Study On Levitation Characteristics And AC Loss Of Stacked High Temperature Superconducting Tapes

Compared with traditional high-temperature superconducting(HTS)ceramic bulks,HTS tapes have higher critical current density,stronger pinning ability and mechanical strength and can be stacked to form a superconducting bulk-like structure,which is used in a HTS magnetic levitation system.Quasi-static levitation force,guiding force and levitation force relaxation characteristics are important mechanical characteristics for studying the performance of HTS magnetic levitation systems.At the same time,the AC loss and temperature rise characteristics of the stacked HTS tapes are factors that must be considered for its application.Therefore,this paper analyzed the mechanical properties of stacked HTS tapes in magnetic levitation system and their AC losses and temperature rise characteristics under an alternating external magnetic field,and the application principles of stacked HTS tapes are analyzed.First,the nonlinear power exponent E?J relationship and the improved Kim model were used to describe the electromagnetic characteristics of the superconductors.Based on the moving mesh function and the multi-scale meshing method,the magnetic field formula(H)method was used to construct a levitation calculation model of the stacked HTS tapes,and the accuracy of the simulation model was verified.The levitation force of the same size stacked tapes and HTS bulk was further compared and analyzed.Subsequently,the effects of the number of the stacked layers,critical current density,and the combination of stacked tapes on the levitation characteristics were further analyzed.The results show that increasing the number of the stacked tapes and critical current density can improve the levitation force of the stacked HTS tapes to a certain extent.A single stacked HTS tapes module cannot have both levitation force and guiding performance on a permanent magnet track,so a combination scheme of multiple stacked HTS tapes module is proposed,and ideal levitation force and guiding performance are obtained.Secondly,based on the coupling of the PDE interface and the solid heat transfer module in the Comsol finite element software,the electromagnetic thermal coupling model of the stacked tapes module under a vertical alternating external magnetic field was established.The accuracy of the model was verified by comparing the current distribution,magnetic field distribution and AC loss of a single HTS tape with Brandt's theory.Then the simulation module was extended to the stacked tapes module,and the effects of stacking layer number and stacking spacing on the electromagnetic characteristics and AC loss of the entire stacked tapes module were studied.At the same time,the temperature distribution in the stacked tapes model was studied.The results show that due to the proximity effect,the complete penetration magnetic field and AC loss of the stacked HTS tapes are negatively correlated with the number of the stacked layers and positively correlated with stacking spacing.Meanwhile,the temperature distribution of the stacked tape module is determined by the AC loss and heat exchange process.The temperature rise inside the stacked tape module is obvious,and the temperature distribution is uneven under a large external magnetic field.