Design of an Ultra-High Speed Bearingless Motor for Significant Rated Power

Abstract

The goal of electric motor technology is to deliver maximum power in as compact of a form factor as efficiently and reliably as possible. Recent advancements in magnetic materials and semiconductor devices are enabling a new class of electric motors which utilize ultra high rotational speeds (100,000+ RPM) to increase power density. The technology is limited by shortcomings related to motor bearings, primarily insufficient lifetime and rotor dynamics that limit the speed-power capability of the electric machine. This paper investigates the design of a magnetically levitated, ultra-high speed motor based around a bearingless permanent magnet motor topology to solve these challenges. The design targets a speed-power capability of 160,000 RPM and 5.5 kW for a hydrogen fuel cell compressor. This rating is amongst the highest speed-power designs that utilize conventional bearings and would expand the limits of speed-power rating of a bearingless motor. A detailed multi-physics modeling framework is developed and coupled to a multi-objective optimization algorithm to explore the design space. An optimal design is proposed and investigated for prototype fabrication. Experimental validation of the modeling framework is provided with low speed and stationary test results.