A high speed millimeter-scale slotless bearlngless slice motor

Recent developments in electrical drive systems have shown a trend toward higher power densities at increased rotational speeds with application areas in high speed spindles, turbocompressors, flywheels and reaction wheels as well as optical systems. As conventional ball bearings suffer from excessive wear and decreased reliability at such speeds, contactless magnetic levitation offers an interesting alternative. This work presents the concept, design and implementation of a millimeter-scale bearingless slice motor featuring a rotor diameter of 4 mm. To the knowledge of the authors, this is the smallest published bearingless motor to date. The slotless stator topology is optimized by means of 3D finite element method electromagnetic simulations. Initial experimental results demonstrate a rotational speed of 160 000 rpm at losses below 1W.