Improved stator design for an ultra-high speed spinning ball motor

The ongoing miniaturization trend of electric machines increases the demand for higher rotational speeds to provide a required power level at decreased size. The goal of this project is to push the limits of rotor miniaturization by researching new concepts for bearingless machines with ultra-high rotational speeds exceeding 25 million rotations per minute (Mrpm). Using a simple machine stator consisting of air coils limits the achievable rotor torque, which results in acceleration times of several hours until the aforementioned rotational speeds are reached. This study outlines the torque generation mechanisms of the machine and investigates the stator losses, from which improved stator designs, based on a ferrite core, are derived. The latter significantly increase the motor torque at decreased losses and facilitate fast acceleration of the rotor.