• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.42-46
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• 2002

This research is conducted with the object of Piling up the foundation of design technologies for high temperature superconducting (HTS) power transformer which is thought to be as a powerful power transformer of next generation. In this study, not only the theoretical design of high temperature superconducting (HTS) transformer but also the arrangements of superconducting tape and the cooling method have been conducted. Moreover, electromagnetic analyses using finite element method (FEM) were conducted to confirm the efficiency of the designed transformer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.787-789
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• 2000

High temperature superconducting YBCO films have been grown on MgO substrates by pulsed laser deposition (PLD) with Nd:YAG laser Superconducting microwave filter was fabricated by conventional photolithography method. We have designed filter with the center frequency of 14 GHz. We have measured the center frequency of filter at 77 K and its critical temperature 89K. Also we have designed another filter to compare frequency responses. The measured frequency responses will be presented.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.7
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• pp.364-369
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• 2002

In this paper, 3-D magnetostatic finite element simulation of a rotux type Low-Tc superconducing (LTS) superconducting power supply, finite element method, cryogenic system, superconducting foil by generated magnetic flux from the rotating pole. The magnetic flux density on the superconducting foil caused by two exciters is therefore sufficiently greater than its critical magnetic flux density and it is an essential point in LTS power supply design. To establish the sufficient flux path of this machine, ferromagnetic materials is used in this power supply. When ferromagnetic materials is used at extremely low temperature, its characteristic of magnetization differs to that at room temperature. For this reason, special consideration is needed in the magnetic analysis of cryogenic systems. When the excitation current is 10A, the normal spot appears on superconducting foil. The results of this analysis are calculated and compared with the experimental results. The linkage flux due to the excitation current of 10, 20, 30, 40 and 50A are respectively $1.30{\times}10-4$, $2.67{\times}10-4$, $5.08{\times}10-4$ and $6.15{\times}10-4Wb$.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.1
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• pp.15-20
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• 2004

This paper discusses electrical insulation characteristics at cryogenic temperature, especially focusing on partial discharge (PD) inception characteristics, for high temperature superconducting cables. In liquid nitrogen (L$N_2$) / polypropylene (PP) laminated paper composite insulation system, PD inception strength (PDIE) was evaluated in terms of volume effect and V-t characteristics. Different kinds of butt gap condition were applied in the experiments, using parallel plane and coaxial cylindrical cable samples. Experimental results revealed that the volume effect on PDIE could be evaluated by the statistical stressed liquid volume (SSLV) taking account the discharge probability not only in the butt gap but also in the other thin layers between PP laminated papers. Furthermore, the indices n of V-t characteristics at PD inception were estimated to be 80∼110, irrespective of the butt gap condition.

• Progress in Superconductivity
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• v.14 no.2
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• pp.122-127
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• 2012

Current leads are one of the important components for carrying the current to the coil in the superconducting magnet system. Heat leakage through the current lead is the major factor of entire heat load in the cryogenic system because current leads carry the current from room temperature to near 4 K, connecting thermally each other. Therefore, minimization heat load through current lead can reduce the operating temperature of superconducting magnet. The semi-retractable current lead, composed of multi-contact connector and HTS element, is one of good options. Comprehension of Multi-contact connector's structure, contact resistance and heat generation is essential for estimating heat generation in current leads. Multi-contact connector has several louvers inside of socket and the shape, number, size of louvers are different with the size of connector. Therefore contact area, current path and contact resistance are also different. In this study, the contact resistance in multi-contact connector is measured using the electrical power as a function of connector's size and temperature. Also, the unique correlation of electrical contact resistance is derived and heat generation is estimated for superconducting magnet application.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.40-44
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• 2013

The contactless power transfer (CPT) systems have been recently gaining popularity widely since it is an available option to realize the power delivery and storage with connector-free devices across a large air gap. Especially, the CPT with electromagnetic resonance coupling method is possible to exchange energy within 2 m efficiently. However, the power transfer efficiency of CPT in commercialized products has been limited because the impedance matching of coupled coils is sensitive. As a reasonable approach, we combined the CPT system with HTS wire technology and called as, superconducting contactless power transfer (SUCPT) system. Since the superconducting coils have an enough current density, the superconducting antenna and receiver coils at CPT system have a merit to deliver and receive a mass amount of electric energy. In this paper, we present the feasibility of the SUCPT system and examine the transmission properties of SUCPT phenomenon between room temperature and very low temperature at 77 K as long as the receiver is within 1.0 m distance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.69-74
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• 2018

Large industrial motors require a large area because of the high risk of shutdown accidents and large industrial accidents due to the lowering of the dielectric strength of the armature windings and overheating problems. Therefore, there is a demand for a large-capacity motor that has small size, light weight, and excellent dielectric strength compared with conventional motors. Superconducting motors have advantages of high efficiency and output power, low size, low weight, and improved stability. This results from greatly increasing the magnetic field generation by using superconductive field coils in rotating machines such as generators and motors. It is very important to design and analyze the cooling system to lower the critical temperature of the wires to achieve superconducting performance. In this study, a field loss analysis and low-temperature heat transfer analysis of the cooling system were performed through the conceptual design of a 100-HP high-temperature superconducting synchronous motor. The field loss analysis shows that a uniform pore magnetic flux density appears when high-temperature superconducting wire is used. The low-temperature heat transfer analysis for gaseous neon and liquid neon showed that a flow rate of 1 kg/min of liquid neon is suitable for maintaining low-temperature stability of the high-temperature superconducting wire.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.10-13
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• 2015

High-temperature superconducting coated conductors (HTS-CCs) are good candidates for resistive superconducting fault current limiter (RSFCL) applications. However, the high current density they can carry and their low thermal diffusivity expose them to the risk of thermal instability. In order to find the best compromise between stability and cost, it is important to study the heat transfer between HTS-CCs and the liquid nitrogen ($LN_2$) bath. This paper presents an experimental method to monitor in real-time the temperature of a quenched HTS-CC during a current pulse. The current and the associated voltage are measured, giving a precise knowledge of the amount of energy dissipated in the tape. These values are compared with an adiabatic numerical thermal model which takes into account heat capacity temperature dependence of the stabilizer and substrate. The result is a precise estimation of the heat transfer to the liquid nitrogen bath at each time step. Measurements were taken on a bare tape and have been repeated using increasing $Kapton^{(R)}$ insulation layers. The different heat exchange regimes can be clearly identified. This experimental method enables us to characterize the recooling process after a quench. Finally, suggestions are done to reduce the temperature increase of the tape, at a rated current and given limitation time, using different thermal insulation thicknesses.

• Electrical & Electronic Materials
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• v.10 no.6
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• pp.589-607
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• 1997

• 한국초전도학회:학술대회논문집
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• v.15
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• pp.6-6
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• 2005