Bearingless Segment Motor With Five Stator Elements - Design and Optimization

Bearingless motors and active magnetic bearings work completely contactless and wearless. With these properties, hermetically sealed and lubricant-free rotating systems for various applications can be designed. It is possible to stabilize three degrees of freedom by reluctance forces when a permanent-magnet excited rotor disc is used. Hence, only the remaining three degrees of freedom are actively controlled. A subtype of this constructional design called bearingless slice motor is the bearingless segment motor. This paper comprises the design process of a bearingless segment motor with five equal stator elements and concentrated windings. Finite-element simulations are applied to maximize the bearing forces and the motor torque per ampere and minimize the reluctance forces. However, the mathematical model of the system is nonlinear, therefore, an appropriate nonlinear control scheme has to be applied to put the system into operation. The introduction of a prototype, together with first measurements, completes the paper.