Rotation speed degradation of superconducting magnetic bearing made of unsymmetrical shaped YBCO bulks

Abstract

The radial-type superconducting magnetic bearing (SMB) system consists of the superconducting stator (SC stator) and the permanent magnet rotor (PM rotor). The rotation speed degradation of the PM rotor is one of the most significant problems for the practical use of SMB to the energy storage flywheel system. This phenomenon is caused mainly by the eddy current in the PM rotor induced by the inhomogeneous magnetic field which is weakened at the joints between the YBCO bulks. In this research, the rotation speed degradation and the rotation energy loss were simulated, and their suppression effect was evaluated by the 3-dimensional superconducting current simulation code based on the current vector potential method (T-method) and the vector potential method ( A– ϕ method) [K. Demachi, R. Numata, R. Shimizu, K. Miya, H. Higasa, J. Mater. Process Technol. 108 (2001) 141].