Faculty Profiles - KIM Seokbeom

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Fundamental studies for the application of quench protection systems based on an active power method for cryocooled LTS coils

Kazuya Takeuchi, Nozomu Nanato, Satoru Murase, SeokBeom Kim, Gen Nishijima, Kazuo Watanabe, Takao Takeuchi, Nobuya Banno, Akihiro Kikuchi

CRYOGENICS 48 ( 3-4 ) 148 - 153 2008.3

Language：English Publisher：ELSEVIER SCI LTD

When the quenching occurs in a superconducting coil, excessive joule heating in normal area may damage the coil. It is necessary to detect quenching in the coil as soon as possible and discharge the magnetic energy stored in the coil. Therefore, we propose a superconducting coil protection system based on an active power method. The system is highly resistant to the noise and does not require cancel voltage taps, so it is useful for both AC and DC coils. We have presented the effectiveness of the system using some test coils cooled in LN2 or LHe. However, we have not discussed the effectiveness of the proposed system for helium-free cryocooled magnets, in which a larger temperature rise occurs after quenching than in liquid-cooled magnets. In this paper, we verify the effectiveness and practicality of the proposed system through coil protection tests for a cryocooled Nb3Al LTS coil. (C) 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.cryogenics.2008.02.002

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Development of superconducting actuator for the contactless transporter

SeokBeom Kim, K. Kawakami, M. Nishimoto, Y. Okimoto, T.Nakano, S. Murase

International Conference on Electrical Machines and Systems (ICEMS2007) 1719 - 1722 2008

Superconducting Coil Protection System by Active Power Method : Characteristic Improvement by Canceling Mutual Inductive Voltage

TAKEUCHI K., INOUE T., NANATO N., KIM S. B., MURASE S.

77 88 - 88 2007.11

Thermal stability in the cryocooler cooling for RHQT processed Nb_3Al superconducting wires

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

77 40 - 40 2007.11

The defect detection in HTS films on third-harmonic voltage method using various inductive coils

S. B. Kim

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 463 702 - 706 2007.10

Language：English Publisher：ELSEVIER SCIENCE BV

We purposed and tested the contactless ac inductive method to estimate the critical current density of high temperature superconducting (HTS) films by detecting a third-harmonic voltage. In this study, a minimum diameter of the HTS film to estimate the correct critical current density was experimentally investigated using three miniature inductive coils with various sizes. It was clarified that the correct critical current density could be measured and estimated when the diameter of HTS films was about 1.2 times larger than outer diameter of each tested inductive coil. The accuracy of detection for micro-scale defects with various shapes in HTS films was studied using miniature inductive coils by the third-harmonic voltage method. And it was possible to detect the defects in HTS films by obtained the slope values of initial region at generated third-harmonic voltage traces. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.03.481

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Cap core design for high levitation force in a 3D superconducting actuator with HTS bulk

J. H. Joo, S. B. Kim, T. Inoue, A. Shimizu, S. Murase

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 463 420 - 425 2007.10

Language：English Publisher：ELSEVIER SCIENCE BV

We have been developing a 3D superconducting actuator with HTS (high temperature superconducting) bulk and two-dimensionally arranged multiple electromagnets. The application of HTS bulk enables stable levitation and suspension due to its strong pinning force. The performance of the actuator is determined mainly by the spatial distribution of the generated magnetic field of the electromagnets. For the sake of improving the levitation force, we proposed to attach a sliced iron sheet (we called this cap core) on the top surface of the core in each electromagnet. The proposed cap core was expected to lead to an intensive concentration and abrupt gradient increase of the perpendicular component in the magnetic field through the HTS bulk of the electromagnets. We experimentally confirmed and measured the effect of the cap core. For the optimized design of the cap core, we calculated the spatial distribution of the magnetic field on the surface of the electromagnet using 3D FEM analysis for several cap cores and estimated the levitation force of the HTS bulk using the calculated result. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.05.029

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Development of 3-D superconducting actuator using HTS bulks based on eight-poles electromagnets

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

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 463 1346 - 1351 2007.10

Language：English Publisher：ELSEVIER SCIENCE BV

We have been developing a three-dimensional (3-D) superconducting actuator with HTS bulk and electromagnets. Proposed 3-D superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. To realize the 3-D superconducting actuator with high performance, we have to investigate the shape-dependences of electromagnets and HTS bulk on levitating characteristics. In this study, we fabricated the individually controlled eight-polarities electromagnets and the two kinds of bolted joints cap cores to improve the control ability and levitation characteristics. And also, we prepared the disk-shaped and ring-shaped (with 20 rum inner diameter) HTS bulk with 60 mm diameter, and evaluated how magnetic field distribution influences the levitating characteristics as functions of levitation force and height. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.03.496

