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Description
This paper proposes a heretofore unestablished process to calculate the operating current of a ReBCO coil based on the electrical stability of smart insulation (SI) ReBCO coil. The nonhomogeneity of the critical current (IC) of the ReBCO coated conductor (RCC) makes the calculation of the coil IC from the IC-B-T data of a short sample difficult. In addition, at the determining the operating current, even if the coil IC is measured, due to factors such as load conditions, magnetic field, and cooling, a margin of error is given without any clear criteria. The SI ReBCO coil uses a V2O3 material with metal–insulator transition (MIT) characteristics instead of the polyimide film, which is used as a conventional insulating material. A material with MIT characteristics transitions to an insulator below a certain temperature and to a conductor above a certain temperature. The V2O3 material has a transition temperature of approximately 150 K. For the SI ReBCO coil in liquid nitrogen, in a steady state, controllability is ensured by the operation of the insulation coil. Conversely, in the transient state, electrical stability is ensured by the operation of the no-insulation coil for which turn-to-turn current bypass occurs. Accordingly, we propose a process for calculating the operating current based on the characteristics of the SI ReBCO coil. It can address the problem of permanent burnout due to the RCC nonhomogeneity and transient state instability of the conventional ReBCO coil. The proposed process to calculate operating current was verified based on experimental and simulation data of SI ReBCO coils of various specifications.
This research was supported by Korea Electrotechnology Research Institute (KERI) Primary research program through the National Re-search Council of Science & Technology (NST) funded by the Ministry of Science, ICT and Future Planning (MSIP) (No. 19-12-N0101-50).
