Rotor losses in an ultra-high speed spinning ball motor

The ongoing miniaturization trend of electric machines demands for higher rotational speeds to provide a required power level at decreased size. The goal of this project is to push the limits of miniaturization by researching new concepts for bearingless machines with ultra-high rotational speeds exceeding 25 million rotations per minute (Mrpm). The employed sub-millimeter size spherical solid steel rotors are accelerated by the principle of a solid rotor induction machine. This study presents an analysis of the resulting eddy current losses and a thermal model of the rotor. The temperature of the rotor material is of interest, as it influences the achievable rotational speed at which failure of the rotor due to centrifugal loading occurs.