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The self-field loss on AC transport current for in situ PIT processed MgB2 superconducting tapes with carbides addition and the carbon steel sheath

T. Ohzawa, N. Nanato, S. B. Kim, S. Murase, D. Miyagi, N. Takahashi, Y. Yamada, A. Nitta, K. Tachikawa

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 463 798 - 801 2007.10

Language：English Publisher：ELSEVIER SCIENCE BV

The new in situ MgB2 tapes with/without SiC addition and the hot pressing process have been fabricated using the carbon steel sheath. The critical temperature (T-c), critical current density (J(c)) and the AC transport current loss of those tapes have been studied and discussed in various conditions. The MgB2 tapes with the carbon steel sheath that improved the core hardness and homogeneity, resulting in high J(c), and the SiC addition, and the hot pressing brought narrow T-c transition width. As the carbon steel has ferromagnetism, it affected the loss of the MgB2 tape. The large losses that were two to three orders of magnitude higher than Norris' theoretical curve were obtained. It was clarified that the main loss of the MgB2 tape was the hysteresis loss of the carbon steel sheath. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.04.266

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Development of quench protection system for HTS coils by active power method

N. Nanato, Y. Tsumiyama, S. B. Kim, S. Murase, K.-C. Seong, H. J. Kim

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 463 1281 - 1284 2007.10

Language：English Publisher：ELSEVIER SCIENCE BV

Recently, HTS coils have been developed for electric power apparatuses. In superconducting coils, local and excessive joule heating may give damage to the superconducting windings when a quench occurs and therefore it is essential that the quench is detected quickly and precisely so that the coils can be safely discharged. Resistive voltage measurement method is universally used for the quench detection, however, it is vulnerable to an electromagnetic noise which causes insufficient quench detection and at least needs a central voltage tap in windings. In a large superconducting coil, a lead-wire from the central voltage tap may cause a short-circuit when high voltage will be applied. In this paper, we present a quench protection system based on the active power method which detects a quench by measuring the instantaneous active power generated in a superconducting coil. The protection system based on this method is very strong against to the noise and no more needs a central voltage tap. The performance of system developed by us is confirmed by using test coil wound with Bi-2223 HTS tapes. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.02.047

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Development of magnetic chromatograph system for magnetic particle and ion separation with superconducting magnet

S. B. Kim, C. Nakada, S. Murase, H. Okada, T. Ohara

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 463 1306 - 1310 2007.10

Language：English Publisher：ELSEVIER SCIENCE BV

The magnetic chromatograph (MC) system is one of the promising methods for ion separation because of its strong magnetic field gradients. We have been developing the MC system to separate the fine particles and ions, and have also developed the numerical analysis computer code based on fluid dynamics and electromagnetism to investigate the separating characteristics and optimization of MC system. We investigated MC technology for magnetic particles separation using superconducting magnet and micro-scale magnetic column with ferromagnetic wires experimentally. A channel height of magnetic column for ion separation was optimized by the developed computer code. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2007.04.305

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Fabrication and application of two-axis hall sensor array using ELO film bonding technology

Keishin Koh, Seok Beom Kim, Koji Hohkawa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 ( 2 ) 3773 - 3776 2007.6

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

In this paper, we report a basic study on the development of a two-axis Hall sensor array using epitaxial lift-off (ELO) film bonding technology. We developed a novel Hall sensor array fabricated on a Si substrate that can directly measure axial and radial magnetic field components (Bx and Bz) simultaneously. We investigated conditions of basic fabrication process and fabricated a basic test device. We also estimated basic characteristics of the Hall sensor and measured the DC self-magnetic field profiles of a YBCO strip. The results clarified that the ELO film bonding technology is suitable for fabricating two-axis Hall sensor array.

DOI： 10.1109/TASC.2007.899041

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Three-directional FEM analyses of pre-bending effects for Nb3Sn composite wires

Satoru Murase, I. Okada, K. Kiyama, N. Nanato, S. B. Kim, H. Oguro, G. Nishijima, S. Awaji, K. Watanabe, M. Wake

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 ( 2 ) 2676 - 2679 2007.6

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

Pre-bending effects of Nb3Sn composite wires, enhancement in J(c) at the as-cooled condition and J(c) peak, J(cm), against applied tensile strain, are well known in especially Cu-Nb reinforced Cu stabilized Nb3Sn wire. In an attempt to understand the effects, three directional strain analyses using FEM were studied by considering thermally-induced residual strain due to temperature difference between the reaction temperature and the cryogenic temperatures including the pre-bending process at room temperature for three types of Nb3Sn composite wires. To evaluate effects of change in three directional strain, the von Mises strain was introduced. As a result, the minimum von Mises strain against the applied tensile strain corresponded to J(cm); low strain shows J(cm) enhancement by the pre-bending for Cu-Nb reinforced Nb3Sn wire. It was found that there is a direct correlation between the minimum von Mises strain and J(cm) related to the pre-bending.

