• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.5
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• pp.60-67
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• 2005

The superposed discharge type ozonizer of high ozone concentration using vacuum discharge tube has been designed and manufactured. It consists of three electrodes(central electrode, internal electrode, and external electrode) and one discharge gap(discharge gap between internal electrode and external electrode), is a superposed silent discharge type ozonizer for which the AC high voltages applied to the central electrode within discharge tube and the internal electrode has a $180{[^\circ]}$ phase difference and for which the external electrode is a ground. Ozone is generated by overlapping silent discharge between central electrode and external electrode, and silent discharge between internal electrode and external electrode. At the moment, discharge characteristics and ozone generation characteristics were investigated in accordance with vacuum of discharge tube, discharge power of ozonizer, and quantity of supplied oxygen gas. In consequence, high ozone concentration can be obtained 8840[ppm].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.5
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• pp.87-93
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• 2005

In order to develope high concentration$\cdot$yield ozonizer, superposed discharge type ozonizer using overlap of silent discharge and internal electrode of mesh type has been designed and manufactured. It consists of three electrodes(central electrode, internal electrode and external electrode) and double gaps(gap between central electrode and internal electrode, gap between internal electrode and external electrode). Therefore, ozone is generated by overlapping silent discharges generated between the gaps respectively for which the AC high voltages applied to the internal electrode and the external electrode has a $180{[^\circ]}$ phase difference and for which the central electrode is a ground Ozone generation characteristics proportional to mesh of internal electrode by increasing of discharge electrode and controlling of discharge power density. As a result, the in maximum ozone concentration, generation, and yield can be obtained 17,720[ppm], 5.4[g/h], and 205[g/kwh] respectively.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.40-51
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• 2009

To analyze influences under open faults in switching devices of the PWM inverter and under the isolation between the inverter and motor terminal, a faulty model for the inverter-driven permanent magnet synchronous motor is presented. Even though the conventional dq motor model obtained through the transformation of phase voltage model is widely used to analyze and control AC motor, it can not be used under open faults in switching devices since the 3-phase balanced condition is no longer hold under the open fault and it is not easy to obtain motor input voltages in open phase from the pole voltage. To deal with this problem, a faulty model for an inverter-driven permanent magnet synchronous motor is derived by using the line voltage of motor according to switch open, which can be effectively used for performance evaluation of the diagnostic algorithm. The validity of the proposed faulty model is verified through comparative simulations and experiments using DSP TMS320F28335.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.9
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• pp.62-68
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• 2008

This paper describes the electrical characteristics of ZnO surge arresters associated with the variation of surrounding conditions. To investigate the deterioration behaviors of ZnO surge arresters due to lightning surges, 8/20[${\mu}s$], 2.5[kA] impulse currents were injected to the ZnO surge arrester under test. The leakage currents of ZnO surge arrester subject to power frequency AC voltage were measured in different surrounding temperature and wet conditions. As a result, it was found that the leakage current is increased and its asymmetry is pronounced as the number of injection of the impulse current and the ambient temperature increase. Also, in the wet test the outside leakage current flowing through the housing surface of the ZnO surge arrester is much larger than the intrinsic leakage current of ZnO surge arrester element. The results obtained in this work can be a lied as factors of improving the reliability and performance of monitoring system for surge arresters.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.551-554
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• 2004

Bi-2223 HTS tapes are used widely for application of superconducting power systems. However there are need the properties of high strength and low AC loss. Two kinds of Bi-2223 HTS tapes with different Ag sheath were used to know the effect of sheath alloying for the strength and the resistivity. The workability and reaction degree of superconducting phase at Bi-2223 HTS tapes were investigated. We designed conventional type-Ag/alloy and double sheathed mono filament type-Ag/alloy/alloy in order to increase the strength and resistivity of matrix in Bi-2223 HTS tapes. The effect of axial strain and thermal cycling on the critical current was investigated for the Bi-2223 HTS tapes. Because the workability of double sheath Bi-2223 HTS tape was lower than one sheath Bi-2223 HTS tape, it was need additional softening treatment. Bi-2223 formation reaction was decreased by Ag alloy matrix during sintering process. Two kinds of Bi-2223/Ag tapes with different Ag sheath were used to know the effect of sheath alloying for the tensile strain. Critical current is drastically decreased for Ag/alloy and Ag/alloy/alloy sheathed tapes at tensile strain above 0.24 % and 0.34 %, respectively. This result showed that mechanical strength was increased over than 40 % by introduce double sheath at mono filament stage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.639-642
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• 2005

HTS Transformer developing is developing a power distribution and transmission class HTS transformer that is one of the 21st century superconducting frontier projects. Therefore, we prepared the model, that is Z continuous winding from Kapton insulated Cu tape for a small simulated the HTS transformer. For the development of electrical insulation design of a HTS transformer with Z continuous winding, we have been discussed insulation composition and investigated breakdown characteristics such as breakdown of liquid $N_2(LN_2)$, polymer and surface flashover on FRP and breakdown-surface combination in $LN_2$. Also we have been designed and manufactured a bobbin that has spiral slot for the Z continuous winding. The Z continuous winding mini-model from Kapton film insulated Cu tape for simulated 22.9kV class HTS transformer has been constructed using 0.1 % breakdown strength obtained by Weibull distribution. The widing model was measured their insulation characteristics such as ac (50kV, 1min) and impulse (154kV, $1.2\times50{\mu}s$ full wave, 3 times) withstand test and its excellent performance was confirmed.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.447-447
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• 2010

