Faculty Profiles - KIM Seokbeom

MISC - KIM Seokbeom

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The levitation characteristics of ferromagnetic materials by ring-shaped HTS bulks with two trapped field distributions

S. B. Kim, J. Matsunaga, Y. Fujii, H. Onodera

IEEE Transactions on Applied Superconductivity 23 ( 3 ) 4603204 2013

Language：English

Stable levitation of cylindrical iron and permanent magnet (PM) samples of various sizes has been achieved by using high temperature superconducting (HTS) bulk annuli which were magnetized by field cooling (FC) method. In this paper, we examined the forces acting on iron and PM samples levitating in the inner space of HTS bulk annuli. The levitation forces of the 3 stacked HTS bulk system (3 bulks system) have been compared withthe 2 stacked HTS bulk system (2 bulks system) having a gap between the bulks. In our experiments, the levitation force increases with increasing the magnetization field strength, the strength of magnetic flux density of PM, and the sample size. The levitation force of the 2 bulks system was better than the 3 bulks system, and we found that the levitation force using the field in magnetized HTS bulk systems strongly depends on the strength of the magnetic flux density of the sample and the magnetic field gradient in the levitating space. © 2002-2011 IEEE.

DOI： 10.1109/TASC.2013.2242513

The improved transient stabilities of HTS coils by removing the insulation and inserting the metal tapes

S. B. Kim, H. Kajikawa, H. Ikoma, J. H. Joo, J. M. Jo, Y. J. Han, H. S. Jeong

PROCEEDINGS OF THE 25TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS2012) 45 249 - 252 2013

Language：English Publisher：ELSEVIER SCIENCE BV

NMR/MRI magnets have a protection device to prevent the damages due to a quench. On the other hand, the protection device design of HTS coils or magnets are very difficult because it has a very low normal zone propagation velocity (NZPV) and complicate behaviors of quench. We have studied the methods to improve the self-protection ability of HTS coils by removing the turn-to-turn insulation and inserting the metal tape instead of insulation. In this paper, the improved transient stabilities and self-protection abilities of HTS coils by removing the insulation and inserting metal tapes will be presented by minimum quench energy (MQE). (C) 2013 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2013.05.014

Numerical and Experimental Study to Fabricate the New Type Compact NMR Device Using Stacked HTS Bulks

S. B. Kim, T. Kimoto, Y. Yano, S. Hahn, Y. Iwasa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22 ( 3 ) 4302004 - 4302004 2012.6

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

In fabrication of a compact NMR (Nuclear Magnetic Resonance) magnet which consists of a stacked HTS (High Temperature Superconducting) bulk annuli, generally there are three key issues: spatial homogeneity, temporal stability, strength of trapped magnetic fields. This paper presents a study on the effects of axial gap length between stacked HTS bulks on the three key issues of a bulk HTS magnet for compact HTS NMR applications. The HTS bulk magnet of which the ID and OD are 20 and 60 mm respectively has a 50 and 80 mm heights depending on the axial gap lengths between HTS bulks. The gap length between each HTS bulk varied from 0 mm to 10 mm and were used as parameters to optimize, analytically as well as experimentally, the overall field homogeneity of the HTS bulk magnet. The optimized axial gap length was obtained by analytical results, and the better magnetic field homogeneity and temporal stability of trapped magnetic field were achieved by lower magnetization field. The improved spatial homogeneity and strength of generated magnetic field by a new compact NMR magnet will be presented.

DOI： 10.1109/TASC.2011.2182170

The Characteristics of the Normal-Zone Propagation of the HTS Coils With Inserted Cu Tape Instead of Electrical Insulation

S. B. Kim, A. Saito, T. Kaneko, J. H. Joo, J. M. Jo, Y. J. Han, H. S. Jeong

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22 ( 3 ) 4701504 - 4701504 2012.6

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

In the case of motors and generators, the benefits of using superconductors could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. The high temperature superconducting (HTS) coils wound with HTS conductors have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the conductors have a low thermal conductivity and large specific heat. According to these reasons, in case of HTS coils and magnets, it is difficult to expect the self-protection like as low temperature superconducting (LTS) coils. In this paper, we suggest a method which inserts the Cu tape between turn-turn winding in the HTS coil instead of electrical insulation to improve the self-protection ability of HTS coils. Because the thermal and electrical contacts along the transverse direction are enhanced by inserted Cu tape instead of insulator and the whole thermal stability of HTS coils would be increased. To clarify the quench behavior of this suggested coil, we investigate the normal-zone propagation properties of the fabricated HTS pancake coils wound with 2G conductor and Cu tape under the cryocooled operation using GM cryocooler. The effects of inserted Cu tape and the improved the self-protection ability for the suggested HTS coil will be discussed.

