| Superconducting generator is a new type of machine structure in the field of electrical machine. It has many advantages, such as large power density, small synchronous reactance, high efficiency, easy maintenance etc. It was considered the most potential and ideal of energy conversion device in this century. However, superconducting generator has such advantages because superconducting magnets are included. Therefore, if they can work well, superconducting magnets have a consequential effect on the success or failure of a superconducting generator. Superconducting magnet(SM) in a 50 kW superconducting generator was studied in this paper. First of all, the electromagnetic properties and application principle of SM were analyzed in the generator, and the suitable superconducting material was choosed by according to the basic characteristics of superconducting material and the actual situation. Secondly, the electromagnetic design of SM was performed and an optimization algorithm was proposed to optimize structure of SM, and then the design of the cryogenic system was carried out in order to provide low temperature environment for SM. Finally, the SM was made by the optimized size, and the testing platform was set up. It was verified that the designed SM met the requirements or not by experimental method in this paper.The results of this thesis are as follow:● The zero resistance characteristic and the meissner effect of superconductor were deduced by analyzing the electromagnetic properties equation of superconductor. The calculation method of any point in magnetic field was obtained by selecting on the basis of the current density for the different kinds of SM. The characteristics of superconducting generator were obtained by analyzing the different types of superconducting generator. For different applications, the requirements of superconducting material are also different. According to the cost, complexity, performance of generator and the characteristics of the five kinds of superconducting material, the MgB2 superconducting material was selected as the field windings of superconducting generator. The adaptability and reliability of the MgB2 superconducting material were demonstrated in this paper.● Superconducting generator has four kinds of basic structure. Their working principle was analyzed and their advantages and disadvantages were compared. The basic structure of the prototype was determined. Based on the electromagnetic characteristics of the selected MgB2 superconducting coils, the electromagnetic design of SM was performed by according to the design requirements of the propotype. The initial structure parameters of the SM were determined by a large number of simulation calculations. It was obtained that the performance parameters meet the design requirements by analyzing the performance of the prototype. Therefore, it was verified that the SM met the requirements of this subject by the simulation calculation.● It was analyzed in detail that the structural parameters of superconducting magnets were the effect of the performance of the prototype. In order to give full play to the advantages of SM and obtain the better performance of superconducting generator, this paper proposed an optimization algorithm which is the combination of response surface method (RSM) and particle swarm optimization (PSO) to optimize the structure of SM. An optimizing process for the structure of superconducting magnet was given in detail according to the proposed optimization algorithm, and the feasibility and effectiveness of the proposed optimization method were verified by comparing the initial and optimized results.● A suitable cooling medium was selected by comparing the advantages and disadvantages of several common cooling medium. The advantages and disadvantages of several cooling methods were analyzed. The suitable cooling method was choosed by considering their cooling effect, system complexity, cost, and the choice of cooling medium. A suitable vacuum was chosen by analyzing the thermal conductivity of the cylinder vacuum. The basic scheme of cryogenic system was determined.● A SM was made by the optimized size, and a testing platform was set up, and then the normal temperature test and the cooling test of SM were performed. The normal temperature was obtained by the normal temperature test. Four cooling test were carried out. The previous three experiments were failure. The critical temperature and the critical current were obtained by the fourth test. The critical current far less than that of MgB2 superconducting material as the performance of superconducting material which was provided by manufacturer was poor. Although these experiments were unable to verify the designed superconducting magnet met the requirements or not, they provided experimental experience for the follow-up test of SM. |
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