Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation
Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation
复制标题
DOI：
10.1016/j.physc.2010.06.009
复制
发表时间：
2010-09-01
影响因子：
1.7
通讯作者：
Maeda, H.
中科院分区：
文献类型：
--
作者：
Takematsu, T.;Hu, R.;Maeda, H.
现在YBCO涂层导体已经商业化，已经开发了许多YBCO线圈。然而，迄今为止，它们的基本性能尚未得到系统的研究。在这里，我们展示了一个YBCO双饼线圈。环氧树脂浸渍的YBCO双饼线圈的临界电流显著下降，即正常电压出现在8A以上，仅为干线圈的18%。据推断，如果在冷却过程中产生的累积径向应力超过YBCO涂层导体的临界横向应力（通常为10 MPa），则会发生劣化。在这些条件下，导体在缓冲层和YBCO层之间的界面处脱粘，或者在YBCO层本身中断裂，导致YBCO层上的裂纹，导致临界电流的显著下降。如果线圈是干绕的或用石蜡浸渍的，则这些负面影响被抑制，因为匝之间的结合强度可以忽略不计，并且因此如果累积径向应力趋于拉伸，则匝被分离。对于非圆形线圈，环氧树脂浸渍是不可避免的，由于累积拉伸横向应力退化仍然是主要问题。(C)2010爱思唯尔有限公司版权所有。
Now that YBCO-coated conductors have been commercialized, a number of YBCO coils have been developed. However, their basic performances have not been systematically investigated so far. Here, we demonstrate that of a YBCO double pancake coil. The critical current of an epoxy impregnated YBCO double pancake coil was substantially degraded, i.e. the normal voltage appears above 8 A, only 18% of that for the dry coil. It was inferred that degradation occurs if the cumulative radial stress developed during cool down exceeds the critical transverse stress for the YBCO-coated conductor (typically 10 MPa). Under these conditions, the conductor was debonded at the interface between the buffer layer and YBCO layers, or fractured in the YBCO layer itself, causing cracks on the YBCO layer, resulting in a significant decline of the critical current. These negative effects are suppressed if the coils are dry wound or impregnated with paraffin, as the bonding strengths between turns are negligible and therefore turns are separated if the cumulative radial stress tends to be tensile. For non-circular coils in which epoxy impregnation is inevitable, degradation due to cumulative tensile transverse stress is still the major problem. (C) 2010 Elsevier B.V. All rights reserved.