system or damper windings in the rotor to assure the synchronization of motion of the rotor with the stator frequency applied. Design of a closed-loop control system is technically very challenging since a feedback sensor such as an optical encoder or a hall sensor is not reliable at ultra highspeed of 200,000 rpm. The ultrahigh speed PMSM system achieves 90.7% efficiency at 200,000 rpm while the stability of the motor can be guaranteed over its operating speed range under the open-loop controller.