• 한국전기전자재료학회논문지
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• 제18권8호
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• pp.753-758
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• 2005

A flux-lock type superconducting fault current limiter(SFCL) consists of two coils, which are wound in parallel each other through an iron core, and a high-$T_c$ Superconducting(HTSC) thin film connected in series with coil 2. If the current of the HTSC thin film exceeds its critical current by the fault accident, the resistance of the HTSC thin film generated, and thereby the fault current can be limited by the impedance of the fluk-lock type SFCL. In this paper, we investigated the dependence of both the fault current limiting characteristics and the current distribution between two coils on the operational current of the flux-lock type SFCL through the equivalent circuit analyses and short circuit tests. From the comparison of both the results, the experimental results well agreed with the analyses for equivalent circuit.

• 한국초전도ㆍ저온공학회논문지
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• 제13권1호
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• pp.12-16
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• 2011

In this paper, the prototype of the HTS motor with an on-board cryocooler, is fabricated and tested. The overall system is composed of the stator with conventional copper winding, the rotor with superconductor, and the rotating cryocooler designed from the on-board concept. The rotor is fabricated as the race-track coil with 2G, YBCO tape and contacts with the on-board cryocooler while being rotated together. An inline-type pulse tube refrigerator is used as the on-board cryocooler. The cryocooler is fabricated from optimal process to satisfy the structure and thermal stability of the on-board system. Each component is integrated according to carefully defined sequence. Specially, a combining method of torque tubes is an important part for sustaining stability of the rotor and the cryocooler. In the rotating test, the HTS motor is successfully operated with 240 rpm of rotating speed when 75 A current is supplied to the superconducting rotor. In this paper, potential problems of the HTS motor system using the on-board cryocooler are proposed and solved, and realistic possibility of this concept is also confirmed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.766-767
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• 2008

임계온도가 높아 시스템응용에서 매우 안정한 장점을 지닌 고온초전도(HTS)도체를 이용한 HTS-SMES(Superconducting Magnetic Energy Storage)장치에 대하여 많은 연구가 진행되고 있다[1]-[2]. 이런 HTS-SMES 장치의 고가성, 복잡성 등 원인에 기인하여 운전에 앞서 장치의 임계전류, 자속유동손실 및 충.방전시 불가피하게 발생되는 교류손실 등과 같은 기본적인 특성들이 선행하여 연구되어야 한다. 따라서 본 연구에서는 600 kJ급 HTS-SMES코일에 대한 자장분석을 기반으로 코일의 임계전류밀도 분포를 계산하였고 최소 임계전류밀도에 근거하여 코일의 임계전류를 결정하였다. 그 주요 결과를 요약하면 코일에서 자장과 임계전류밀도 분포는 코일의 형상에 무관하게 같은 분포 경향을 보여주며 최소 임계전류밀도는 코일의 top과 bottom의 중심에 위치하며, model코일에서 임계전류의 계산값과 측정값이 비교적 잘 일치하였기 때문에 600 kJ급 HTS-SMES코일도 잘 일치할 것으로 사료된다. 또한 SMES코일을 20 K에서 운전한다고 가정하면 코일 임계전류의 ${\sim}60%$, 4.2 K에서는 ${\sim}40%$에서 각각 운전하게 될 것으로 예측된다.

• 한국초전도ㆍ저온공학회논문지
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• 제4권2호
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• pp.31-37
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• 2002

A 100 〔HP〕 rated synchronous motor with superconducting rotating field winding has been designed based on the formulated equations established from 2 dimensional magnetic field distributions in a cylindrical coordinate The cross-section was drawn based on calculated design results via Fortran program and then modeled with FEM (Finite Element Method) to investigate the machine performances. First of all, the magnetic field distributions are analysed in many ways according to the field directions and the armature currents. Especially after the rotating Held winding is arranged with BSCCO-2223 high-temperature superconducting(HTS) pancake coils, the exerted magnetic field normally on the HTS tape is calculated through FEM. And the machine output power is calculated according to the torque ang1es which lie between the field and the armature main flux lines. Moreover, this Paper includes the eddy-current loss variations of a copper damper located between the field and the armature coils and design considerations of the 100 HP HTS motor utilizing ferro-magnetic material.

