A high-speed superconducting motor / generator demonstrator is currently being built at Robinson Research Institute. This will enable applications such as flywheel energy storage systems, direct-drive generators and high-speed microfans to be explored whilst also providing the opportunity to demonstrate key technology elements such as flux-pumped REBCO field windings and low-loss high-speed bearings. Superconducting magnetic bearings appear to be a solution for overcoming the speed limit imposed by conventional bearings in any motor / generator. Although offering contactless movement, superconducting bearings are not totally loss-free. AC loss, mainly caused by magnetic field inhomogeneity in superconducting bearings, has been considered as a figure of merit for assessing performance. Although much effort has been done to measure and formulate the AC loss, its mechanism has not been fully explored and determined. Here we report on the commissioning of a kHz-rated horizontal bearing test-rig to understand the relationships between magnetic field inhomogeneity, frequency and AC loss, and to explore the development of suitable low-loss bearings from bulk REBCO superconductors.

Keywords: High speed superconducting motor, Maglev bearings, AC loss, Spin down test