• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.15-18
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• 2003

Fault current limiters (FCL) are extensively needed to suppress fault currents, especially for trunk power systems heavily connected to high voltage/large current transmission lines. Due to its ideal electrical behavior, high-temperature superconductor fault current limiter (HTSFCL) becomes one of the most important developing trends of limiters in power system. This paper describes the result of an investigation of the dielectric characteristics of turn-to-turn insulation for pancake and solenoid type reactor coil in liquid nitrogen. The influence of thickness in a variety length, on AC, DC and impulse surface flashover has been investigated. Also, the relationships between the number of turn and breakdown characteristics were clarified. The information gathered in this test series should be helpful in the design of liquid nitrogen filled DC reactor type HTSFCL.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.226-229
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• 2003

Following the successful development of practical high temperature superconducting (HTS) wires, there has been renewed activity in the development of superconducting power equipments. HTS equipments must be operated in the coolant, such as liquid nitrogen (L$N_2$) or cooled by cooler, such as GM-cryocooler to maintain the temperature below critical temperature. In this paper, dielectric strength of some insulating materials, such as epoxy, teflon, and glass fiber reinforced plastic (GFRP) in L$N_2$was measured. Surface breakdown voltage of GFRP which is basic property in design of HTS solenoid coil was measured. Epoxy is a goof insulating material but it is fragile at cryogenic temperature. The multi-layer insulating method of current lead is suggested to compensate this fragile property. It consists of teflon tape layer and epoxy layer fixed with texture. Based on these measurements, the 6.6㎸ class HTS magnet for DC reactor type high-T$_{c}$ superconducting fault current limiter (SFCL) was successfully fabricated and tested.d.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.227-228
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• 2015

우리나라가 조달하는 ITER(국제핵융합시험로) 초전도자석 전원장치용 변압기는 CCU/L(Correction Coil Upper/Lower) 컨버터 형식용 6대, CCS(Correction Coil Side) 컨버터 형식용 3대, VS1(Vertical Stabilization 1) 컨버터 형식용 2대, CS(Central Solenoid) 컨버터 형식용 6대 그리고 TF(Toroidal Field) 컨버터 형식용 1대로 구성되어 있다. ITER한국사업단은 (주)효성과 컨버터 변압기의 공급계약을 2011년에 체결하고 예비 설계를 시작하여 2014년에 최종설계를 마친 후 동년 후반부터 CCU/L, CCS 및 VS1 컨버터 형식용 각 1대씩의 초도품 변압기 제작에 착수하였다. 각 변압기는 제작이 완료되어 CCU/L 및 CCS 형식은 FAT(Factory Acceptance Test)를 완료하였고 VS1 형식은 공장 자체시험을 완료하고 현재 전기연구원에서 실시할 단락시험을 준비하고 있다. 이어 CS 형식의 초도품과 1대만 조달하는 TF 형식의 제작을 착수할 예정이고, 각 형식별 초도품 1대씩은 단락시험을 포함하는 형식시험(Type Test)을 실시하여 형식별 적합성을 검증하고, 나머지 물량은 정기시험(Routine Test)을 실시한 후 2017년까지 두 번으로 나누어 프랑스 남부에 위치한 ITER 현장에 운송 및 설치할 예정이다. 설치를 마친 변압기들은 각각의 컨버터 짝과 통합시험을 포함하는 SAT(Site Acceptance Teat)를 거친 후 ITER 기구에 인계될 예정이다.

• Journal of Biomedical Engineering Research
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• v.26 no.6
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• pp.393-398
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• 2005

An electromechanical type is the most useful mechanism in the various pumping mechanisms. It, however, requires a movement converting system including a ball screw, a helical cam, or a solenoid-beam spring, which makes the device complex and may lessen reliability. Thus, the authors have hypothesized that an electromagnetic actuator mechanism can eliminate the movement converting system and that thereby enhance the mechanical reliability and operative simplicity of an electro­pneumatic pump. The purpose of this study was to show a novel application of electromagnetic actuator mechanism in pulsatile pump and to provide preliminary data for further evaluations. The electromagnetic actuator consists of stators with a single winding excitation coil and movers with a high energy density neodymium-iron-boron permanent magnet. A 0.5mm diameter wire was used for the excitation coil, and 1000 turns were wound onto the stators core with parallel. A prototype of extracorporeal electro-pneumatic pump was constructed, and the pump performance tests were performed using a mock system to evaluate the efficiency of the electromagnetic actuator mechanism. When forward and backward electric currents were supplied to the excitation coil, the mover effectively moved back and forth. The nominal stroke length of the actuator was 10mm. The actuator dimension was 120mm in diameter and 65mm in height with a mass of 1.4kg. The prototype pump unit was 150mm in diameter, 150mm in thickness and 4.5kg in weight. The maximum force output was 70N at input current of 4.5A and the maximum pump rate was 150 beats per minute. The maximum output was 2.0 L/minute at a rate of 80bpm when the afterload was 100mmHg. The electromagnetic actuator mechanism was successfully applied to construct the prototype of extracorporeal electro­pneumatic pump. The authors provide the above results as a preliminary data for further studies.

