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Fabrication and Evaluation of High-Tc Superconductor Cables Designed by Using the Novel Calculation Method of AC Transport self-field Losses

采用交流传输自场损耗新计算方法设计的高温超导电缆的制作和评估

基本信息

批准号：
12450110
负责人：
0OTA Akio
金额：
$ 9.09万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

1. Reduction in AC transport losses for Ag-sheathed Bi2223 tapes by introduction of resistive barriersWe succeeded in reducing AC transport losses in self-Held at 77 K for the Ag-sheathed Bi2223 tapes, fabricated by a four-roller machine to make a rectangular deformation and also by the introduction of Bi2201 sheets as resistive barriers in an arrangement parallel to the wide surface of tapes. Although the main contribution to the losses comes from the hysteresis loss of the superconductor, the loss value for the tape is reduced by approximately 70% compared with the value for the multifilamentary tapes prepared by a standard powder-in-process without the resistive barriers. However, the critical current densities (J_c) are much lower than that for the standard tape without the resistive barriers because of the some reaction of Bi2201 sheets with Bi2223 filaments during the heat treatments. To solve this problem, we introduced the mixture of Ca_2CuO_3 and 30 wt.% Bi2212 powders as resi … More stive barriers. The Ca_2CuO_3 powder is has little side effect on the J_c values of the Bi2223 tapes. The experimental results indicate that the transport losses were reduced by introduction of the resistive barrier in an arrangement parallel to the wide surface of tapes, while the J_c value was almost not deteriorated compared with the tape without barriers.2. Reduction in AC transport losses for Ag-sheathed Bi2223 tapes by changing the filament arrangementsSignificant reduction in AC transport losses in self-field at 77 K has been achieved to Ag-sheathed Bi2223 multifilamentary tapes, which were fabricated by a rectangular deformation process using a two-axial rolling (TAR). This achievement is not made by the introduction of resistive barriers but the improvements of filament arrangements in the tapes. Despite the main contribution to the losses comes from the hysteresis loss of the superconductor, the transport losses for the tape samples are decreased by 50-70% particularly in high current range near the critical current (I_c) compared with the value for the Bi2223 multifilamentary tapes prepared by standard PIT process. Numerical calculations suggest that the reduction of transport losses mainly ascribed to the division of field-free core with neither currents nor electromagnetic field in the sectioned filament groups near the tape edge under AC current transmission.3. Evaluation of AC transport losses for cable conductors composed of superconductor tape strandsWe investigated the AC transport losses in self-field on cable conductor composed of Ag-sheathed Bi2223 tape strands with different cross sectional geometry. The loss values of the conductors strongly depend on the filament arrangements in the tape strands and the arrangement of tape strands in the conductors. This can be explained the calculation result of current distributions and loss density distributions, varying with the geometrical factor of conductors. We also calculated the inter-layer magnetic flux under the condition of I_o=I_c for the magnetic field distributions in multi-layer cables as a parameter of spiral length. Although the value of inter-layer flux becomes zero in an adjusted spiral length, the flux between tape center and edges shows non-zero values, indicating that the transport losses for the cables with adjusted spiral length are mainly generated in the edge part of tape strands. Therefore, there is much room for further improvement in actual magnetic field structure to suppress the loss generation in the cables. Less

1.采用电阻阻挡层降低Bi_（2223）包银带材的交流输运损耗我们成功地降低了Bi_（2223）包银带材在77 K自保持下的交流输运损耗。虽然主要贡献的损失来自超导体的磁滞损耗，磁带的损失值减少了约70%的值相比，由一个标准的粉末在过程中制备的多芯磁带没有电阻屏障。然而，由于热处理过程中Bi 2223丝与Bi 2201片发生反应，临界电流密度（J_c）远低于无阻障的标准带材。为了解决这一问题，我们引入了Ca_2CuO_3和30 wt.%的混合物Bi 2212粉末作为树脂 ...更多信息静态障碍。Ca_2CuO_3粉末对Bi_（2223）带材的J_c值影响不大。实验结果表明，引入平行于宽表面的阻性阻挡层可以降低传输损耗，而J_c值与未引入阻性阻挡层的情况相比几乎没有恶化.通过改变带材的丝长来降低Ag包覆Bi 2223带材的交流输运损耗通过双轴轧制（TAR）的矩形变形工艺制备的Ag包覆Bi 2223多芯带材，在77 K的自场中实现了交流输运损耗的显著降低。这一成就不是通过引入阻障实现的，而是通过改进带中的细丝排列实现的。尽管超导体的磁滞损耗是损耗的主要贡献，但在临界电流（I_c）附近的大电流范围内，超导带材的输运损耗比标准PIT工艺制备的Bi_（2223）超导带材的输运损耗降低了50-70%。数值计算表明，在交流电流传输下，带边附近的分段丝极组中，无场芯的分割是输运损耗降低的主要原因.本文研究了由不同截面形状的Bi_（2223）超导带束组成的超导电缆导体在自场中的交流输运损耗。导体的损耗值很大程度上取决于带股中的细丝布置和导体中带股的布置。这可以用电流分布和损耗密度分布随导体几何因子变化的计算结果来解释。在I_o=I_c的条件下，以螺旋长度为参数，计算了多层电缆的层间磁通分布。调整螺旋长度后，虽然层间磁通量为零，但胶带中心与边缘之间的磁通量呈现非零值，表明调整螺旋长度后的电缆传输损耗主要发生在胶带股的边缘部分。因此，在实际的磁场结构中存在进一步改进以抑制电缆中损耗产生的很大空间。少