| Under the background of the exploration of sustainable development in high technologies, high temperature superconducting (HTS) maglev technology will be an important choice for the future of rail transit, characterized by its energy-saving, environmental-friendly, safety, high-speed, comfort and other advantages. In order to promote the first man-loading HTS Maglev test vehicle, successfully developed in China in the end of 2000, from laboratory research to test line demonstrations, the understanding of its performance in the running state is crucial; this dissertation investigated the dynamic levitation characteristics of bulk high temperature superconductors (HTSCs) in a moving magnetic field at different speeds.This research work consists of three main parts. The first part consists of the performance optimization of the HTS Maglev vehicle system. The presented methods not only further optimized the quasi-static interaction between the onboard bulk HTSC and permanent magnet guideway (PMG), but also provided some fundamental bases for subsequent studies on dynamic levitation performances. The second part is about the dynamic levitation characteristics of a levitation system composed of permanent magnet and bulk HTSC at different rotational speeds. The experimental platform is based on a self-developed superconducting magnetic bearing (SMB), and the research method is derived from the present studies on the rotational loss of the SMB. In the last part, an HTS Maglev dynamic test system (SCML-03), developed in 2006, was used to simulate the true running situation of the HTS Maglev vehicle. The levitation force change of onboard bulk HTSCs above the PMG was investigated at different running speeds by the SCML-03. The experimental conditions include the field cooling height, working height, running mode, running time, maximum running speeds, and so on. It must be noted that the moving magnetic field in the second and third parts of this dissertation is different. The main difference is that: in the axis-symmetry SMB system, the applied magnetic field supported by a permanent magnet rotor was very uniform, while in the HTS Maglev vehicle system, the PMG magnetic field had some non-uniformity. As a result, the research work between the two parts is comparable and clear. The main innovation of this thesis is the first investigation of the levitation force performance of a bulk HTSC above a circular rotating PMG, namely the SCLM-03 system, with relative moving speeds of up to 238 km/h which is also the highest experimental speed for dynamic testing on HTS Maglev vehicles up to now. The onboard bulk HTSC working above the PMG mainly was found to undergo three effects due to the inhomogeneity of the PMG magnetic field along the moving direction; hysteretic losses, eddy current losses and delayed shielding current in the high speed conditions. As a result, the levitation force fluctuates and decays during the moving process at high speeds. This decay mechanism of the levitation force was attributed to the declined performance parameter of the bulk which was caused by the heat resulting from the energy loss. Based on the decay mechanism, six methods were presented to suppress the levitation force decay, which were all verified by the experiments. In the end, from the point of application, eight design suggestions, such as assembly techniques of the PMG were provided for future HTS Maglev vehicle system design. These results will be the important scientific bases for the design and testing of the HTS Maglev vehicle test line considerations in the future.
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