DOI： 10.1109/TASC.2011.2174559

A Study on Characteristics of the Trapped Magnetic Field for HTS Bulk Superconducting Actuator Operated in AC

S. B. Kim, Y. Uwani, J. H. Joo, R. Kawamoto

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 22 ( 3 ) 4700304 - 4700304 2012.6

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

The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contact transportation device which moves freely in space. In our previous work, the unstable movement characteristics of HTS bulk were observed under DC operation, and the AC control system was proposed in order to solve these problems. In this paper, the horizontal movement and the field decay characteristics as a function of the gap length between electromagnet and HTS bulk and the frequency of driving current were investigated experimentally.

DOI： 10.1109/TASC.2011.2181472

The normal-zone propagation properties of the non-insulated HTS coil in cryocooled operation

S. B. Kim, A. Saitou, J. H. Joo, T. Kadota

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 ( 21-22 ) 1428 - 1431 2011.11

Language：English Publisher：ELSEVIER SCIENCE BV

High temperature superconducting (HTS) coils wound with HTS wires have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the wires have a high thermal stability and large specific heat. According to these reasons, in case of FITS coils and magnets, it is difficult to expect the self-protection like low temperature superconducting (LTS) coils.
In this paper, we suggest a method which can remove the insulation among turn-to-turn in the coil to improve the self-protection property of HTS coils. Because the thermal and electrical contacts along transverse direction are enhanced by no turn-to-turn insulation, the whole thermal stability of HTS coils begins to increase. Furthermore, although a quench occurs in the coil, it is possible to realize a self-protection of HTS coil because the current path of the coil is modified in order to avoid quenching. To confirm a quantitative evaluation for quench behavior of the suggested coil, we carried out the measurements with the coils having variety types of turn-to-turn insulation. The experimental results and the self-protection ability about the tested coils will be presented. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2011.05.209

The characteristics of spatial homogeneity and strength of magnetic field for compact NMR magnets using stacked HTS bulks with various gap lengths

S. B. Kim, T. Kimoto, M. Imai, Y. Yano, J. H. Joo, S. Hahn, Y. Iwasa, M. Tomita

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 ( 21-22 ) 1454 - 1458 2011.11

Language：English Publisher：ELSEVIER SCIENCE BV

A compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of an high temperature superconducting (HTS) bulk. In design of a compact NMR magnet which consists of the stacked HTS bulk annuli, the issues of strength, spatial homogeneity and temporal stability by trapped magnetic fields are very important. This paper presents a study on the effects of magnetization field strength and gap length between stacked bulks for the compact HTS bulk NMR applications. Four-stacked HTS bulk magnet with ID 20 mm and OD 60 mm was prepared to investigate the optimized configuration. The thickness of each HTS bulk is 5 mm, and the gap lengths from 0 mm to 10 mm were used as parameters in analysis and experiment, respectively. Four-stacked HTS bulk magnets with various gap lengths were tested at two different background magnetic fields of 0.5 T and 2 T at 77 K. The optimized axial gap length was found out by analytical results, and the better magnetic field homogeneity and temporal decay property of trapped magnetic field were obtained by lower magnetization field in this experiments. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2011.05.215

The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

S. B. Kim, Y. Uwani, J. H. Joo, R. Kawamoto, Y. S. Jo

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 471 ( 21-22 ) 1479 - 1482 2011.11

Language：English Publisher：ELSEVIER SCIENCE BV

The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HIS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HIS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2011.05.220

Simulation of Magnetic Fluid to Develop the Magnetic Chromatography for Magnetic Particle Separation

So Noguchi, SeokBeom Kim

IEEE TRANSACTIONS ON MAGNETICS 47 ( 10 ) 3947 - 3950 2011.10

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

A magnetic chromatography is a very useful system for an ion and/or fine magnetic particle separation. Recently, its performance has been enhanced using a superconducting magnet. The superconducting magnet can generate a high magnetic field and its strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the fine particles. However, its numerical simulation is difficult, since the scale of the fine magnetic particles in fluid is much different from the scale of the superconducting magnet generating the strong magnetic field. In order to accurately simulate the magnetic separation, it is necessary to develop the simulation code dealing with the multiscale. The performance of the developed magnetic chromatography is evaluated by the developed simulation tool, and it is clarified that it is unsuitable for magnetic particle separation. Therefore, a magnetic chromatography is newly designed and its performance is evaluated by the developed simulation tool.

