• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.801-803
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• 2000

The large scale magnets like thermalnuclear fusion devices are necessary for superconducting CICC cable, When the Cable In Conduit Conductors(CICC) is occurred by the external turbulence, the CICC occurs to quench, The CICC can be broken because the CICC spends all energy in the quench-happened spot. Therefore, it is necessary to develop measurement systems of the quench detection. The measurement systems of the relative good degree of efficiency are the voltage tap sensors. The weak points of voltage tap sensors are effected by EMF noise and inductance. The thermalnuclear fusion devices easily can't measure inductance value because of plasma current. In the experiment, The value of inductance was estimated by FEM techniques and the decrement of Inductance value measured as long as remaining plasma current.

• 한국초전도ㆍ저온공학회논문지
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• 제13권4호
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• pp.1-4
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• 2011

From the viewpoint of high field application, the mechanical and critical current properties of recently developed $REBa_2Cu_3O_y$ (RE123, RE: rare-earth) coated conductors are summarized. In addition, effective flux pinning mechanisms in RE123 are also introduced. As one of the examples for high field application, the upgrading of the 18 T cryogen-free superconducting magnet is shown. The large anisotropy of $J_c$ is a problem at low temperature and high magnetic field. The nanorod is considered as the useful methods to improve the anisotropy of $J_c$, although its efficiency becomes small at low temperature.

• Structural Engineering and Mechanics
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• 제4권6호
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• pp.613-630
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• 1996

The homogenization method is used to develop a beam element in space for thermo-mechanical analysis of unidirectional composites. Local stress and temperature field in the microscale are described using the function of homogenization. The global (macroscopic) behaviour of the structure is supposed to be that of a beam. Beam-type kinematical hypotheses (including independent shear rotations) are hence applied and superposed on the microdescription. A macroscopic stiffness matrix for such a beam element is then developed which contains the microscale properties of the single cell of periodicity. The presented model enables us to analyse without too much computational effort complicated composite structures such as e.g. toroidal coils of a fusion reactor. We need only a FE mesh sufficiently fine for a correct description of the local geometry of a single cell and a few of the newly developed elements for the description of the global behaviour. An unsmearing procedure gives the stress and temperature field in the different materials of a single cell.

• 한국초전도ㆍ저온공학회논문지
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• 제20권4호
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• pp.31-35
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• 2018

When REBCO coated conductors (CCs) are applied to superconducting devices such as coils and magnets, they are subjected to deformation in various modes such as compression/tension bending, uniaxial/transverse tension and torsion. Despite outstanding performances by REBCO CC tapes, their electromechanical properties have been evaluated primarily under uniaxial tension, therefore data about the critical current ($I_c$) response in the compressive strain region are lacking. In this study, the characteristic responses of $I_c$ in REBCO CC tapes under bending strains in the range from tensile to compressive were evaluated. The springboard bending beam was used, wherein the CC tape sample was soldered onto the surface of the springboard. A Goldacker-type bending test rig, which lacks a support holding the sample during testing, was used as a comparator. Degradation in $I_c$ behaviors, including strain sensitivity, in differently processed REBCO CC tapes were examined based on the test rig used.

• 전력전자학회논문지
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• 제27권5호
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• pp.397-401
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• 2022

The construction of the ITER tokamak machine is ongoing at a 77% process rate to achieve the first plasma in 2025. The 18 sets of power supply systems comprising 400 MVA thyristor AC/DC converters for the superconducting magnets supplied by Korea (KO) are being installed with other systems, such as PF converters (China), DC busbars (Russia), and cooling water systems (India), in two buildings (Europe). The system interfaces have been defined during the design stage, and the systems have been manufactured. However, during the on-site installation work, several installation and integration issues emerged due to the manufacturing tolerance and design mistakes. To continue the installation and testing, the engineers of each system resolved the interface issues, planned the commissioning, and integrated the test plan. This paper describes the on-site installation status and issues and the commissioning plan of KO AC/DC converters.

• 한국초전도ㆍ저온공학회논문지
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• 제12권2호
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• pp.21-24
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• 2010

This paper deals with numerical analysis on a high-$T_c$ superconducting (HTS) electrodynamic suspension (EDS) simulator according to the variation of the ground conductor conditions. Because the levitation force of EDS system is formed by the magnetic reaction between moving magnets and fixed ground conductors, the distribution of the magnetic flux on a ground conductor plays an important role in the determining of the levitation force level. The possible way to analyze HTS EDS system was implemented with 3D finite element method (FEM) tool. A plate type ground conductor generated stronger levitation force than ring type ground conductor. Although the outer diameter of Ring3 (335 mm) was larger than that of Ring2 (235 mm), the levitation force by Ring2 was stronger than that by Ring3. Considering the results of this paper, it is recommended that the magnetic flux distribution according to the levitation height and magnet current should be taken into account in the design of the ground conductors.

