Bearingless Segment Motor with Buried Magnets

Bearingless motors combine contactless levitation and rotation in a preferably compact system design, because the bearing as well as motor windings are located on the same lamination stack. 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 diameters. However, most of the bearingless motors are designed with surface mounted permanent magnets on the rotor, neglecting the advantages of buried permanent magnets. In this paper a bearingless segment motor with buried permanent magnets is investigated. The mathematical model is presented, a proper control scheme is introduced and the optimization of the prototype motor is outlined. Some motor specific considerations concerning the angular sensors and the rotordynamic are also 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.