The Fabrication Of A Novel Soldered-stacked-square HTS Wire And Study On Its Characteristics

With the development of superconducting technology,superconducting transformer,superconducting energy storage and superconducting cables have been rapidly applied.However,in practical superconducting electric power equipment,wires must experience external magnetic field which would reduce its performance including critical current,ac loss and so on.Several new structures of superconductor wires such as stacking,transposition and twisting are discovered and studied in order to reduce the influence of external magnetic field on superconducting wires.However,with limitations of material properties,the second generation(2G)high temperature superconducting(HTS)wires are entirely based on 4 mm or over 4 mm width,method above is hard to apply.Based on the study,a novel soldered-stacked-square(3S)HTS wire is suggested and developed through narrowing,stacking and soldering processes in this paper.Firstly,the original 2G tape with 4 mm width was incised into four narrow wires with the same width of 1 mm.The critical currents of the narrow wires were tested in liquid nitrogen of 77 K by the four-terminal method.Secondly,several 3S wire samples were fabricated which were made with different number superconducting wires and brass strips.In order to verify the feasibility of the stacking and soldering processes,the electrical properties such as critical current and ac loss were tested and the mechanical properties such as bending diameter,axial tension and twisting pitch were also tested.The results show that the critical current curves of 3S wires are the ones of typical superconducting wires.Compared with the original critical current,the critical currents of the 3S wires are decreased approximately 10% after the stacking and soldering process.The minimum bending diameter for the 3S samples is approximately 60 mm,and the allowable axial tensile force is 350 N,and the minimum twisting pitch is about 65 mm.These electrical and mechanical properties of 3S HTS wire are satisfied for the HTS applications significantly.