Magnetic suspension performance of a bearingless motor/generator for flywheel energy storage systems

This paper presents the magnetic suspension test results of a bearingless motor/generator for flywheel energy storage systems. A prototype bearingless motor/generator is built on the basis of the computed results by Finite Element Method (FEM). It is an outer rotor-type permanent magnet (PM) synchronous motor/generator and the rotor is wrapped by the flywheel (CFRP). Thus, the motor/generator, the magnetic bearings and the flywheel are successfully integrated so that the flywheel system configuration is quite compact. In addition, the coreless stator is employed to decrease the iron loss. The magnetic unbalance pull force is much smaller than that of the cored-stator; as a result, the necessary power for rotor suspension is quite small. It is confirmed by experiments using the prototype machine that non-contact magnetic suspension is successfully realized in the 5-axis.