ANALYSIS OF LOSSES DUE TO ROTOR VIBRATIONS IN A HIGH-T-C SUPERCONDUCTING FLYWHEEL SYSTEM

The loss mechanisms associated with the combined effects of magnetic u nbalance and hysteretic damping in a superconducting flywheel system h ave been modelled under the assumption that the dynamic characteristic s of the bearing can be approximated by a linear, elastic isotropic sp ring with structural damping. The theoretical rundown equation of moti on of such systems has been obtained by a Lagrangian approach, neglect ing the effects of angular acceleration. The unknown parameters of the theoretical model have been determined by two different identificatio n procedures starting from experimental time versus rotational speed c urves obtained during rundown tests performed on a plastic flywheel wi th embedded permanent magnet, suspended on a high T-c superconducting stator. In addition to magnetic friction and eddy current losses, the hysteretic nature of the superconducting magnetic bearing gives a sign ificant contribution to the overall losses. Accordingly, the efficienc y of the system can be increased by minimizing the unbalance of the ro tor. (C) 1998 Academic Press Limited.