© 2016 IEEE IEEE Transactions on Magnetics, Vol. 52, No. 7, July 2016 Characterization of Electromagnetic Rotor Material Properties and Their Impact on an Ultra-High Speed Spinning Ball Motor M. Schuck, T. Nussbaumer, J. W. Kolar This material is published in order to provide access to research results of the Power Electronic Systems Laboratory / D-ITET / ETH Zurich. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the copyright holder. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.