Bearingless Segment Motor with Buried Magnets

Abstract

Bearingless motors combine contactless levitation and rotation in a preferably compact system design, because bearing as well as motor windings are located on the same lamination stack. The bearingless slice motor features comparatively low complexity for a fully magnetically levitated drive system, because it allows the passive stabilization of three degrees of freedom by reluctance forces. By the use of a proper control scheme and the superposition of different current components, bearing forces and motor torque can be generated simultaneously by applying concentrated windings. This leads to a further simplification of the mechanical configuration. The bearingless segment motor features such concentrated coils on separated stator elements, which reduce the stator iron and therefore weight and cost, especially for constructions with large diameter. However, so far all bearingless slice motors are designed with surface mounted permanent magnets on the rotor, neglecting the advantages of buried permanent magnets. In this paper a novel bearingless segment motor featuring a rotor with buried permanent magnets is investigated. The motor specific mathematical model of force and torque generation is presented, a proper control scheme is introduced and the optimization of the prototype motor is outlined. Motor specific considerations concerning the angular sensors are given. Finally, the performance of the bearingless segment motor with buried permanent magnets is shown by the comparison of simulation results with measurement data of the manufactured prototype.