• 한국초전도ㆍ저온공학회논문지
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• 제26권1호
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• pp.1-4
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• 2024

This study explores the use of a bulk type high-temperature superconductors (HTS) as trapped field magnets in synchronous motors. A HTS bulk is examined for its ability to generate powerful magnetic fields over a permanent magnet and to eliminate the need for a direct power supply connection compared to a tape form of HTS. A 150 kW interior-mounted bulk-type superconducting synchronous motor is designed and analyzed. The A-H formulation is used to numerical analysis. The results show superior electrical performance and weight reduction when comparing the designed model with the conventional permanent magnet synchronous motor of the same topology. This study presents HTS bulk synchronous motor's overall design process and highlights its potential in achieving relatively high power density than conventional permanent magnet synchronous motor.

• 한국초전도ㆍ저온공학회논문지
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• 제18권1호
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• pp.59-63
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• 2016

The superconducting NMR magnets have used cryogen such as liquid helium for their cooling. The conduction cooling method using cryocoolers, however, makes the cryogenic cooling system for NMR magnets more compact and user-friendly than the cryogen cooling method. This paper describes the thermal and structural analysis of a cryogenic conduction cooling system for a 400 MHz HTS NMR magnet, focusing on the magnet assembly. The highly thermo-conductive cooling plates between HTS double pancake coils are used to transfer the heat generated in coils, namely Joule heating at lap splice joints, to thermal link blocks and finally the cryocooler. The conduction cooling structure of the HTS magnet assembly preliminarily designed is verified by thermal and structural analysis. The orthotropic thermal properties of the HTS coil, thermal contact resistance and radiation heat load are considered in the thermal analysis. The thermal analysis confirms the uniform temperature distribution for the present thermal design of the NMR magnet within 0.2 K. The mechanical stress and the displacement by the electromagnetic force and the thermal contraction are checked to verify structural stability. The structural analysis indicates that the mechanical stress on each component of the magnet is less than its material yield strength and the displacement is acceptable in comparison with the magnet dimension.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권8호
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• pp.404-410
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• 2006

Toward the practical applications, on operation of conduction-cooled HTS SMES at temperatures well below 40[K] should be investigated, in order to take advantage of a greater critical current density of HTS and considerably reduce the size and weight of the system. In order to take advantage of a greater critical current density of high temperature superconducting (HTS) and considerably reduce the size and weight of the system, conduction-cooled HTS superconducting magnetic energy storage (SMES) at temperatures well below 40[K] should be investigated. This work focuses on the breakdown and flashover phenomenology of dielectrics exposed in air and/or vacuum for temperatures ranging from room temperature to cryogenic temperature. Firstly, we summarize the insulation factors of the magnet for the conduction cooled HTS SMES. And Secondly a surface flashover as well as volume breakdown in air and/or vacuum with two kind insulators has been investigated. Finally, we will discuss applications for the HTS SMES including aging studies on model coils exposed in vacuum at cryogenic temperature. The commercial application of many conduction-cooled HTS magnets, however, requires refrigeration at temperatures below 40[K], in order to take advantage of a greater critical current density of HTS and reduce considerably the size and weight of the system. The magnet is driven in vacuum condition. The need to reduce the size and weight of the system has led to the consideration of the vacuum as insulating media. We are studying on the insulation factors of the magnet for HTS SMES. And we experiment the spacer configure effect in the dielectric flashover characteristics. From the results, we confirm that our research established basic information in the insulation design of the magnet.

• 전력전자학회논문지
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• 제19권5호
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• pp.399-406
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• 2014

This study investigates the structure and operation of the ITER VS converter and proposes a sequence control method for six series-connected VS converters to reduce reactive power. The operation and the proposed sequence control method are verified through RTDS simulation. The ITER VS converter must supply voltage/current to the superconducting magnets for plasma current vertical stabilization, and the four-quadrant operation must proceed without a zero-current discontinuous section. The operation mode of the VS converter is separated into a 12- and 6-pulse circulating current and transition modes according to the size of the load current. The output voltage of the unit VS converter is limited because of the rated voltage; however, the superconducting coil must increase the operating output voltage. Thus, the VS converter must be connected in a 6-series to provide the required operating output voltage. The output voltage of the VS converters is controlled continuously; however, reactive power is limited within a minimized value of the grid. In this study, the unit converter is compared with converters connected in a 6-series to determine a suitable sequence control method. The output voltage is the same in all cases, but the maximum reactive power is reduced from 100% to 73%. This sequence control method is verified through RTDS simulation.