Bearingless Slice Motor Systems without Permanent Magnetic Rotors

Magnetically levitated drives have no mechanical contact during operation. This brings numerous advantages, such as no wear, long lifetime, low maintenance, reduced vibration, no need for lubrication and sealing, inherent process monitoring, high-speed capability and possible hermetic separation of rotor and stator. Hence, long-lived, ultra-pure, environmentally friendly and highly reliable applications become feasible. However, the force density in magnetically levitated drives is limited. Even more problematic is the high initial system cost, as these devices require additional sensors, actors, power electronics and digital control, which may be an obstacle to their broad industrial application. The bearingless slice motor is a very compact and therefore economical means of realizing a fully magnetically levitated drive. The disk shape of the rotor is essential, as it enables passive stabilization of three degrees of freedom by means of reluctance forces. This stabilization also requires a magnetic bias flux in the air gap, which is typically realized by rotor permanent magnets. However, particularly in disposable systems, where the rotor must be replaced frequently, the high cost of permanent magnetic material is problematic. High temperatures and material stress impose strict limits on permanent - orderid - 26936021 - transid - 26936021_1D -magnetic rotors. Against this background, this work focuses on novel bearingless motors in which the rotors contain no permanent magnets.