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Park, Heui Joo,Kim, Yeong-chun,Moon, Heejong,Park, Minwon,Yu, Inkeun The Korean Institute of Electrical Engineers 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
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.
Heui Joo Park,Yeong-chun Kim,Heejong Moon,Minwon Park,Inkeun Yu 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
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 (Al2O3) 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 MWclass 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.
Thermal Quench in HTS Double Pancake Race Track Coil
Jae-deuk Lee,Young-kil Kwon,Seung-kyu Baik,Eon-yong Lee,Young-chun Kim,Tae-sun Moon,Heui-ju Park,Woon-sik Kwon,Jung-pyo Hong,Minwon Park,Inkeun Yu,Young-sik Jo Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>In large scale applications, such as SMES, motors and generators, High Temperature Superconducting (HTS) magnets are constructed with many stacks of the double-pancake coils connected in series. In spite of its higher thermal stability, HTS magnet can experience a severe quench, which can resulted from a very small portion. From HTS magnet design point of view, it is very important to predict the possibility of occurrence quench in the designed magnet to provide a suitable quench protection device. In this paper a highly instrumented HTS race track double-pancake coil was prepared to examine the quench development characteristics. It is wound using the Bi-2223 tape. Many voltage taps, cryogenic thermocouples and heater were installed in the winding. Conduction cooling method is adapted for the convenience of temperature. Quench development in the coil was measured under different operating current. The experimental details and results are presented in this paper.</P>