A.c. magnetic properties of YBaCuO bulk superconductor in high Tc superconducting levitation
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Flywheel
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Rotating magnetic field
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Magnetic Levitation
Rotating magnetic field
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An approach for calculating the interaction between a hard superconductor and a permanent magnet in the field-cooled case is proposed. The exact solutions were obtained for the point magnetic dipole over a flat ideally hard superconductor. We have shown that such an approach is adaptable to a wide practical range of melt-textured high-temperature superconductors’ systems with magnetic levitation. In this case, the energy losses can be calculated from the alternating magnetic field distribution on the superconducting sample surface.
Magnetic Levitation
Spin-stabilized magnetic levitation
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Type-II superconductor
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Levitation of a magnet over a type II superconductor where the field at the superconductor exceeds Hc1 is described and shown. The penetration and pinning of the flux lines in the superconductor cause the position of the magnet to be stable over a flat disk; a complete Meissner effect would make this position unstable. Furthermore, the observed dependence of the height of levitation on such variables as the thickness of the superconducting disk and the size of the magnet are consistent with a model described in this paper based on the energy cost of flux penetration through vortices and inconsistent with a Meissner effect model.
Meissner effect
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The authors present the results of a comprehensive study of the electromagnetic behavior of high-temperature superconducting bulk YBCO exposed to a time-varying magnetic field. The characteristic of the trapped magnetic flux is one of the key factors in the application of a high-temperature superconducting bulk, such as magnetic levitation systems, rotors of motors and bulk magnets. The time inconstancy of trapped flux, such as flux creep, is especially undesirable for its application system. The relationship between a time-varying external magnetic field and trapped flux is investigated experimentally using a field-cooled (FC) YBCO disk. The magnetic flux density just above the disk is measured by Hall probes lined up along the disk radius. The magnetic field decay, which may be independent of flux creep, is observed in the experiment and is influenced significantly by the frequency and amplitude of the AC external magnetic field. The effect of changing rate of applied magnetic field in field-cool process on trapped flux is also investigated experimentally.
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Magnetization forces between small permanent magnets and bulk high Tc superconducting ceramic materials have been measured and show marked hysteretic behavior as a function of the distance between the magnet and superconductor. Magnetic forces of up to 2500 dyn, both normal and tangential to the superconductor surface, have been made. Near-reversible forces are obtained for small motions of the magnet, however, which are believed to be related to flux pinning.
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Maglev
Flywheel
Magnetic Levitation
Spin-stabilized magnetic levitation
Electrodynamic suspension
Superconducting electric machine
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We calculate the current and field profiles in a finite cylindrical type-II superconducting sample which result from displacing it within the magnetic field created by a coaxial permanent magnet. The method of calculation is based on minimizing the magnetic energy in the superconductor, by introducing currents with a maximum density, following the critical-state model. The effects of the superconductor finite size are fully incorporated in the calculations. The levitation force of such a system is calculated from the previous results.
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We have observed the stable suspension of superconductors at 4.2 K below a permanent magnet; the superconductors were the type II material Nb3Sn and the high transition temperature material YBa2Cu3Ox. Suspension below a magnet is to be distinguished from levitation above a magnet, which is the classic demonstration of the Meissner effect. Suspension at 4.2 K can be quantitatively explained as due to complete flux trapping in the superconductor. Suspension has previously been observed only at high temperatures in high transition temperature materials, in which the flux trapping is not complete.
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Meissner effect
Type-II superconductor
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Diamagnetism
Suspension
Magnetic Levitation
Spin-stabilized magnetic levitation
Electromagnetic suspension
Electrodynamic suspension
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