Research On AC And DC Characteristics Of The 2G HTS Strand

With the development of superconducting technology, remarkable progress has been achieved in the mechanical and electromagnetic properties of the high temperature superconducting (HTS) materials. Comparing with other (HTS) materials, REBCO CC is low loss and high current-carrying. The realization of the large-scale commercial production greatly promotes the application of the REBCO CC in HTS cable, transformer, current limiter, etc. Recently, high-capacity conductors made of REBCO CC have been put forward for power applications, for example, Roebel Assembled Coated Conductor, twisted stacked-tape cable and compact conductor on round core cables.In this paper, a design of HTS strand made from REBCO CCs with geometrical symmetric configuration was put forward. It mainly consists of three parts, that is, the superconducting part, the filling material part and the copper sheath part. The structural feature and potential application of the HTS strand are introduced. The sample of HTS strand was fabricated and the process is described in detail.The model of HTS strand is established using the magnetic field simulation software Ansoft Maxwell according to the actual sizes, so magnetic field distribution on the cross-section of the strand was obtained. The data fitting and interpolation method were proposed according to the magnetic field distribution simulated by finite element method (FEM) to calculate the critical current of the strand. Based on calculating method of critical current in self field, the critical currents of isotropic HTS strand in external field are simulated. Magnetic field dependence of normalized critical current on its orientation as well as angle dependence of normalized critical current on magnetic field are found, respectively. The critical current experiment was carried on in self field and external field at 77 K temperature, respectively. The experimental results show the validity of the simulation model and the calculation method.The AC loss is an important factor for the design of any electrical application and thus determines the capacity of the corresponding cooling system and operation efficiency. The hysteresis loss, eddy current loss and coupling loss of the strand were theoretically discussed, respectively. Based on the analysis and simulation of magnetic field distributions of the strand by FEM, different models were used to calculate the different loss of the strands. The AC loss measurement platform is set up and the AC losses of the strand was also measured at 77K with the conventional electric method and compared with the calculated results.