Slotless bearingless high speed disk drive designed for speeds beyond 100krpm

This paper deals with the validation and implementation of a bearingless drive for high speed applications up to 100 krpm. To achieve the bearing forces and the drive torque this motor is equipped with 6 toroidal coils that promised, based on previous optimizations, higher power densities than an earlier implemented 5-phase configuration. The rotor of the bearingless drive has to face high centrifugal forces, which are currently limiting the maximum speed of motors of this topology and size. The operation of bearingless drives at high speeds entails a lot of new challenges which could be neglected so far due to the uncritical maximum speed limit. The main goal of the article is to discuss the integration of all necessary steps to accelerate the prototype.