Simulation Research Of AC Loss About Joint In YBCO Coated Conductor

The joint structure plays a crucial role in the practical application of high-temperature superconducting tapes.Its electromagnetic and mechanical properties relate to the stable operation of the entire superconducting power device.How to make a joint with good electromagnetic performance is very important to stabilize the superconducting power device.Research on the transmission characteristics of superconducting joints has always been a fundamental issue in the theoretical and engineering applications in this field.The current experimental researches are mostly from the viewpoint of production and welding,and they are dedicated to improving the electrical and mechanical properties of superconducting joints,and constantly optimizing to reduce the resistance and strength defects caused by the joints,and the finite element of the electromagnetic behavior of the joint structure.The analysis can clearly define the distribution of the internal current and the AC loss of the connector,and lay a theoretical foundation for the application of the superconducting joint in the coated conductor.In this paper,the electro-magnetic behavior of an alternating current in a field is studied numerically,aiming at the lap joint of a YBCO coated conductor(CC).Firstly,based on the Maxwell equation,the control equation describing the electromagnetic behavior of superconductors is deduced by studying the general E-j Power law of superconductors,which is solved by H method.And then use the COMSOL simulation software establishes a two-dimensional model of the YBCO HTS Strip,analyzes the distribution of the magnetic field intensity and current density of the superconducting strip in the field of the alternating current,and calculates the AC loss under the field transmission Finally,a three-dimensional simulation model is set up to study the AC loss of high TC superconducting strip lap joint in the field of AC power transmission.The influence of the length of the joint and the frequency of the transmission current on the field is analyzed,and the distribution of the magnetic field,current and AC loss of the superconducting layer and weld layer inside the joint and the joint structure is analyzed.The results of the research show that with the increase of the alternating current frequency of the superconducting joint,the loss of the field is increased,and the growth ratio of the field loss is almost the same as that of the frequency.In addition,by increasing the overlap length size of the joint,it can reduce the joint AC loss.After analyzing the distribution of magnetic intensity and current density,it is found that the superconducting joint transmits the alternating current mainly through the superconducting layer and has a strong edge effect in the superconducting layer: the density of the edge region along the length direction is large,the density of the middle region is relatively small,and the amplitude of the transmission is increased,The main current transmission region spreads from the edge of the superconducting layer to the center of the superconductor.