A permanent-magnet rotor for a high-temperature superconducting bearing

Design, fabrication, and performance of a 0.39-m diam., 6.8-kg flywheel rotor with only one bearing is discussed. To achieve low-loss energy storage, the rotor's segmented-ring permanent magnet (PM) is optimized for levitation and circumferential homogeneity. A PM figure of merit is proposed that appears to correlate with loss data. Pre compression of the PM with fiber-composite banding is necessary for practical rotor speeds.