Dynamics and relaxation of magnetic stress between magnet and superconductor in a levitation system

Abstract

The force of levitation experienced by a magnet on top of' a superconductor depends on position and how fast the magnet was put into that position. As a result, when the levitation force is measured as a function of the height of the magnet above the superconductor, a plot of the force versus height also depends on the rate at which the magnet position was changed during the experiment. We have measured this dependence of the levitation force (as a function of position) on the average rate of moving the magnet towards the superconductor under zero field cooled conditions. This dependence is appreciable only when the magnet is close to the superconductor. After the magnet is brought to a stop a t the nearest position, we continued to observe the relaxation of the magnetic stress between the magnet and the superconductor. The gross characteristics of the relaxation process after the magnet stops are similar for different speeds of approach before the magnet stops. This study aims a t determining how the long term reliability of a superconductor magnet bearing depend on the process of setting it up.

Influence of the lateral movement on the levitation and guidance force in the high-temperature superconductor maglev system

“…It has been accepted that the bulk superconductor is not in a really stable state after the drop; that is, the levitation force has a logarithmal decrease with time. [6][7][8] This phenomenon defined as levitation force relaxation has been investigated experimentally and theoretically. But most of their systems composed of the superconductor and magnet were coaxial 9 and there was no movement during the measurement.…”

Experimental observation of a crossing in the force–displacement hysteretic curve of a melt processed YBaCuO bulk superconductor

“…Because of the unsaturated magnetic field, the crossing originates from the magnetic hysteresis of the YBaCuO bulk superconductor with high critical current density. [19]. The maximum levitation force of Sample B at a speed of 20 mm/s is 5.7 N, which is the minimum value for all the measurements.…”

“…Moreover, it is well known that the levitation force between a superconductor and a magnet is not only related to the electromagnetic properties of the superconductor, but also to the thickness and shape of the samples [14], initial cooling process [15,16], operating temperature [17], grain-orientation [18] etc. Postrekhin et al [19] reported the dependence of the levitation force on the average speed of moving the magnet (up to 12 mm/s) towards the superconductor and found that the maximum levitation force increased with increase in the moving speed of the magnet. In this work, we used an updated high temperature superconductor maglev measurement system [20] and measured the effects of the moving speed of the magnet (up to 20 mm/s) on the maximum levitation force of a melttextured superconductor.…”

Influence of Waiting Time on the Levitation Force Between a Permanent Magnet and a Superconductor

“…[21][22][23][24][25] But there are few reports about the influence of waiting time on the levitation force in literature. In this work, we report a study of the influence of waiting time on the levitation force between a PM and FC and ZFC YBaCuO bulk superconductors.…”