• 한국초전도ㆍ저온공학회논문지
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• 제23권4호
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• pp.61-69
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• 2021

This paper presents the analysis and experiment results on the electrical and thermal characteristics of metal insulation (MI) REBCO racetrack coil, which was wound with stainless steel (SS) tape between turn-to-turn layers, under rotating magnetic field and conduction cooling system. Although the field windings of superconducting rotating machine are designed to operate on a direct current, they may be subjected to external magnetic field due to the unsynchronized armature windings during electrical or mechanical load fluctuations. The field windings show the voltage and magnetic field fluctuations and the critical current reduction when they are exposed to an external magnetic field. Moreover, the cryogenic cooling conditions are also identified as the factors that affect the electrical and thermal characteristics of the HTS coil because the characteristic resistance changes according to the cryogenic cooling conditions. Therefore, it is necessary to investigate the effect of external magnetic field on the electrical and thermal characteristics of MI-SS racetrack coil for further development reliable HTS field windings of superconducting rotating machine. First, the major components of the experiment test (i.e., HTS racetrack coil construction, armature winding of 75 kW class induction motor, and conduction cooling system) were fabricated and assembled. Then, the MI racetrack coil was performed under liquid nitrogen bath and conduction cooling conditions to estimate the key parameters (i.e., critical current, time constant, and characteristic resistance) for the test coil in the steady state operation. Further, the test coil was charged to the target value under conduction cooling of 35 K then exposed to the rotating magnetic field, which was generated by three phrase armature windings of 75 kW class induction motor, to investigate the electrical and thermal characteristics during the transient state.

• 한국초전도ㆍ저온공학회논문지
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• 제25권1호
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• pp.16-20
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• 2023

The International Electrotechnical Commission (IEC) 61788-26:2020 provides guidelines for measuring the critical current of Rare-earth barium copper oxide (REBCO) tapes using two methods: linear ramp and step-hold methods. The critical current measurement criterion, 1 or 0.1 μV/cm of electric field from IEC 61788-26 has been normally applied to REBCO coils or magnets. No-insulation (NI) winding technique has many advantages in aspects of electrical and thermal stability and mechanical integrity. However, the leak current from the NI REBCO coil can cause distortion in critical current measurement due to the characteristic resistance which causes the radial current flow paths. In this paper, we simulated the NI REBCO coil by applying both linear ramp and step-hold methods based on a simplified equivalent circuit model. Using the circuit analysis, we analyzed and evaluated both methods. By using the equivalent circuit model, we can evaluate the critical current of the NI REBCO coil, resulting in an estimation error within 0.1%. We also evaluate the accuracy of critical current measurement using both the linear ramp and step-hold methods. The accuracy of the linear ramp method is influenced by the inductive voltage, whereas the accuracy of the step-hold method depends on the duration of the hold-time. An adequate hold time, typically 5 to 10 times the time constant (τ), makes the step-hold method more accurate than the linear ramp method.

• 한국자기학회지
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• 제2권2호
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• pp.156-162
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• 1992

저자장방법으로 양성자 자기회전비율을 측정할 때, 지자장을 상쇄시켜 무자장 실험공간을 형성시킬 필요가 있다. 이를 위해 일정한 자장성분은 헬름홀쯔코일에 흐르는 정전류에 의하여 상쇄 되고, 미소변화 자장은 폐회로를 구성하는 궤환장치에 의해 자동적으로 상쇄되는 지자장 상쇄장치 를 설계하였다. 지자장성분을 상쇄하기 위해 코일상수가 같은 대형 및 소형 3축 헬름홀쯔코일과 미 소변화 자장 상쇄용 궤환증폭기를 제작하였다. 제작된 시스템을 사용하여 일반실험실 내에서 예비 실험을 한 결과 수십 ${\mu}T$ 의 일정한 자장성분과 ${\pm}100nT$ 의 미소변화 자장을 상쇄하여 잔류자 장이 ${\pm}10nT$ 이하인 공간을 형성하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제25권3호
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• pp.38-42
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• 2023

The evaluation of no-insulation (NI) high-temperature superconducting (HTS) typically uses the lumped equivalent circuit (LEC) model. Constant parameters in the NI HTS LEC model accurately predict voltage and central magnetic field at currents below the critical current. However, it is difficult to find constant circuit parameters that simultaneously satisfy the measured voltage and magnetic field under overcurrent conditions. Recent research highlights changes in contact resistance during transient conditions, which may impact power loss estimation in NI HTS coils. Therefore, we confirm the influence of contact resistance changes on loss calculation in the transient state for NI HTS coil. To achieve this, we introduce a measurement data analysis method based on the LEC model and compare it with the LEC model using constant circuit parameters.

