DOI QR코드

DOI QR Code

Improvement of Degradation Characteristics in a Large, Racetrack-shaped 2G HTS Coil for MW-class Rotating Machines

  • Park, Heui Joo ;
  • Kim, Yeong-chun ;
  • Moon, Heejong ;
  • Park, Minwon ;
  • Yu, Inkeun
  • Received : 2017.10.19
  • Accepted : 2017.12.12
  • Published : 2018.05.01

Abstract

Degradation due to delamination occurs frequently in the high temperature superconductors (HTS) coil of rotating machines made with 2nd generation (2G) HTS wire, and the authors have observed other similar cases. Since an HTS field coil for a rotating machine is required to have stable current control and maintain a steady state, co-winding techniques for insulation material and epoxy resin for shape retention and heat transfer improvement are applied during coil fabrication. However, the most important limiting factor of this technique is delamination, which is known to be caused by the difference in thermal expansion between the epoxy resin and 2G HTS wire. Therefore, in this study, the experimental results of mixing the ratio of epoxy resin and alumina ($Al_2O3$) filler were applied to the fabrication of small and large test coils to solve the problem of degradation. For the verification of this scheme, eight prototypes of single pancake coils with different shapes were fabricated. They showed good results. The energization and operation maintenance tests of the stacked coils were carried out under liquid neon conditions similar to the operation temperature of an MW-class rotating machine. In conclusion, it was confirmed that the alumina powder mixed with epoxy resin in an appropriate ratio is an effective solution of de-lamination problem of 2G HTS coil.

Keywords

2G HTS coil;Degradation;Delamination;Insulation material;Epoxy resin;Filler;Coefficient of thermal expansion

References

  1. J. Lloberas, A. Sumper, M. Sanmarti, X. Granados, "A review of high temperature superconductors for offshore wind power synchronous generators," Renewable and Sustainable Energy Reviews, vol. 38, pp. 404-414, 2014. https://doi.org/10.1016/j.rser.2014.05.003
  2. C. Barth, N. Bagrets, K-P. Weiss, C. M. Bayer and T. Bast, "Degradation free epoxy impregnation of REBCO coils and cables," Superconductor Science and Technology, vol. 26, no. 5, 2013.
  3. M. Oomen, W. Herkert, D. Bayer, P. Kummeth, T. Arndt, "Manufacturing and test of 2G-HTS coils for rotating machines: Challenges, conductor requirements, realization," Physica C: Superconductivity and Its Applications, vol. 482, pp.111-118, 2012. https://doi.org/10.1016/j.physc.2012.04.021
  4. Y. Zhang, D.W. Hazelton, A.R. Knoll, J.M. Duval, P. Brownsey, S. Repnoy, S. Soloveichik, A. Sundaram, R.B. McClure, G. Majkic, V. Selvamanickam, "Adhesion strength study of IBAD-MOCVD-based 2G HTS wire using a peel test," Physica C, vol. 473, pp. 41-47, 2012. https://doi.org/10.1016/j.physc.2011.11.013
  5. T. Takematsu, R. Hu, T. Takao, Y. Yanagisawa, H. Nakagome, D. Uglietti, T. Kiyoshi, M. Takahashi, H. Maeda, "Degradation of the performance of a YBCO-coated conductor double pancake coil due to epoxy impregnation," Physica C, vol. 470, pp. 674-677, 2010. https://doi.org/10.1016/j.physc.2010.06.009
  6. Y. Zhang, D.W. Hazelton, A.R. Knoll, J.M. Duval, V. Selvamanickam, "Adhesion strength study of IBAD-MOCVD-based 2G HTS wire using a peel test," Physica C: Superconductivity, vol. 473, pp. 41-47, 2012. https://doi.org/10.1016/j.physc.2011.11.013
  7. A. Gorospe, A. Nisay, J.R. Dizon, H.S. Shin, "Delamination behaviour of GdBCO coated conductor tapes under transverse tension," Physica C: Superconductivity, vol. 494, pp. 163-167, 2013. https://doi.org/10.1016/j.physc.2013.04.062
  8. H.S. Shin and M.J. Dedicatoria, "Variation of the strain effect on the critical current due to external lamination in REBCO coated conductors," Superconductor Science and Technology, vol. 25, no. 5, p. 054013, 2012.
  9. H. Park, A. Kim, S. Kim, M. Park, K. Kim, T. Park, "Mechanical and electric characteristics of vacuum impregnated no-insulation HTS coil," Physica C, vol. 504, pp.138-143, 2014. https://doi.org/10.1016/j.physc.2014.04.010
  10. Y. Yanagisawa, K. Sato, T. Matsuda, T. Nagato, H. Kamibayashi, H. Nakagome, X. Jin, M. Takahashi, H. Maeda, "An ultra-thin polyimide insulation coating on REBCO conductors by electrodeposition produces a maximum overall current density for REBCO coils," Physica C: Superconductivity, vol. 495, pp. 15-18, 2013. https://doi.org/10.1016/j.physc.2013.07.009
  11. M. Yoshizumi, N. Sakai, T. Izumi, "Improvement of delamination strength of REBCO coated conductors," Physics Procedia, vol. 58, pp. 150-153, 2014. https://doi.org/10.1016/j.phpro.2014.09.029
  12. S.H. Jeong, J.B. Song, Y.H. Choi, S.G. Kim, B.S. Go, M. Park, H. Lee, "Effect of micro-ceramic fillers in epoxy composites on thermal and electrical stabilities of GdBCO coils," Composites: Part B, vol. 94, pp. 190-196, 2016. https://doi.org/10.1016/j.compositesb.2016.03.065
  13. L. Ren, K. Pashayi, H.R. Fard, S.P. Kotha, T. Borca-Tasciuc, R. Ozisik, "Engineering the coefficient of thermal expansion and thermal conductivity of polymers filled with high aspect ratio silica nanofibers," Composites: Part B, vol. 58, pp. 228-234, 2014. https://doi.org/10.1016/j.compositesb.2013.10.049
  14. Marlon J. Dedicatoria, John Ryan C. Dizon, Hyung-Seop Shin and Ki-Duk Sim, "Establishment of CTE Measurement Procedure for PPLP at 77K HTS Power Cables using Double Extensometers," Superconductivity and Cryogenics, vol. 14, no. 4, pp. 24-27, 2012.
  15. A.R. Nisay and H.S. Shin, "Mechanical and electro-mechanical analysis in differently stabilized GdBCO coated conductor tapes with stainless steel substrate," Progress in Superconductivity and Cryogenics, vol. 15, no. 2, pp. 29-33, 2013.