• 대한의용생체공학회:의공학회지
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• 제18권4호
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• pp.421-428
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• 1997

초전도양자간섭소자(SQUID)를 이용한 자장센서는 현재 개발된 자장센서중에서 감도가 가장 우수한 소자로서 인체의 두뇌에서 발생하는 매우 미약한 자장에 측정이 가능하다. 뇌자도측정은 현재 많이 사용되고 있는 전기적인 측정(뇌파, 뇌유발전위) 에 비해 공간분해능이 우수하고, fMRI나 PET에 비해서는 시간분해능이 우수하므로 뇌기능연구에 유용하게 사용될 수 있다. 본 연구에서는 뇌자도 측정을 위하여 4-채널 SQUID시스템을 개발하였다. 개발된 시스템의 주요 특징은 새로운 방식의 SQUID센서를 채택함으로서 간단한 회로로써 SQUID구동이 가능하도록 하였으며, 검출코일의 신뢰성을 향상시키기 위하여 집적화된 평면형 코일을 사용하였다. 외부 환경잡음을 소거하기 위하여 자기차폐실을 설치하였고, 개발된 SQUID 시스템을 이용하여 뇌의 청각령으로부터 발생하는 자기신호를 측정하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제14권1호
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• pp.30-33
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• 2012

A double pancake winding method is widely used to make the superconducting magnet, using high temperature superconductor (HTS) tape. In the double pancake winding method, the joints with contact resistances between double pancake coils are inevitably needed. The electrical joule heating on the contacts causes refrigerant loss during operation. And a space outside the winding, for splices and mechanical support, is more than that for its layer-wound equivalent. In this paper, a double pancake winding method in order to reduce the number of the joints was proposed. Both of the double pancake coils using the conventional winding method and the proposed winding method have been fabricated and tested to make the solution technically feasible in the double pancake winding method. Especially, critical-current tests of the fabricated double pancake coils were conducted in order to show the same performance and confirm contact resistances between double pancake coils.

• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.48-52
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• 2019

Recently, many studies have been reported on the magnetoresistance and Hall effect of REBCO thin films and bulk. The voltage interferes quench detection of high-temperature superconducting magnet and generates leakage current in no insulation high-temperature superconducting coil. Therefore, in this paper, experiments on magnetoresistance and Hall effect of commercial YBCO and GdBCO tapes have been carried out. As a result, anomalous voltages expected for the magnetoresistance and Hall effect of REBCO tapes were observed and analyzed. In addition, the voltage characteristics of REBCO have been identified, and the Hall coefficient are calculated for use in high magnetic field magnet applications.

• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.62-66
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• 2020

We fabricated superconducting quantum interference devices (SQUIDs) based on Nb Josephson junctions, and characterized the key parameters of the SQUIDs. The SQUIDs are double relaxation oscillation SQUIDs (DROSs) having larger flux-to-voltage transfer coefficient than the standard DC-SQUIDs. SQUID sensors were fabricated by using Nb junction technology consisted of a DC magnetron sputtering and a conventional photolithography process. In multichannel SQUID systems for whole-head magnetoencephalography measurement with a helmet-type SQUID array, we need about 336 SQUID sensors for each system. In this paper, we fabricated a few hundred SQUID sensors, measured the critical current, flux modulation voltage and decided if each tested SQUID can be used for the multichannel systems. As the criterion for the acceptance of the sensors, we chose the critical current and amplitude of the modulation voltage to be 8 ㎂ and 80 ㎶, respectively. The average critical current of the SQUIDs was 10.58 ㎂. The typical flux noise of the SQUIDs with input coil shorted was 2 μΦ0/√Hz at white region.

• 한국초전도ㆍ저온공학회논문지
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• 제8권2호
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• pp.25-28
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• 2006

The magnet system of KSTAR(korean Superconducting Tokamak Advanced Research) is consisted of 16 TF (Toroidal Field) coils and 14 PF (Poroidal Field) coils. Internal cooling CICC(Cable in Conduit Conductor) type conductor is used for both of TF and PF coil systems. The conduit material for $Nb_3Sn$ cable is Incoloy 908 and 316LN stainless-steel was used as conduit material for NbTi cable. $Nb_3Sn$ CICC is used for all TF coils and PF1-5 coils while NbTi CICC is used for PF6 and 7 coils. $Nb_3Sn$ and NbTi strands were made for KSTAR superconducting strand. They are satisfied with KSTAR superconducotr requirements. The $Nb_3Sn$ strands supplied from three companies; MELCO (Mitsubishi Electric Co.), OAS (Outokumpu Advanced Superconductor) and KAT (Kiswire Advanced Technology) were used. A special CICC jacketing system is developed for the KSTAR CICC fabrication which uses the tube-mill process consisted of forming, welding, sizing and squaring procedures. The. procedures for cabling and jacketing of CICC for TF and PF coils and their results including the geometrical specification and characteristics of strands are described.

• 한국초전도ㆍ저온공학회논문지
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• 제10권3호
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• pp.27-31
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• 2008

In order to cool the SMES coil to the operating temperature, conduction cooling is generally used. However, it often consumes a large amount of electric power because of it's continuous cryocooler operation. This can also lead to poor thermal stability and serious protection problems of the system. Solid nitrogen (SN2) can counter those disadvantages in the conduction cooling system because it has a large heat capacity. Particularly, a large amount of enthalpy with a minimal weight to the cold body of SN2 makes a compact and portable system by increase a recooling to recooling time period (RRTP) value. A conceptual design of the proto-type SN2 cooling system for a portable HTS superconducting magnetic energy storage (SMES) system will be introduced in this paper.