Study On Loss Characteristics Of Typical Structure Of High Temperature Superconducting Coil

Since the zero resistance characteristic of high temperature superconductor was found,high temperature superconductor has become a research hotspot in the field of electrical engineering because of its excellent electrical properties.HTS coil is the core component of superconducting power device.Its AC loss is an important factor affecting the design and development of high-performance,miniaturized and lightweight HTS power equipment.Therefore,the research on AC loss of HTS coil is of great significance.In this paper,the factors affecting the AC loss of HTS coils with different structures under different environmental conditions are explored.Firstly,the research status of AC loss of HTS coil at home and abroad is summarized,the three basic physical characteristics and critical state mathematical model of superconductor are introduced,and the generation principle and classification mode of AC loss of HTS coil are summarized,which provides a theoretical basis for the construction of superconducting coil simulation model and the Research of AC loss characteristics of HTS coil.Secondly,the two-dimensional axisymmetric models of three kinds of HTS coils with different structures,i.e.single pie coil,double pie coil and double pie coil,are established under the same amount of superconducting tape.By changing the frequency and amplitude of the applied magnetic field,the characteristics of strip stacking and pie coil are studied,and the HTS coil structure with the lowest AC loss under different working conditions is obtained.Through the comparison of simulation results and theoretical analysis,the overall performance of double single cake coils is the best.It provides a reference for the design of HTS coil structure under the condition of quantitative superconducting tape.Thirdly,the main parameters affecting the AC loss of double single cake coils are deeply studied.The influence of coil turns,inter turn spacing and coil radius on AC loss is explored.The results are analyzed theoretically to clarify the main reasons for the change of superconducting coil loss caused by three structural parameters.The results show that the magnetization loss of multi turn superconducting coil is mainly concentrated in hysteresis loss.In a certain range,the more turns of the superconducting coil,the smaller the magnetization loss,and the inter turn spacing and coil radius are positively correlated with the magnetization loss of the HTS coil.Then,the efficiency of finite element simulation under two-dimensional axisymmetry is improved by the principle of homogenization model.The homogenization model is used to optimize a single single cake coil,and the construction process of homogenization model and the loading mode of transmission current are described in detail.At the same time,the dependence of AC loss on the amplitude and frequency of transmission current is analyzed.By comparing and analyzing the single piece and single cake coil model and homogenization model in ordinary 2D,the similarities of the two models and the advantages of homogenization model are confirmed in terms of calculation time,distribution accuracy and so on.Finally,the critical current and AC loss experimental platform is built,the critical current value of superconducting strip and the AC loss value under different working conditions are tested,and the test results are summarized and analyzed.Two superconducting coils with different structures were prepared with the second generation superconducting tape.The accuracy of the experimental data and the feasibility of the experimental method were verified by comparing the experimental data with the simulation results.The causes of the error between the experimental results and the simulation results are analyzed.A series of improvements are made to the experimental platform of AC loss,and the experimental effect is significantly improved.It has a certain reference value for the follow-up study of AC loss of HTS coil.