Static And Dynamic Study Of High Temperature Superconducting Maglev And Its Optimization And Design Methods

High-Tc Superconducting (HTS) levitation uses the intrinsic flux-pinning effect of a bulk superconductor to achieve passive levitation above a permanent magnet without active control. This technology has a wide application prospect, e.g., HTS magnetic levitation bearings and HTS maglev. In the year 2000, the world's first man-loading HTS maglev testing vehicle'Century'had been successfully developed at the Appilied Superconductivity Laboratory (ASCLab), Southwest Jiaotong University. This achievement gave a solid evidence that this technology can be applied in the transportation system. During the following 8 years of researching, ASCLab had conducted a thorough experimental and theoretical investigation of the HTS maglev system, publishing more than one hundred scientific papers. However, many unconsidered and unsolved questions still lie ahead. In order to fasten the pace of commercialization of the HTS maglev, this thesis dealt with several undetected questions in the application of HTS maglev and HTS bulks, through both experiment and theory. Furthermore, optimization methods and design theories have been proposed.In the practical running of the'Century', we found that while the passengers constantly embark and disembark the vehicle on one side, the vehicle body will suffer a slight but unrecoverable slanting angle. In order to deeply understand this phenomenon, a simplified HTS maglev model was used to study the change of dynamic responses while it was under side-loading, and compare it with the center-load condition. Meanwhile, the slanting angle during side-loading was gauged and its residue angle after undoing the load. In the end, the feasibility of using'pre-load'methods to enhance the performance was tested with positive results.Due to the inability to control the levitation of the HTS maglev, a method to wind a copper coil around YBCO bulks was proposed. By changing the DC current in the coil, the overall levitation performance was adjusted:while the coil was positively powered-up (repulsive force between permanent magnetic guideway), the levitation system's levitation force increased, but the guidance force decreased; while negatively powered-up (attraction force between permanent magnetic guideway), the system's guidance force increased, but the levitation force decreased. Therefore, we can choose the direction and the amount of the DC current to help adjusting the HTS bulk's levitation in different conditions. Meanwhile, the presence of the coil's magnetic field could influence the performance of the HTS bulks, this influence is explained by Bean's Critical Sstate model. This hybrid levitation method had not been reported before.When HTS bulks are moving down above a permanent magnetic guideway at different speeds, the levitation force will vary. Through experiments, the tendency of the maximum levitation force while the YBCO bulks moving from field-cooling height to the working-height have been summarized. A simplified R-L superconducting ring and flux flow model was adopted to simulate this behavior, the calculation results were found to fit well with experimental data. Through computational calculations, the variation of the maximum levitation force was found to be connected with the internal thermo-dissipation of the superconductor. The faster the moving speed, the smaller the thermo-dissipation, and the maximum levitation force is more likely to increase and approach the zero-dissipation case. This research will help deepen the understanding of HTS bulks'quasi-static behavior in applied magnetic field and provide theoretical roots for the practical design of HTS levitation devices.The HTS maglev system is still in the laboratory scale, there are no existing curve design theories for the HTS maglev. Therefore, in combining with the HTS bulks'levitation force and guidance force characteristics, and the provailed curve theory for the wheel-track system, a curve design method for the HTS maglev is proposed. This method consists of designing and employing a circular curve at low speeds, while not elevating the outer rail; in high design speed, elevate the outer rail, and according to the hysteresis curve of the levitation force, design of the'downward adjusting curve'and the'upward adjusting curve', respectively, can be implemented. This design method has not been reported before.This thesis'researching contents concern on solving practical problems of the HTS maglev system. Through the research of these problems, the HTS levitation theories could be further improved, and could also provide methods and roots towards more practical designs.