Faculty Profiles - KIM Seokbeom

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Superconducting Coil Protection System by Active Power Method

TAKEUCHI K., TSUMIYAMA Y., NANATO N., KIM S. B., MURASE S.

75 253 - 253 2006.11

The shape dependences of HTS bulk and electromagnet on operating characteristics of 3-D superconducting actuator

INOUE T., KIM S. B., SHIMIZU A., MURASE S.

75 160 - 160 2006.11

Investigation of separation phenomenon for ultra-fine particle by magnetic chromatography method (part1)

NAKADA Chiaki, KIM SeokBeom, MURASE Satoru, OKADA Hidehiko

75 268 - 268 2006.11

Three-directional FEM analyses of pre-bending effects for Nb_3Sn composite wires

OKADA I., MURASE S., KIM S. B., NANATO N., AWAJI S., OGURO H., NISIJIMA G., WATANABE K., WAKE M.

75 266 - 266 2006.11

The electromagnet design for 3-D superconducting actuator using HTS bulk

S. B. Kim, T. Inoue, A. Shimizu, S. Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 445 1119 - 1122 2006.10

Language：English Publisher：ELSEVIER SCIENCE BV

We have been developing a three-dimensional (3-D) superconducting actuator consists of a field-cooled HTS bulk for mover and two-dimensional arranged multiple electromagnets as a stator. The HTS bulk is magnetically connected with electromagnets and it can be moved in 3-D directions and rotates without upper side electromagnets and spatial restrictions. The current and the polarity of each electromagnet were individually controlled by the switching power supply. In this paper, we experimentally investigated the effects of the shapes of HTS bulks (disk shape with/without inner hole) and electromagnets (4 and 8 polarities) in points of stabilities and forces of levitation. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2006.06.026

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Current density distributions of the meander type resistive fault current limiters

S. B. Kim, J. Watanabe, N. Nanato, S. Murase, O. B. Hyun

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 445 1069 - 1072 2006.10

Language：English Publisher：ELSEVIER SCIENCE BV

We have been developing a magnetic field measurement system with two-axis hall-probes to study the critical current density distribution or magnetic properties of high-T-c superconductors. In this study, the current distributions at corners of the meander type resistive fault current limiters were measured by hall probe with high spatial resolution. The both of axial and radial magnetic field components (B-x and B-z) according to the direct (DC) and alternating (AC) transport currents were measured by hall probe to estimate the current density distribution with high accuracy. And, it is confirmed that the measured radial components are very useful to estimate the current distribution. (c) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2006.06.027

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Simple measurement of the AC transport current loss for HTS conductors using an active power detection method

N. Nanato, T. Ohzawa, S. Murase, S. B. Kim

CRYOGENICS 46 ( 9 ) 672 - 675 2006.9

Language：English Publisher：ELSEVIER SCI LTD

Reducing AC loss in a superconducting apparatus is one of the most important issues, and the precise measurement and estimation of AC losses are essential to reduce them. The four-terminal method is universally used as an electric measurement method of AC losses for superconducting tapes and wires. In this method, noise and inductive voltage superposed on the terminal voltage of the superconductor are eliminated by a lock-in amplifier and cancel coil, respectively, and then measurement of very small resistive voltage is achieved. However, using this conventional method, a plurality of measuring instruments and apparatuses are needed, and therefore the measuring system becomes complicated and much time is consumed in the calibration process. In this paper, we present a simple and precise measurement system based on an active power detection method, which is proposed as a quench detection method. The proposed system consists of a small number of instruments and apparatus and is less susceptible to noise. Its usefulness is verified by comparing the proposed method and the conventional four-terminal method in measuring the AC transport current loss of a Bi2223/Ag tape. (C) 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.cryogenics.2006.04.001

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Effects of thermal hysteresis on residual resistance ratio of the Cu-stabilized Nb_3Sn superconducting wire

MURASE Satoru, KIYAMA Kazuyuki, OKADA Issei, NANATO Nozomu, KIM SeokBeom

2006 ( 16 ) 1 - 4 2006.6

Characteristics measurements of HTS tape with parallel HTS tapes

Jin-Hong Joo, Seog-Whan Kim, Kyu Jeong Song, Chan Park, Rock-Kil Ko, Ho-Sup Kim, Jung-Pyo Hong, SeokBeom Kim

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 16 ( 2 ) 119 - 122 2006.6

Language：English Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Many high temperature superconducting (HTS) tape manufactures make an effort to reduce the transport current loss of HTS tapes. The knowledge of critical current and self-field in an HTS tape is very useful to compute the transport current losses. The spatial distribution and magnitude of self-field are variable due to the neighboring materials. In this paper, the critical currents and the transport current losses of BSCCO and YBCO tapes with paralleled magnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) are experimentally investigated to improve the AC loss properties. The critical currents of HTS tapes with paralleled Ni tape are slightly decreased and the transport current losses are markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape have not current carrying are more improved than single HTS tape.

