Topology evaluation of slotless bearingless motors with toroidal windings

In this paper, different winding and magnet topologies are analyzed and compared for a slotless bearingless disk drive with toroidal windings. Basis of the studies is a six phase motor with a diametrically magnetized one-pole-pair rotor. Due to the absence of mechanical bearings, the motor is suitable for applications with high purity and special chemical demands. Its slotless design results in low losses even at high rotational speeds. To improve the operational behavior of the rotor in different applications, the influence of higher pole pair numbers on the passive bearing stiffness is examined. Possible winding configurations for these rotors are presented and evaluated for their bearing and motor performance. Based on the results, a further prototype was built and is presented in this paper.