Concept of a 150 krpm bearingless slotless disc drive with combined windings

In this paper, a concept is developed for a slotless bearingless disc drive with toroidal windings for a rotational speed of 150´000 rpm. The topology and its working principles are explained and an already running prototype for lower speeds is introduced. To reach the high rotational speeds, the mechanical strength and the maximal diameter of the rotor is evaluated. Outgoing form the prototype, scaling laws are examined to identify the challenges for down-scaling of the bearingless motor. 3D FEM Simulations and optimizations are conducted to determine the influence of the magnetic gap length and to find the optimal stator and rotor height. At the end, the geometry of the high speed concept is presented and the performance results are compared to the prototype.