Quasi-Static Force Relaxation Characteristics of High Temperature Superconducting Magnetic Levitation

To investigate the quasi-static force-relaxation characteristics of a YBCO bulk levitated above a Halbach permanent-magnetic guideway, using the top-seed-melt-texture-growth method, the complete relaxation process is defined and divided into the excitation process (involved initial state, dynamics process, and termination state), relaxation process, and steady state. With the same initial and termination states, the effect of different displacements of the dynamics process on the steady state is experimentally investigated using a specialized apparatus. Then, on the basis of magnetization and the Anderson-Kim model, a relaxation model is established and several laws are formulated. The results indicate that the steady states of the four displacements tend to be the same. However, the maximum levitation force (MLF) is affected by the round-trip times and displacement velocity. The MLF points are distributed around a curve that decays logarithmically with time. Prior to the relaxation process, the levitation force of the terminating state is positively correlated with the velocity; the steady state results after the relaxation process tend to be consistent. Furthermore, after the relaxation process, the influence of the velocity on the MLF is greatly reduced (the MLF difference decreases from 3.7 N to 2.0 N). Relaxation phenomena are in both the excitation and relaxation processes of superconductors, and the effect of the velocity and round-trip times on the MLF is manifested in the relaxation during the excitation process. © 2023 Science Press. All rights reserved.