• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.693-694
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• 2006

In order to develop a high temperature superconducting(HTS) coil for the fault current limiter(FCL), the over-current characteristics in YBCO coated conductor(CC) with Ni-W alloy substrate are analyzed. The HTS wire is wound by bifilar winding method for resistive current limitation and it is operated in 65K sub-cooled nitrogen. In order to analyze the resistance and the temperature characteristics of the CC wire, an analysis program is developed considering all the composition materials except the buffer layer. Using this program, the temperature rise, the resistance development and the current limitation of CC are calculated depending on the applied voltage and the stabilizer materials. According to the analysis results, under the temperature restriction of 300K, the maximum voltage per meter is determined as 40V/m if the stabilizer is $25{\mu}m$ thick stainless steel at each side. Finally, the wire length needed for the distribution level HTS FCL is estimated.

• 한국초전도ㆍ저온공학회논문지
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• 제25권4호
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• pp.19-23
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• 2023

The Second-generation high-temperature superconducting (HTS) Rare-Earth Barium Copper Oxide (REBCO) wire is a composite laminate having a multi-layer structure (8 or more layers). HTS wires will undergo multiple loads including the bending-tension loads during winding, high current density, and high magnetic fields. In particular, the wires are subjected to bending stress and magnetic field stress because HTS wires are wound around a circular bobbin when making a high-field magnetic. Each of the different laminated wires inevitably exhibits damage and fracture behavior of wire due to stress deformation, mismatches in thermal, physical, electrical, and magnetic properties. Therefore, when manufacturing high-field magnets and other applications, it is necessary to calculate the stress-strain experienced by high-temperature superconducting wire to present stable operating conditions in the product's use environment. In this study, the finite element model (FEM) was used to simulate the strain-stress characteristics of the HTS wire under high current density and magnetic field, and bending loads. In addition, the result of obtaining the neutral axis of the wire and the simulation result was compared with the theoretical calculation value and reviewed. As a result of the simulation using COMSOL Multiphysics, when a current of 100 A was applied to the wire, the current value showed the difference of 10^-9. The stress received by the wire was 501.9 MPa, which showed a theoretically calculated value of 500 MPa and difference of 0.38% between simulation and theoretical method. In addition, the displacement resulted is 30.0012 ㎛, which is very similar to the theoretically calculated value of 30 ㎛. Later, the amount of bending stress by the circular mandrel was received for each layer and the difference with the theoretically obtained the neutral axis result was compared and reviewed. This result will be used as basic data for manufacturing high-field magnets because it can be expanded and analyzed even in the case of wire with magnetic flux pinning.

• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.51-55
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• 2017

To obtain Nuclear Magnetic Resonance (NMR) measurement of membrane protein, an NMR magnet is required to generate high intensity, homogeneity, and stability of field. A High-Temperature Superconducting (HTS) magnet is a promising alternative to a conventional Low-Temperature Superconducting (LTS) NMR magnet for high field, current density, and stability margin. Conventionally, an HTS coil has been wound by several winding techniques such as Single-Pancake (SP), Double-Pancake (DP), and layer-wound. The DP winding technique has been frequently used for a large magnet because long HTS wire is generally difficult to manufacture, and maintenance of magnet is convenient. However, magnetic field generated by the slanted turns and the splice leads to field inhomogeneity in Diameter of Spherical Volume (DSV). The field inhomogeneity degrades performance of NMR spectrometer and thus effect of the slanted turns and the splice should be analyzed. In this paper, field gradient of HTS double-pancake coils considering the slanted turns and the splice was calculated using Biot-Savart law and numerical integration. The calculation results showed that magnetic field produced by the slanted turns and the splice caused significant inhomogeneity of field.

• 한국항공우주학회지
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• 제46권10호
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• pp.867-875
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• 2018

종래의 큐브위성용 나일론선 절단방식 태양전지판 구속분리장치는 단순히 패널 평면상에 나일론선을 체결함에 따른 취약한 구속력으로 인해 태양전지판 면적이 증가함에 따라 발사하중에 대한 구조 건전성 확보에 한계가 존재한다. 본 연구에서는 전술한 종래 분리장치의 한계점 극복을 위해 Ball & Socket 접속부가 반영된 별도의 타원형 브라켓을 적용하여 높은 구속력, 전개 및 평면 방향 동시구속 및 체결작업의 용이성 등의 장점을 갖는 6U 큐브위성용 태양전지판 구속분리장치를 제안하였다. 상기 구속분리장치의 설계 방향성 파악을 위해 큐브위성용 태양전지판 조립체에 대한 발사하중을 고려한 구조해석을 실시하였다. 또한, 상이한 온도조건에서의 나일론선 두께 및 체결횟수에 따른 기능시험을 수행하여 제안된 구속분리장치의 유효성을 검증하였다.

