Aspects of passive magnetic levitation based on high-T{sub c} superconducting YBCO thin films
Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here the authors present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T{sub c} superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, the authors investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation.
- Research Organization:
- National Aeronautics and Space Administration, Houston, TX (United States). Lyndon B. Johnson Space Center
- OSTI ID:
- 135349
- Report Number(s):
- N-96-10230; NASA-CP-3290-VOL-1; S-792-VOL-1; NAS-1.55:3290-VOL-1; CONF-940627-; TRN: 9610246
- Resource Relation:
- Conference: 4. international conference and exhibition of the World Congress on Superconductivity, Orlando, FL (United States), 27 Jun - 1 Jul 1994; Other Information: PBD: Apr 1995; Related Information: Is Part Of Proceedings of the 4th International Conference and Exhibition: World Congress on Superconductivity, volume 1; Krishen, K.; Burnham, C.; PB: [10] p.
- Country of Publication:
- United States
- Language:
- English
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