Studies to clarify methods to reduce AC losses of high temperature superconducting (LHS) wires

在本项目中，我们开展了以下研究，以阐明降低高温超导(LHS)导线交流损耗的方法。1)测量高温超导导线在直流和交流外磁场中的交流损耗。提出了一种测量超导导线在外磁场中交流传输电流损耗的方法，以避免杂散损耗。用该方法测量了Bi2223银套带材、YBCO带材和Bi2212棒等多种高温超导线材的交流输运电流损耗。结果发现，在许多情况下，测量数据与广泛接受的Norris公式计算值之间存在显著差异。很好地与测量结果一致。我们还测量了组装导线中导线的传输电流交流损耗，发现由于测量的导线附近的导线的传输电流产生的磁场降低了交流损耗。这一结果表明，通过合理的导线结构设计可以降低输运电流损耗。2)对低温超导体(LTS)的电磁行为进行建模，计算交流损耗。通过对低温超导体(LTS)的理论模型进行修正，建立了定量计算HIS导线交流损耗的理论模型。研究结果验证了高温超导导线的理论模型。3)提出了设计低交流损耗导线的方法。基于研究2)建立的理论模型，提出了降低交流损耗的方法。用LTS导线和组合导线模拟低损耗结构的导线，验证了方法的有效性，通过以上研究，我们认为项目的目的是很好的。

In this project we performed the following studies to clarify methods to reduce AC losses of high temperature superconducting (LHS) wires.1) Measurement of AC losses of HTS wires in DC and AC external magnetic field.We developed a method to measure AC transport current losses of superconducting wires in the external magnetic field avoiding spurious losses. Using this method, we measured the AC etransport current losses of various HTS wires, such as Bi 2223 silver sheathed tapes, YBCO tapes and Bi22l2 rod. As the results, we found that in many case there were significant discrepancies between the measured data and values calculated from Norris formula which was widely accepted. to well agree with measurement. We also measured the transport current AC loss of a wire in assembled, conductor and found that the AC loss was decreased due to the magnetic field produced by transport currents of wires adjacent to the wire whose loss was measured. This result suggests that the transport current loss can be reduced by proper design of wire structure.2)Modeling the electromagnetic behavior of LTS wire to calculated the AC loss.We made a theoretical model to quantitatively calculate the AC losses of HIS wires by modifying the theoretical model developed for the low temperature superconductor (LTS). The theoretical model for HTS wires was verified by the result of the study 1).3)Proposing methods to design a wire with low AC losses.Based on the theoretical model formulated by the study 2), we proposed methods to reduce the AC losses. Validity of the methods were demonstrated by using LTS wires and assembled conductor simulating a wire with low loss structure.By above studies, we consider the purpose of the project was well fulfilled.