Temperature Dependency of Levitation Force and Its Relaxation in HTS

Abstract

High-temperature superconductors (HTS) have high potential for various engineering applications such as a superconducting flywheel energy storage system. The attractive feature of the superconducting magnetic bearings in the energy storage system is a reduction in the rotational loss. In this study, we studied the feasibility of a superconducting magnet to support bulk superconductors in magnetic bearings with the aim of increasing the stored energy. The superconducting magnet has a room temperature bore of 100 mm with the maximum magnetic field of 3.5 T. In addition, we used a GM freezer (10 K in the lowest attainment temperature), which can control the temperature of the bulk superconductors. The used bulk samples were Y-Ba-Cu-O and Sm-Ba-Cu-O 46 mm in diameter and 15 mm in thickness fabricated with a top-seeded melt-growth process. We have studied the effects of the temperature and magnetic field on the levitation force and its time relaxation. The levitation forces were measured by applying the magnetic fields of 0-2 T at 10-77.3 K. It was found that the levitation force increased with lowering temperature in both samples. The time relaxation of the levitation force was also reduced with lowering temperature. Sm-Ba-Cu-O exhibited better performance in the levitation force and its time relaxation in a high temperature and high-field region.

Numerical study of the influence of flux creep and of thermal effect on dynamic behaviour of magnetic levitation systems with a high-Tcsuperconductor using control volume method

“…The numerical code is examined a second time in order to predict the experimental phenomena which arise when the temperature is increased and thus the force is reduced [8]- [10]. This effect can be observed for example in the dynamic response of the levitation behaviour [8]- [10]. First, some basic simulations are made to show if the influence of the superconductor's temperature on the levitation behaviour is notable.…”

“…which expresses the thermal flux exchange between the superconductor and the cryogenic fluid. In (10), h is the convective heat transfer coefficient.…”

“…In practice, the temperature influences the dynamic magnetic force's characteristics of the superconductor. For instance, T. Suzuki and al [8]- [10], studied experimentally the effects of the temperature on the levitation force and the time relaxation. They found that the levitation force and the time relaxation of the levitation force decreased with increasing temperature.…”

Relaxation Properties of the Trapped Flux of Bulk High-Temperature Superconductors at Different Magnetization Levels

“…Although the relaxation decay is mostly found to show a logarithmic time dependence [8], any decay may degrade the performance of superconducting magnetic devices, and finally involve potential influences on the operation stability. From this viewpoint, the magnetic relaxation phenomenon has aroused great attention of worldwide researchers and formed a crucial and intense topic accompanying the engineering applications of bulk HTS [8][9][10][11][12][13].…”

A rotor model with two gradient static field shafts

“…One is a storage system by the flywheel [1,2]. The other is the motor used for the ship [3] or the airplane [4].…”