Design variants of the bearingless segment motor

Bearingless drives and magnetic bearings allow the construction of contactless, wearless and lubrication-free rotating systems. Utilizing a permanent magnet excited rotor disc permits the passive stabilization of three degrees of freedom (tilting and axial deflection) by reluctance forces. Hence, using these bearingless slice motors it becomes possible to design very compact magnetically suspended drive systems. The bearingless segment motor is a subtype of the bearingless slice motor, where the stator consists of single elements. As a matter of fact, all these stator segments are magnetically decoupled from each other. This article introduces different designs of the announced bearingless segment motor featuring different rotor and stator compositions. Especially the differences in the generation of bearing forces are outlined. The special features of the various considered drives are examined and their advantages and drawbacks are discussed. Finally these motors are compared qualitatively by different criteria (like the demands on power electronics, passive stiffnesses or bearing force and motor torque capacity).