Research And Analysis Of Electromagnetic Characteristics Of Roebel Superconducting Composite Conductor

The application of high temperature superconducting materials in power technology can not only meet the goal of carrying large transmission current,but also greatly reduce the energy loss,improve the efficiency of operation and relieve power supply pressure.However,the application of high-temperature superconductors in high-capacity superconducting power equipment is far beyond the bearing capacity of a single superconducting tape.At the same time,the AC loss of high-temperature superconductors under alternating current or magnetic field will produce large heat,which will affect the operation stability and even safety of superconducting equipment.In general,the simple parallel connection of superconducting tapes can improve the current carrying capacity to a certain extent,but the multiple parallel connection of superconducting tapes will lead to uneven distribution of current and high AC loss.Therefore,it is very important to study superconductors with high current carrying capacity and low AC loss.In this thesis,the critical current and AC loss of HTS tapes in self field are studied,and the critical characteristics and AC loss characteristics of stacked conductors and Roebel superconducting composite conductors are studied.In this thesis,the classification of superconducting materials and the basic theory of superconductivity are described,and the critical state model of superconductors is described based on the superconductivity phenomenon;Then,the classification,generation mechanism and some calculation models of AC losses of superconducting materials are explained;Based on Maxwell equations and constitutive equations,the numerical calculation method of AC loss,H-equation,is deduced and demonstrated.Based on H-equation finite element analysis method,the electromagnetic characteristics and self-field loss of HTS tapes are analyzed,and the AC loss is compared with the calculation results of Norris model;Then,the electromagnetic distribution,critical characteristics and AC loss characteristics of stacked conductors composed of two8 mm superconducting tapes and four 4 mm superconducting tapes are studied.The AC loss of each single tape with the same current or the same total current is analyzed and studied under different number of stacked tapes.Based on the three-dimensional model of Roebel conductor,the structure of Roebel conductor is analyzed,and the arrangement between strands of Roebel model in modeling is described in detail;Taking 10 strand Roebel superconducting composite conductor as an example,the electromagnetic characteristics of single strand strip and Roebel conductor are studied;Secondly,the influence mechanism of structure parameters(dislocation length,angle,transposition structure,gap between strands in vertical direction,single strand width)and frequency on AC loss characteristics of Roebel conductor is studied;Finally,the AC losses of stacked conductors,parallel stacked conductors and Roebel conductors under the same current carrying capacity are compared.Finally,based on Labview control program,the critical current test platform is built,and the critical current of 4 mm wide superconducting narrow band and 10 mm wide superconducting wide band is measured,and the E-J characteristic curve is fitted;An AC loss measurement platform based on phase-locked amplification method is built.The AC loss characteristics of 4 mm and 10 mm superconducting tapes,8 mm wide superconducting tapes,two 8 mm wide vertical stacked conductors,four 4 mm narrow parallel vertical stacked conductors and four Roebel conductors are measured.The experimental results are compared with the finite element simulation results to verify the accuracy of the simulation model and the test platform.