DOI： 10.1109/TMAG.2011.2158989

Study on Optimized Configuration of Stacked HTS Bulk Annuli for Compact NMR Application

S. B. Kim, M. Imai, R. Takano, J. H. Joo, S. Hahn

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 2080 - 2083 2011.6

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

In design and manufacture of a compact NMR (nuclear magnetic resonance) magnet which consists of a stack of high temperature superconducting (HTS) bulk annuli, spatial homogeneity and temporal stability of trapped magnetic fields are key issues. This paper presents a study on optimized configuration of stacked HTS bulk annuli for the compact NMR application. A three-stack bulk magnet was designed and tested at two different temperatures of 20 and 77 K, and two different background fields of 3 and 5 T. The test results were compared with analytic results to verify the validity of the calculation. Then, various optimized patterns were investigated numerically to find out an optimized stack pattern of HTS bulk annuli in a given condition. The results prove that with the proposed optimized method trapped field strength as well as its homogeneity of a bulk-annulus stack can be improved.

DOI： 10.1109/TASC.2010.2089590

Investigation on Novel Magnetic Chromatography With Ferromagnetic Nano-Wires for Ion Separation

So Noguchi, SeokBeom Kim

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 2068 - 2071 2011.6

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

Magnetic chromatography is a very useful system for ion and/or fine magnetic particle separation due to strong magnetic field gradients in a very small flow channel. We have developed the magnetic chromatography system to separate the ions and fine particles. It is, however, difficult to separate the ions or the magnetic particles using the developed magnetic chromatography. It makes the strong magnetic field gradients in the flow channel, but the alternate direction of the gradient is not suitable for magnetic separation. Therefore, we have newly designed a novel magnetic column with ferromagnetic nano-wires. In this paper, the new magnetic column is presented, and the magnetic field and its gradients in the flow channel are investigated.

DOI： 10.1109/TASC.2010.2090857

Field Performance of an Optimized Stack of YBCO Square "Annuli" for a Compact NMR Magnet

Seungyong Hahn, John Voccio, Stephane Bermond, Dong-Keun Park, Juan Bascunan, Seok-Beom Kim, Tomita Masaru, Yukikazu Iwasa

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 1632 - 1635 2011.6

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

The spatial field homogeneity and time stability of a trapped field generated by a stack of YBCO square plates with a center hole (square "annuli") was investigated. By optimizing stacking of magnetized square annuli, we aim to construct a compact NMR magnet. The stacked magnet consists of 750 thin YBCO plates, each 40-mm square and 80-mu m thick with a 25-mm bore, and has a empty set10 mm room-temperature access for NMR measurement. To improve spatial field homogeneity of the 750-plate stack (YP750) a three-step optimization was performed: 1) statistical selection of best plates from supply plates; 2) field homogeneity measurement of multi-plate modules; and 3) optimal assembly of the modules to maximize field homogeneity. In this paper, we present analytical and experimental results of field homogeneity and temporal stability at 77 K, performed on YP750 and those of a hybrid stack, YPB750, in which two YBCO bulk annuli, each empty set46 mm and 16-mm thick with a 25-mm bore, are added to YP750, one at the top and the other at the bottom.

DOI： 10.1109/TASC.2010.2103920

The Dynamic Characteristics of the HTS Bulk Superconducting Actuator Driven With AC Electromagnets

S. B. Kim, D. Inoue, J. H. Joo, Y. Uwani

IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY 21 ( 3 ) 1519 - 1522 2011.6

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

Electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties due to their strong flux pinning force, has been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device that moves freely in space. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in a clean room where silicon wafers which dislike mechanical contact and dust are manufactured. The proposed actuator consists of an HTS bulk (trapped magnetic field by field cooling method) magnet for the mover and two-dimensional arranged multi-pole electromagnets as the stator. Up to now, the electromagnets consisted with ironed cores and copper coils were used as a stator, and each electromagnet was individually controlled using DC supplies. The movement of HTS bulk (mover) was not smooth because of the DC control. In this paper, the new electromagnets driven with AC control were proposed to improve the moving characteristics of the bulks. The characteristics of horizontal movement by newly proposed system will be presented.