• 대한기계학회논문집A
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• 제34권3호
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• pp.347-352
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• 2010

원격조정이 불가능한 수중운동체를 제어하기 위해서는 선 유도 제어기술이 효과적으로 사용된다. 스풀에 수십 킬로미터의 길이로 감겨있는 광섬유가 풀릴 때, 수중운동체의 거동과 광섬유의 풀림 속도의 차이에 기인한 큰 장력과 장력 변동이 발생할 수 있다. 이로 인해, 광섬유의 복잡한 거동으로 인한 엉킴 또는 절손의 문제가 발생한다. 그러므로 본 논문에서는 빠른 속도로 풀리는 광섬유의 풀림 동역학 해석을 수행하여 광섬유가 풀리는 동안의 비선형 거동 및 장력, 장력변동을 파악함으로써 설계된 스풀의 풀림 성능을 예측하는 방법을 연구하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제7권4호
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• pp.24-27
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• 2005

Development of a 600 kJ class Superconducting Magnetic Energy Storage (SMES) system is being in progress by Korea Electrotechnology Research Institute(KERI). High temperature superconducting (HTS) wires are going to be used for the windings for the SMES system is presented in this paper. We considered BSCCO-2223 wire for the HTS windings and the operating temperature of the winding was decided to be 20 K which will be accomplished by conduction cooling method using cyro-coolers. Auto-Tuning Niching Genetic Algorithm was adopted for an optimization method of the HTS magnets in the SMES system. The objective function of the optimal process was minimizing total amount of the HTS wire. As a result, we obtained output parameters for optimization design of 600 kJ class SMES under several constrained conditions. These HTS windings are going to be applied to the SMES system whose purpose is stabilization of the power grid.

• Transactions on Electrical and Electronic Materials
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• 제16권1호
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• pp.37-41
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• 2015

The most common structure of the current transformer (CT) consists of a length of wire wrapped many times around a silicon steel ring passed over the circuit being measured. Therefore, the primary circuit of CT consists of a single turn of the conductor, with a secondary circuit of many tens or hundreds of turns. The primary winding may be a permanent part of the current transformer, with a heavy copper bar to carry the current through the magnetic core. However, when the large current flows into a wire, it is difficult to measure its magnitude of current because the core is saturated and the core shows magnetic nonlinear characteristics. Therefore, we proposed a newly designed CT which has an air gap in the core to decrease the generated magnetic flux. Adding the air gap in the magnetic path increases the total magnetic reluctance against the same magnetic motive force (MMF). Using a ferrite core instead of steel also causes the generation of low magnetic flux. These features can protect the magnetic saturation of the CT core compared with the steel core. This technique can help the design of the CT to obtain a special shape and size.

• 전기학회논문지
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• 제58권3호
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• pp.502-508
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• 2009

The method to determine the operating current of HTS magnets needs to be different from that of LTS magnets. This paper presented estimation of the critical current of pancake windings. The pancake windings can be excited by a single power source or by multiple power sources. Critical currents were determined by using field dependent E-J relation. For the better estimation of the critical current, a new method to define the magnetic field of the HTS wire has been proposed. Calculated critical currents of pancake windings were compared with measured ones of the HTS BSCCO magnet consisting of 10 pancake windings. According to the test results, the estimated critical currents of pancake windings agreed well with that of measured ones. Effects of the single and multiple power source excitation on the critical currents have been also examined.

• 전기학회논문지
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• 제63권2호
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• pp.272-276
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• 2014

In this paper, cable drive mechanism is proposed to implement high reduction gear ratio. Cable drive mechanism has great advantages such as light weight, high degree of freedom about design aspect and zero backlashes. However, it is restrictively utilized for robotic applications because it is difficult to implement high reduction gear ratio more than 10 to 1. Proposed mechanism enables multi-level reductions by adopting seamless winding method (SWM) which links the previous output axis and the next input axis. Consequently, this reduces the mechanical complexity significantly and enables high reduction with only one single wire cable. 3D CAD design was provided and prototype was manufactured.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.140-142
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• 1998

The major part of SMES (Superconducting Magnetic Energy Storage) system consist of the superconducting coil, cryostat and current lead, power converter. The 0.7MJ SMES coil was a design and manufacture by using SMES device that we developed a design code. A SMES coil was wound with high winding tension in order to prevent wire motion from Lorentz force. This paper described optimum design for the SMES coil.