Tests with a hybrid bearing for a flywheel energy storage system

This paper describes the design and experimental test of a passive magnetic bearing system composed by a superconductor magnetic bearing (SMB) and a permanent magnet bearing (PMB). This bearing setup is part of a flywheel energy storage system. The advantage of using a passive bearing system is that it offers low friction without the need of a magnetic bearing controller, increasing the reliability and decreasing the energy consumption. The first set of tests were quasi-static radial and axial force measurements of the PMB operating alone and together with the SMB. As the PMB is intrinsically unstable in one degree of freedom, the operation of the SMB together with the PMB is necessary to stabilize the system. After that, dynamic measurements were made for the SMB operating alone and together with the PMB. The resonant speeds were identified and the bearing radial and axial forces were also measured for the SMB and SMB + PMB operation. These results indicate that the studied bearing set is technologically feasible to be used in flywheel energy storage systems.