Effect Of YBCO Wire Structure On AC Loss Of Cylindrical Superconductor

With the rapid development of science and technology and the increase of power consumption,superconducting cables with high current carrying capacity,low loss and small volume are particularly important.However,AC loss will lead to heat generation in superconducting cables,which will increase the cooling cost,resulting in the inability of large-scale use of superconducting cables.Therefore,how to reduce AC loss has always been an important issue in the research of superconducting cables.Superconducting wire is the key material for making cable.The high-temperature superconducting tape of high-temperature superconducting cable is generally a cylindrical structure composed of superconducting wire around the support column.Therefore,the structure of superconducting wire will also affect the magnetic field distribution of superconducting cable,and then affect the AC loss.A new type of high temperature superconducting square wire is developed by narrowing and stacking YBCO wire.Compared with YBCO wire,the magnetic field distribution of square wire tends to be more circular,which can greatly reduce the magnetic field perpendicular to the wire surface.However,the performance of the square wire superconducting cable still needs further analysis.Therefore,this paper will establish a two-dimensional finite element simulation model of the superconductor based on the simulation software COMSOL multiphysics,calculate the simulation model through h equation and E-J exponential equation,analyze its magnetic field distribution,and compare its AC loss.Starting with square wire,the influence of YBCO wire structure on AC loss of superconducting cable is analyzed.In this paper,the research is carried out in the order from easy to difficult.Firstly,the two-dimensional finite element simulation models of three kinds of square wire with 2+4,4+2 and 6+0 stacking structures are established by using the optimized superconducting simulation method.The AC loss of the square wire is measured through experiments,and the experiments are compared with the simulation to verify the correctness of the simulation,and the performance of each wire is analyzed.Then,the simulation calculation of the hexagonal YBCO superconducting cable is carried out,and compared with the experimental data,the AC loss characteristics are analyzed,and the correctness of the simulation method of cylindrical superconductor is verified.Finally,based on the previous research,the simulation models of hexagonal,octagonal,decagonal and dodecagonal square wire superconducting cables are established for calculation.The purpose is to analyze the influence of wire number and wire structure on the AC loss of superconducting cables,and compare the hexagonal YBCO superconducting cables to explore the optimization method of superconducting cables.The results show that 4+2 square wire has the best performance among the three kinds of wires,and 6+0 square wire does not use it to establish the simulation model of superconducting cable because of its deterioration;The simulation results of the hexagonal YBCO superconducting cable are reliable,and the cylindrical structure helps to reduce the AC loss.When the square wire superconducting cable transmits higher current,the AC loss of 4+2 square wire superconducting cable is lower and the current carrying capacity is stronger.The 4+2 square wire superconducting cable is basically consistent with the calculated value of monoblock model.With the increase of the number of superconducting cable wires,the increase of AC loss decreases gradually;Compared with the hexagonal YBCO superconducting cable,the dodecagonal square wire superconducting cable has smaller volume,lower AC loss and stronger current carrying capacity.