DOI： 10.1109/TASC.2005.869674

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Self-field loss in AC transport current of Ni-sheathed MgB2 superconducting tapes

Satoru Murase, Toshiaki Ohzawa, Takashi Harada, Nozomu Nanato, Seok Beom Kim, Yutaka Yamada, Kyoji Tachikawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 16 ( 2 ) 1403 - 1406 2006.6

Language：English Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

AC transport current loss (self field loss) of ex-situ-processed MgB2 superconducting tapes with Ni sheath was measured under different conditions of transport current value, transport current frequency, and temperature. Experimental results were compared with Norris' theoretical curves and previous measured losses of MgB2 tapes with CuNi and stainless-steel sheaths, which were larger than the theoretical ones and previous data. The loss vs. normalized transport current (transport current normalized by critical current) curves varied with temperature and the loss at 9 K was larger than that at 14 K. The measured loss approached Norris' curves in the high normalized transport current region. In order to gain insight into these origins, FEM analysis of magnetic flux concentration by Ni and estimations of hysteresis loss of ferromagnetic nickel-sheath and of homogeneity of the core were carried out. As a result, the hysteresis loss of Ni was very small based on the estimation and the loss, measurement of Ni. Main contributions to large loss are considered to be self-field enhancement due to magnetic flux concentration by the Ni-sheath and critical current density distribution of the MgB2 core caused by the inhomogeneity of critical current density and critical temperature.

DOI： 10.1109/TASC.2006.870448

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Thermal stability of copper ion-plating outer-stabilized Nb_3Al superconducting wire made by the transformation process in the cryocooler cooling

SHIMOYAMA M., MITSUHASHI T., KIYAMA K., MURASE S., KIM S. B., NANATO N., NISHIJIMA G., WATANABE K., KIKUCHI A., TAKEUCHI T.

74 228 - 228 2006.5

Numerical analysis on magnetic chromatography for ultrafine particle and ion separation

KIM SeokBeom, NAKADA Chiaki, MURASE Satoru, OKADA Hidehiko

74 35 - 35 2006.5

Transport current characteristics of HTS tape by neighboring magnetic materials (Part3)

HARADA T., JOO J. H., WATANABE J., INOUE T., NANATO N., MURASE S., KIM S. B.

73 144 - 144 2005.11

Developments of two-axis hall sensor and magnetic field visualization system (Part1)

KIM S. B., WATANABE J., NANATO N., MURASE S., KOH K., HOHKAWA K.

73 142 - 142 2005.11

Transport current characteristics of resistive fault current limiters by two-axis magnetic field measurement (part 2)

WATANABE J., NANATO N., MURASE S., HYUN O. B., KIM S. B.

73 143 - 143 2005.11

FEM analysis of prebending effects for bronze-processed Nb_3Sn wires

KIYAMA K., NANATO N., KIM S. B., MURASE S., OGURO H., NISHIJIMA G., AWAJI S., WATANABE K.

73 45 - 45 2005.11

Dependence of J_c estimation on coil form and measuring position in third harmonic voltage method

KIJIMA K., WATANABE J., NANATO N., MURASE S., KIM S. B.

73 92 - 92 2005.11

Linear motion and rotation characteristics of YBCO bulk using exciting coils

S Okamura, A Shimizu, SB Kim, S Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 426 834 - 838 2005.10

Language：English Publisher：ELSEVIER SCIENCE BV

A superconducting actuator with multiple motions is proposed and experimentally investigated for the development of microelectrical machines. The disk-shaped YBCO bulk was located above the electromagnets and cooled down in the field-cooling method, which enabled the flux pinning. The YBCO bulk superconductor was driven in vertical, horizontal and/or self-rotation by PC-controlled coil currents using multiple electromagnets. The most suitable levitation stability was obtained when we used four electromagnets and NNSS trapped field type. It was confirmed that the levitation force and horizontal moving force strongly depended on the coil current and the air gap length, respectively. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2005.03.069

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The three-dimensional motion characteristics of superconducting actuator

SHIMIZU Akihiro, NANATO Nozomu, KIM SeokBeom, MURASE Satoru

2005 ( 22 ) 19 - 24 2005.6

Protection System for Superconducting Coil by Active Power Detection Method

TSUMIYAMA Yasukazu, FUJIWARA Kenji, NIWA Shinjiro, NANATO Nozomu, KIM SeokBeom, MURASE Satoru

2005 ( 22 ) 81 - 84 2005.6

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