• 한국자기학회지
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• 제13권6호
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• pp.251-256
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• 2003

컴퓨터, TV, 의료용기기 등의 모니터로 사용되는 브라운관의 자기장 영향에 따른 특성을 분석하기 위한 자기장 발생 및 측정장치를 개발하였다. 한 변의 길이가 2 m인 정육각형 형태의 3-축 자기장 발생장치, 컴퓨터, 전원공급기 및 자기장 측정기 등을 이용하여 전세계 각 나라별 지구자기장(Earth Magnetic Field, EMF)을 발생시킬 수 있는 대형 3-축 코일 시스템을 설계하고 제작하였다. 각 코일의 코일상수는 X축(E-W)는 30.31 $\mu$T/A, Y축(Ver)는 29.73 $\mu$T/A 및 Z축(N-S)는 30.51 $\mu$T/A이고, 자기장 분해능은 0.01 $\mu$T이었다. 자기장 균일도는 사용되는 편향요크(Deflection York, DY)의 크기를 고려하여 중심에서 12 cm 이내의 공간에서 측정하였고, 균일도는 1 % 내외 이었다.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.246-255
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• 2016

When spring of the suspension is exerted by an external load, a car should be designed to prevent predictable damages and designed for a ride comfort. We used experiments design to design VON-MISES STRESS and K, a constant, of spring of suspension which is installed in a car as a goal level. We analyzed the result from Edison's Elastic - Plastic Analysis SW(CSD_EPLAST) by setting D, d, n as external diameter of coil, internal diameter of coil, the number of total coil respectively. The experiment design let the outcome be as Full-second order by using Box-Behnken which is one of response surface methods. Experimented and analyzed results based on the established experiments design, We found out design parameter which has desired VON-MISES STRESS and the constant K. Additionally, we predicted life time of when the external load was exerted by repeated load by using fatigue equation, and verification of plastic deformation has also been made. Additionally we interpreted a model, which is formed by optimized design parameter, with linear analysis and non-linear analysis, at the same time we also analyzed plastic deformation with the values from the both models. Finally, we predicted fatigue life of optimized model by using fatigue estimation theory and also evaluated a ride comfort with oscillation analysis.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.178-183
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• 2012

The design of the integrated quench protection (QP) system for the high current superconducting magnet (SCM) has been fabricated and tested for the toroidal field (TF) coil system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The QP system is capable of protecting the TF SCM, which consists of 16 identical coils serially connected with a stored energy of 495 MJ at the design operation level at 35.2 kA per turn. Given that the power supply for the TF coils can only ramp up and maintain the coil current, the design of the QP system includes two features. The first is a basic fast discharge function to protect the TF SCM by a dump resistor circuit with a 7 s time constant in case of coil quench event. The second is a slow discharge function with a time constant of 360 s for a daily TF discharge or for a stop demand from the tokamak control system. The QP system has been successfully tested up to 40 kA with a short circuit and up to 34 kA with TF SCM in the second campaign of KSTAR. This paper describes the characteristics of the TF QP systems and test results of the plasma experiment of KSTAR in 2009.

• 대한기계학회논문집A
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• 제37권12호
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• pp.1529-1534
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• 2013

전자기력을 이용한 소형 회전 무빙 자석 타입 보이스 코일 구동기를 소형 이동 로봇을 위해 개발하였다. 1개의 자석과 1개의 코일 그리고 1개의 요크로 이루어진 간단한 구조이다. DC 모터와 같이 선형으로 근사화한 이론적인 모델링으로 성능을 예측하였고, 유한 요소 해석 프로그램으로 모터 상수와 복원력 상수를 계산하여 자석과 코일 사이의 공극에 따른 성능을 예측하였다. 시작품을 제작하여 실험을 통하여 60Hz 에서 공진 주파수를 가지고 주파수 대역폭이 80Hz를 가짐을 확인하여 모델링을 검증하였다. 그리고 정적으로 1.5V 입력 전압으로 약 20 deg의 회전을 확인하였다. 제안된 구동기는 개루프 제어가 가능하여 회로 구성을 간단히 할 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1143-1147
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• 2004

A mechanical type pulsation dampener for the diaphragm metering pump has been developed. The pulsation pressure is an inevitable phenomenon for the positive displacement pump such as cam operated or solenoid operated metering pump. The pulsation pressure of the metering pump could be the noise source and would be harmful for the piping system which delivers hydraulic fluid. Developed pulsation dampener consists of three coil springs which have different spring constant and height each other. Depending on pressure magnitude of the piping system, total hydraulic pressure on damping diaphragm which compresses coil springs will be varied. Force equilibrium of the pulsation dampener will be set by manual by adjusting the compressed coil spring height. During the discharge stroke, pulsation dampener stores potential energy that is released as the pumping diaphragm back to an initial position during the suction stroke.

• 설비공학논문집
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• 제23권11호
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• pp.762-768
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• 2011

We use floor radiant heating system in the house of commons in winter Floor radiant heating system, which transfer heat by radiation, is one of the energy efficient and comfortable systems that. Floor radiant heating system is configured to be controlled by the room for energy-saving. Proper flow rate to a comfortable heating in the room is important. However, Using a constant speed circulation pump in separate rooms, heating system may cause an imbalance because of the difference of length of coil when operating in the rooms. In this study, our Research team examined heating imbalance due to the variation length through the coil length changes and flow control of the circulation pump.