DOI： 10.1109/TASC.2007.899597

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Characteristics of a 3-D HTS actuator with various shaped electromagnets

S. B. Kim, T. Inoue, A. Shimizu, J. H. Joo, S. Murase

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 17 ( 2 ) 2327 - 2330 2007.6

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

We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and move in free space. Proposed superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. The 2-D arranged electromagnets were individually controlled to move the HTS bulk. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in clean rooms where silicon wafers are manufactured. Wafers must be protected from contact with dust and other contamination. To realize the superconducting actuator with HTS bulks, the electromagnetic characteristics of HTS bulk, such as trapped field strength and patterns, should be clarified and the optimized controlling system is also required. Therefore, in this study, to construct the optimal 3-D actuator system, the fundamental characteristics of the levitation for HTS bulks with individually controlled four and eight-polarities electromagnets were investigated experimentally. And two kinds of cap cores attached the top of the core to improve the control ability of proposed actuator were fabricated and tested.

DOI： 10.1109/TASC.2007.898974

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Investigation of separation phenomenon for ultra-fine particle by magnetic chromatography method (part 2)

OKIMOTO Yuichi, KIM SeokBeom, MURASE Satoru, OKADA Hidehiko

76 88 - 88 2007.5

Effects of SiC addition on temperature and magnetic-field dependences of flux pinning in MgB_2 tapes

KUWASHIMA H., KIM S. B., NANATO N., MURASE S., YAMADA Y., NITTA A., TACHIKAWA K.

76 36 - 36 2007.5

Characteristics of a 3-D HTS actuator with various shaped electromagnets

KAWAKAMI Kouhei, KIM SeokBeom, NAKANO Toshiya, MURASE Satoru

76 83 - 83 2007.5

Design of electromagnet for high levitation force in 3D superconducting actuator

Jin-Hong Joo, SeokBeom Kim, Kei Hitomi, Satoru Murase

Proceeding of International Conference on Electrical Machines and Systems, ICEMS 2007 1549 - 1552 2007

Language：English

We have been developing a new type of 3-D superconducting actuator using the strong pinning force of HTS (High Temperature Superconducting) bulk. The system includes HTS bulk and two-dimensionally arranged multiple electromagnets. The application of HTS bulk enables stable levitation and suspension, and its performance is determined mainly by the spatial distribution of the generated magnetic field of the electromagnets. To enhance the levitation force in the actuator, it is necessary to design the optimized geometry of the electromagnets. The target of the design is to lead to an intensive concentration and abrupt gradient increase of the perpendicular component in the magnetic field through the HTS bulk over the electromagnets. For the optimized design of the electromagnets, we calculated the spatial distribution of the trapped magnetic field and the levitation force of the HTS bulk using 3-D FEM analysis that is adopted the critical state model.

DOI： 10.1109/ICEMS.2007.4412287

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The transport characteristics and the self-field distribution for high-Tc superconductor with neighboring magnetic materials

Jin-Hong Joo, Seok-Beom Kim, Satoru Murase

IEEJ Transactions on Power and Energy 127 ( 1 ) 327 - 334 2007

Language：Japanese

Many high-Tc superconducting (HTS) tape manufactures make an effort to improve the transport characteristics of HTS tapes. When AC or DC current flows in the HTS tape, AC or DC magnetic self-fields are induced around the conductor by the current and these self-fields affect on the AC loss and the critical current like the transport characteristics of HTS tapes. The spatial distribution and magnitude of the self-field are variable due to the neighboring materials on the HTS tape. In this paper, the relation between the transport characteristics and the self-field distribution of HTS tapes with paralleled ferromagnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) is experimentally investigated. The self-fields according to the DC and AC transport currents were measured by hall probe with axial and radial magnetic field components. The critical currents of HTS tapes with paralleled the Ni tape are slightly decreased and the transport current losses markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape showed more improved performance than those of single HTS tape. We explain these results using the change of the spatial distribution and magnitude of self-field on HTS tapes by the neighboring magnetic materials.

DOI： 10.1541/ieejpes.127.327

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冷凍機冷却低温超電導コイルへの有効電力法に基づくクエンチ保護システム適用に関する基礎的検討

竹内和哉, 七戸希, 村瀬暁, 金錫範, 西島元, 渡辺和雄, 竹内孝夫, 伴野信哉, 菊池章弘

低温工学 42 ( 11 ) 382 - 388 2007

A pilot grogram to promote a venture business by undergraduate at Department of Electric and Electronic Engineering in Okayama University

KIM SeokBeom

The Papers of Technical Meeting on Frontiers in Education, IEE Japan 2006 ( 30 ) 13 - 16 2006.12

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