Ac losses in superconducting magnet suspensions for high-speed transportation

Abstract

A rather general relation is derived between vertical accelerations of the train and cryogenic power dissipation due to ac currents induced in the superconducting suspension magnets. Our theoretical results account for the order of magnitude of the rather large losses observed in the Fuji Electric test vehicle, which used less than state-of-the-art conductors. Even with parameters estimated to represent the best commercially available materials, however, it appears that these losses may be comparable with the total heat leak due to all other causes if the accelerations are as large as permitted by subjective human ride quality considerations. Empirical data on losses under appropriate conditions of B, Ḃ, and I/Ic may be needed to ascertain whether improved materials will be required to avoid serious design constraints by cryogenic heating.