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Ansan, South Korea

Kang M.,Soonchunhyang University | Ku M.,Soonchunhyang University | Cha G.,Soonchunhyang University | Lim H.,Iljin Electrical Co.
Progress in Superconductivity and Cryogenics (PSAC) | Year: 2015

The properties of High Temperature Superconducting (HTS) tapes are progressing, as HTS tapes evolve from 1st generation to 2nd generation. This paper presents design and construction of a 2nd generation HTS magnet consisting of two nested GdBCO and YBCO pancake coils. Two HTS tapes of different widths were used to wind the HTS nested magnet. Considering that a higher magnetic field is applied to the inner magnet than to the outer magnet, 12 mm GdBCO tape was used for winding the inner magnet, which consisted of four single pancake windings. Eight double pancake windings wound with 4.4 mm YBCO tapes were used for the outer magnet. The test results show that the central magnetic field of the HTS nested magnet was 920 mT. The measured critical currents of the inner and outer magnet at 77K were 80.8 A and 32.6 A, respectively. © 2015, Korea Institute of Applied Superconductivity and Cryogenics. All rights reserved.

Chae J.E.,National NanoFab Center | Chae J.E.,Chungnam National University | Yang J.-M.,National NanoFab Center | Park K.J.,National NanoFab Center | And 5 more authors.
Journal of Korean Institute of Metals and Materials | Year: 2013

For improving anode materials in Li-ion batteries, the Si system has been noted by many researchers because it has higher energy density and capacity than the graphite anode material used currently. However, the life cycle of the Si anode tends to decrease due to the remarkable volume expansion which is caused by insertion of Li ions when the cell is charged. In this study, we controlled the size of active Si particles, which are dispersed in the inactive matrix, down to several tens of nm as active materials by adding heterogeneous elements. To understand the reaction mechanism of active Si dispersed in the inactive matrix, we analyzed the microstructure of the Si-Ti-Fe alloy using high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The volume expansion behavior was improved by employing the TiFeSi2 matrix and refining the active Si particle size, and life performance of the Li-ion batteries was enhanced. Copyright © The Korean Institute of Metals and Materials.

Yu H.-J.,Chungnam National University | Hong K.-P.,Chungnam National University | Sung M.-S.,Iljin Electrical Co. | Lee S.,Korea Atomic Energy Research Institute | And 2 more authors.
ECS Electrochemistry Letters | Year: 2013

Silicon-Silicide, Si-TiFeSi2, nanocompositewas prepared using amelt-spinning method. Powder neutron diffraction showed a mixing ratio of 38.7(5):61.3(8) and average crystallite sizes of 23.34(3) and 40.60(1) nm for silicon and TiFeSi2, respectively. A conchoidal fracture of the Zangboite-structure TiFeSi2 matrix was observed through microscopy. Electrochemical tests show characteristic features such as rapid stabilization of the first charging profile to about 50 mV and high cyclic performance. The OCP (Open Circuit Potential) measurement and ex-situ XRD represent the Li15Si4 as the final phase. In-situ measurements of the electrode thickness showed improvements of the magnitude and hysteresis of dilation. © 2012 The Electrochemical Society.

Kim J.-H.,Inha University | Ahn H.-J.,Iljin Electrical Co. | Kim K.-Y.,Inha University
Science China Technological Sciences | Year: 2010

High-efficiency design of a mixed-flow pump has been carried out based on numerical analysis of a three-dimensional viscous flow. For analysis, the Reynolds-averaged Navier-Stokes equations with a shear stress transport turbulence model were discretized by finite-volume approximations. Structured grid system was constructed in the computational domain, which has O-type grids near the blade surfaces and H/J-type grids in other regions. The numerical results were validated with experimental data for the heads and hydraulic efficiencies at different flow coefficients. The hydraulic efficiency at the design flow coefficient was evaluated with variation of the geometric variables, i.e., the area of the discharge and length of the vane in the diffuser. The result has shown that the hydraulic efficiency of a mixed-flow pump at the design condition is improved by the modification of the geometry. © 2010 Science in China Press and Springer Berlin Heidelberg.

Kweon D.,Korea Electric Power Research Institute | Koo K.,Korea Electric Power Research Institute | Woo J.,Korea Electric Power Research Institute | Kim Y.,Iljin Electrical Co.
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2012

This paper deals with the hot spot temperature of a transformer when filled with mineral oil, and later on, with natural ester fluid. 14 optical fiber sensors were installed in the 154 kV, 15 MVA transformer filled with mineral oil, with the hot spot temperature measured during the heat run tests. The transformer was retrofilled with natural ester fluid, after which the hot spot temperatures were measured again. For the rated power, the hottest spot temperature was 105.9 °C when the transformer was filled with mineral oil and 129.4 °C when it was filled with natural ester fluid. The hot spot temperature increased by 23.5 °C in the transformer filled with natural ester fluid. This paper applies the hot spot temperature measured using optical fiber sensors to the life curve in natural ester by McShane et al. The life curve of the thermally upgraded kraft paper in natural ester fluid was compared with that in mineral oil, as suggested by the IEEE guide. The life of the transformer filled with natural ester fluid was similar to that filled with mineral oil. Therefore, transformers filled with natural ester fluid do not require increase of cooling pump capacity and surface area of the radiator or reduction of the load to obtain the same life as that of the mineral oil. © 2012 IEEE.

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