DOI： 10.1109/TASC.2010.2090446

Development of a Numerical Simulation Method for the Magnetic Separation of Magnetic Particles

So Noguchi, SeokBeom Kim

IEEE TRANSACTIONS ON MAGNETICS 47 ( 5 ) 898 - 901 2011.5

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

Magnetic separation is a very useful tool in medicine manufacturing and sludge disposal, and we have developed the magnetic chromatography system, which separates the magnetic particles or the ions from fluid due to its strong magnetic field gradients in the very small flow channel. There are many fine ferromagnetic wires on the wall of the developed magnetic column. A superconducting magnet applies a strong magnetic field to the magnetic column, and fine ferromagnetic wires make strong magnetic field gradients. It was, however, impossible to accurately evaluate the performance of the developed magnetic column due to the absence of a good simulation method. In order to enhance the accuracy of the simulation, it is necessary to couple the fluid dynamics simulation with the magnetic field simulation. Therefore, we have developed a simulation code dealing with the fluid dynamics, solving Navier-Stokes, control volume, and magnetic field equations simultaneously, and compared the simulation result to the experimental one to verify the validity.

DOI： 10.1109/TMAG.2010.2072911

超電導バルク体を用いたアクチュエータの開発

金錫範

超電導Web21 2011

Stability of Toroidal SMES using YBCO Tapes for Simultaneous Quench of a few Coils

So Noguchi, Seok Beom Kim

APPLIED ELECTROMAGNETIC ENGINEERING FOR MAGNETIC, SUPERCONDUCTING AND NANOMATERIALS 670 3 - + 2011

Language：English Publisher：TRANS TECH PUBLICATIONS LTD

We have investigated the stability of 2.0 GJ toroidal HTS-SMES, which consists of 90 element coils wound from YBCO tape. If one or more element coils are quenched, the storage energy reduces due to change of the magnetic field distribution. A series of quench for some element coils may occur, when the energy of the quenched coil cannot be consumed adequately. The simultaneous quench of some element coil may cause the system down. Therefore, it is necessary to investigate the simultaneous quench properties.

DOI： 10.4028/www.scientific.net/MSF.670.3

Numerical Study to Design the New Type Compact NMR Magnet Using HTS Bulk Annuli with High Magnetic Field Performances

S.B. Kim

Proceedings of 18th Conference on the Computation of Electromagnetic Fields 2011

高温超電導バルク体を用いるNMR用マグネットの積層構造最適化に関する研究

金錫範, 今井諒, 木本敬章, 矢野順一, 朱鎮弘

日本ＡＥＭ学会誌 19 ( 2 ) 103 - 108 2011

Characteristics of trapped magnetic fields in HTS bulk annuli with various axial spaces for compact NMR magnets

S. B. Kim, M. Imai, R. Takano, K. Kashima, S. Hahn

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1740 - 1744 2010.11

Language：English Publisher：ELSEVIER SCIENCE BV

Recently, the performance of high-temperature superconducting (HTS) bulks such as a critical current density, size, and mechanical strength has been improved. In consequence, various applications with HIS bulks such as motors, bearings, and flywheels are being investigated by many research groups; Compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of an HIS bulk more than 11.7 T. 500 MHz (1)H NMR frequency, has been developed. This new compact NMR magnet out of FITS bulks is far less expensive than those conventional NMR magnets and expected to be widely used in food and drug industry. In design and manufacture of those compact NMR magnets, the issues of spatial homogeneity and temporal stability of trapped magnetic fields in HTS bulk annuli are very important. In this paper, the characteristics of the trapped magnetic fields in a stack of assembled HIS bulk annuli were investigated with various axial spaces between HTS bulks, experimentally and analytically. (c) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.197

A study on electromagnetic and mechanical characteristics of the field coil in HTS motor

S. B. Kim, T. Kadota, J. H. Joo, H. Sano, S. Murase, S. H. Lee, J. P. Hong, H. M. Kim, Y. K. Kwon, Y. S. Jo

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 ( 20 ) 1756 - 1762 2010.11

Language：English Publisher：ELSEVIER SCIENCE BV

High temperature superconducting (HTS) motors electromagnetically consist of a rotator wound with HTS wires and an armature with conventional copper wires like Litz wire. The HTS rotor windings, as field coils, consist of a straight part and an end-ring part. Because a major rotation torque is induced by an interaction between magnetic fields and current-carrying conductors in the straight part, most of mechanical stresses in the motor occur at the straight part. An end-ring is placed in the edge of the straight part and used to connect to each adjacent straight-part coils. The magnetic fields by coil currents concentrate on the end-ring part, therefore, it is expected that the critical current of the entire coil, straight and end-ring, can be determined by the magnitude of the field in the end-ring. This paper deals with the overall J(c) degradation in the end-ring part by self-field generated from the coil. In addition to electromagnetic analyses, we have performed a numerical analysis in order to evaluate mechanical stresses in the straight part of field coil by armature reaction on steady-state operation. The analytical results will be presented in this paper. (c) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physc.2010.05.201

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