• Investigative Magnetic Resonance Imaging
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• v.13 no.2
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• pp.171-176
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• 2009

Purpose : To investigate the effect of coating material in RF coil, which is one of main parts in MRI machine, on the Q-factor and SNR(signal-to-noise ratio) in MR images. Materials and Methods : RF coils with inner diameter of 1.7 mm were made by using copper wires coated with polyester, polyurethane, polyimide, polyamideimide, and polyester-imide, and by using copper wires in which coating materials had been removed. Q-factors of the RF coils were measured by network analyzer, and SNR values in the spin-echo MR images obtained by 600 MHz (14.1 T, Bruker DMX600) micro-imaging system for the coated and uncoated cases. Results : The measured SNRs were almost same for the RF coils with coat-removed copper wires, however SNRs and Q-factors were different for the coated cases depending on the coating material. They were maximized in the polyurethane-coated case in which the SNR was > 30% greater than polyester-coated case. Conclusion : We made solenoid-type RF coils which were easily used for MR micro-imaging in Bruker MRI probe. There was a significant coating-material dependence in the measured Q values and SNRs for the home-made RF coils. The study demonstrated that the choice of coating material of RF coil may be a critical factor in the MRI sensitivity based on SNR value.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.6
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• pp.34-42
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• 2000

Recently, there is a growing need to develope small-size RF chip inductors operating to GHz to realize high-performance, micro-fabricated wireless communication products. For the development of high-performance RF chip inductors, however, the ferrite-based chip inductors can not be used above 300MHz due to the limitation of the permeability of this material. In this work, small-size, high-performance RF chip inductors utilizing amorphous $Al_2O_3$ core material were investigated. Copper (Cu) with 40${\mu}m$ diameter was used as the coils and the chip inductor size fabricated in this work is $2.1mm{\times}1.5mm{\times}1.0mm$. The external current source was applied after bonding Cu coil leads to gold pads electro-plated on the bottom edges of a core material. The composition of core materials was measured using a EDX. High frequency characteristics of the inductance (L), quality factor (Q), and impedance (Z) of developed inductors were measured using an RF Impedance/Material Analyzer (HP4291B with HP16193A test fixture). The developed inductors have the self-resonant frequency (SRF) of 1 to 3.5 GHz and exhibit L of 22 to 150 nH. The L of the inductors decreases with increasing the SRF. The Z of the inductors has the maximum value at the SRF and the inductors have the quality factor of 70 to 97 in the frequency range of 500 MHz to 1.5 GHz.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.324-330
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• 2016

A magnetic contactor is a switching device widely used for electric circuits. For the operation of magnetic contactors, magnetic coils are essential; these coils create and interrupt the electric circuit. In this paper, the finite element analysis model was developed to reflect the experimental data, and was verified through alteration of the applied voltages and the numbers of turns. Effects of electromagnetic force on the geometrical variations of the facing poles for fixed and moving cores of two magnet coils were investigated. In addition, effects of slope and air gap size between two facing poles on the electromagnetic force were explored through the distribution of the magnetic flux density in the magnetic coils of a push-type solenoid. Through this analysis, the characteristics of the electromagnetic force against the facing poles were explored.

• Korean Journal of Food Science and Technology
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• v.25 no.4
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• pp.391-394
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• 1993

For the automation of Tackjoo fermentation, a sensor measurable gas production during brewing and a controller were built. The performance tests were carried out at 10 litter Tackjoo fermentor, The sensor was consisted of a transparent acryl cell for bubble formation and photo-interrupter for the detection of bubbles of 0.018ml size. The fermentation controller was fabricated with a single chip microcomputer (MC68705R3) and provided with both the monitoring module of temperature measurement and the valve controling device for the cooling water circulation in coil type heat exchanger. The operation programs were developed and systemized in ROM. With this computer system, the gas production amount and rate were acquired during the Tackjoo fermentation. The fermentation curve based on the gas production rate showed a good agreement with that of alcohol concentration. The maximum rate of gas production was found after 24 hr at $30^{\circ}C$. The correlation equation between the gas production and alcohol concentration was established and used as the control algorithm of the fermentation.