일찍이 $SiO_2$ (Silicon dioxide) 박막은 다양한 분야에서 유전층, 부식 방지층, passivation층 등의 역할을 해왔다. 그리고 이러한 박막 공정은 대부분 진공의 환경에서 그 공정이 이루어지고 있다. 하지만 이러한 진공 system은 chamber, loadlock 그리고 펌프 등의 다양한 진공장비로 인한 생산 비용 증가, 공정의 복잡성뿐만 아니라 공정의 대면적화에 어려움을 지니고 있다. 그리고 최근 flexible display의 제조 공정에서 polymer 혹은 plastic 기판을 제조 공정에 적용시키기 위해 저온 공정이 필수적으로 요구 되고 있다. 이러한 기술적 한계를 뛰어 넘기 위해 최근 많은 연구가들은 atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD)에 대해 지속적으로 다양한 연구를 하고 있다. 본 연구에서는 remote-type의 modified pin-to-plate dielectric barrier discharge (DBD) 시스템을 이용한 $SiO_2$ 무기 박막 증착에 관해 연구하였다. $O_2$/He/Ar의 gas와 5 kV AC power (30 kHz)의 전원장치를 통해 고밀도 대기압 플라즈마를 발생시켰고, silicon precursor로는 hexamethyldisilazane (HMSD)를 사용하였다. 먼저 HMDS와 $O_2$ gas의 flow rate 변화에 따른 증착률을 조사하였고 그 다음으로 박막의 조성 및 표면 특성을 조사하였다. HMDS의 유량이 100 ~ 300 sccm으로 증가함에 따라 증착속도는 증가했다. 하지만 FT-IR을 통해 HMDS의 유량이 증가하면 반응에 참여할 산소 분자의 부족으로 인해 $-(CH_3)_X$의 peak intensity가 증가하고, -OH의 peak intensity가 점차 감소함을 관찰 할 수 있었다. 또한 증착된 박막의 표면에 particle과 불균일한 surface morphology 등을 SEM image를 통해 관찰 하였다. 산소 유량이 탄소와 관련된 많은 불순물들의 제거에 도움이 됨에도 불구하고 14 slm 이상의 산소가 반응기 내로 주입되게 되면 대기압 플라즈마의 discharge가 불안정하게 되어 공정효율을 저하시키는 요소가 되었다. 결과적으로 HMDS (150 sccm)/$O_2$ (14 slm)/He (5 slm)/Ar (3 slm)의 조건에서 약 42.7 nm/min 증착률을 가지며, 불순물이 적고 surface morphology가 깨끗한 $SiO_2$ 박막을 증착할 수 있었다.

• 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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.2
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• pp.152-159
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• 2019

In general, a Doppler radar can measure only the velocity of a moving target. To measure the distance of a moving target, it is necessary to use a frequency-modulated continuous wave or pulse radar. However, the latter are very complex in terms of both hardware as well as signal processing. Moreover, the requirement of wide bandwidth necessitates the use of millimeter-wave frequency bands of 24 GHz and 77 GHz. Recently, a new kind of Doppler radar using multitone frequency has been studied to sense the distance of moving targets in addition to their speed. In this study, we show that distance sensing of moving targets is possible by adjusting only the frequency of a 2.4 GHz Doppler radar with low cost phase lock loop. In particular, we show that distance can be sensed using only alternating current information without direct current offset information. The proposed technology satisfies the Korean local standard for low power radio equipment for moving target identification in the 2.4 GHz frequency band, and enables multiple long-range sensing and radio-frequency identification applications.

• Progress in Superconductivity and Cryogenics
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• v.23 no.3
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• pp.51-54
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• 2021

The DC system has less power loss compared to the AC system because there is no influence of frequency and dielectric loss. However, the zero-crossing point of the current is not detected in the event of a short circuit fault, and it is difficult to interruption due to the large fault current that occurs during the opening, so the reliability of the DC breaker is required. As a solution to this, an LC resonance DC circuit breaker combined a superconducting element has been proposed. This is a method of limiting the fault current, which rises rapidly in case of a short circuit fault, with the quench resistance of the superconducting element, and interruption the fault current passing through the zero-crossing point through LC resonance. The superconducting current limiting element combined to the DC circuit breaker plays an important role in reducing the electrical burden of the circuit breaker. However, at the beginning of a short circuit fault, superconducting devices also have a large electrical burden due to large fault currents, which can destroy the element. In this paper, the reactor is connected to the source side of the circuit using PSCAD/EMTDC. After that, the change of the fault current according to the reactor capacity and the electrical burden of the superconducting element were confirmed through simulation. As a result, it was confirmed that the interruption time was delayed as the capacity of the reactor connected to the source side increased, but peak of the fault current decreased, the zero-crossing point generation time was shortened, and the electrical burden of the superconducting element decreased.