Critical Current Characteristic Of Composite Superconducting Strands Based On YBCO Coated Conductor

A composite superconducting strands based on YBCO coated conductor is proposed in this thesis which mainly focuses on critical current characteristics in self-field, isotropic property in magnetic field and calculating method of n values as well as AC loss of the strands.Firstly, magnetic field distribution of superconducting strands in self-field is simulated while it carries transport current. According to the empirical formula of the critical current and the magnetic field distribution, the relationship between critical current and operating current is obtained. Then, we design two kinds of short samples whose critical currents are measured in77K and self-field. The results are in good agreement with the calculated ones. After designing several of isotropic composite superconducting strands with different cross-sections, the relationship between critical current and operating current at self-field and external magnetic field are analyzed.Secondly, n value calculation methods of the composite superconducting strands with YBCO coated conductor are described. Circuit model is established based on the cross-sections of composite superconducting strands. We obtain calculation method of composite superconducting strands’n value by using critical current and the n value as independent variables. The method can be also available for determining the n values of the strands or ones formed by more tapes connecting in parallel.Finally, we introduce AC loss characteristics of composite superconducting strands. According to the analysis methods of AC loss in superconducting tapes, we simulated the AC losses of the strands in77K in self-field. Thus, AC loss experiment of short samples is carried out in77K in self-field, it is indicated that the simulating methods are reasonable by comparing calculated results with measured ones.