Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation
| Autor: | Yoshinori Yanagisawa, R. Hu, Masato Takahashi, Tomoaki Takao, D. Uglietti, Hideki Nakagome, Tsukasa Kiyoshi, T. Takematsu, Hideaki Maeda |
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| Rok vydání: | 2010 |
| Předmět: |
Materials science
High-temperature superconductivity Delamination Energy Engineering and Power Technology Epoxy Condensed Matter Physics Electronic Optical and Magnetic Materials Conductor law.invention Electromagnetic coil law visual_art Ultimate tensile strength visual_art.visual_art_medium Electrical and Electronic Engineering Composite material Electrical conductor Radial stress |
| Zdroj: | Physica C: Superconductivity and its Applications. 470:674-677 |
| ISSN: | 0921-4534 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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