• 전기의세계
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• 제26권2호
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• pp.57-65
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• 1977

In roder to investigate the influence of treeing on electric breakdown of solid organic insulator the initiation and growing mechanism of tree itself, and the correlation between corona discharge and treeing phenomena in solid orgainc insulating materials, several experiments were carried out by means of needle test on polymethyl-methacrylate. The obtained results showed that the existence of voids in specimen had important effects on initiation voltage of trees and, when the direct voltage was applied, the initiation voltage of trees increased by space charge effect. And also the stagnation phenomena due to the transfer of vacancy cluster or polymekr cage in specimen might beconsidered in process of growth of trees, and corona discharge seemed to be the pre-phenomena of treeing because trees were normally initiated by internal discharge in voids.

• 한국결정성장학회지
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• 제14권6호
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• pp.267-271
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• 2004

우레아 가수분해법을 이용하여 리튬이차전지용 $LiCoO_2$ 양극 분말을 합성하였다. Li/Co 몰비가 다르고 가수분해에 의해 얻어진 전구체는 다양한 온도에서 열처리되었다. 저온상 $LiCoO_2(LT-LiCoO_2)$와 고온상 $LiCoO_2(HT-LiCoO_2)$는 $500^{\circ}C$에서 2시간 열처리 후 합성되었고, 저온상에서 고온상으로 상전이는 $700^{\circ}C$ 이상에서 완전히 일어났다. 열처리 온도가 증가함에 따라 $LiCoO_2$의 층상구조가 잘 발달하였다. 충방전 실험결과 Li/Co의 몰비가 1.2이고 $800^{\circ}C$에서 열처리한 $LiCoO_2$의 초기용량이 152 mAh/g으로 높았으며, 40회 충.방전 후에는 9.2%의 용량감소를 나타내는 상대적으로 안정한 충방전 특성을 나타내었다.

• 한국수소및신에너지학회논문집
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• 제13권4호
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• pp.259-269
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• 2002

A battery based on the lithium/elemental sulfur redox couple has the advantage of high theoretical specific capacity of 1,675 mAh/g-sulfur. However, Li/S battery has bad cyclic durability at room temperature due to sulfur active material loss resulting from lithium polysulfide dissolution. To improve the cycle life of Li/S battery, PEGDME (Poly(ethylene glycol) dimethyl ether) 500 containing 1M LiTFSI salt which has high viscosity was used as electrolyte to retard the polysulfide dissolution and nano-sized $Mg_{0.6}Ni_{0.4}O$ was added to sulfur cathode as additive to adsorb soluble polysulfide within sulfur cathode. From experimental results, the improvement of the capacity and cycle life of Li/S battery was observed( maximum discharge capacity : 1,185 mAh/g-sulfur, C50/C1 = 85 % ). Through the charge-discharge test, we knew that PEGDME 500 played a role of preventing incomplete charge-discharge $behavior^{1,2)$. And then, in sulfur dissolution analysis and rate capability test, we first confirmed that nano-sized $Mg_{0.6}Ni_{0.4}O$ had polysulfide adsorbing effect and catalytic effect of promoting the Li/S redox reaction. In addition, from BET surface area analysis, we also verified that it played the part of increasing the porosity of sulfur cathode.

• Advances in Energy Research
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• 제8권1호
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• pp.41-57
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• 2022

Electrochemical double-layer capacitors (EDLCs) based on solid polymer electrolytes (SPEs) have gained an immense recognition in the present world due to their unique properties. This study is about preparing and characterizing EDLCs using a natural rubber (NR) based SPE with natural graphite (NG) electrodes. NR electrolyte was consisted with 49% methyl grafted natural rubber (MG49) and zinc trifluoromethanesulfonate ((Zn(CF₃SO₃)₂-ZnTF). It was characterized using electrochemical impedance spectroscopy (EIS) test, dc polarization test and linear sweep voltammetry (LSV) test. NG electrodes were made using a slurry of NG and acetone. EIS test, cyclic voltammetry (CV) test and galvanostatic charge discharge (GCD) test have been done to characterize the EDLC. Optimized electrolyte composition with NR: 0.6 ZnTF (weight basis) exhibited a conductivity of 0.6 x 10^-4 Scm^-1 at room temperature. Conductivity was predominantly due to ions. The electrochemical stability window was found to be from 0.25 V to 2.500 V. Electrolyte was sandwiched between two identical NG electrodes to fabricate an EDLC. Single electrode specific capacitance was about 2.26 Fg^-1 whereas the single electrode discharge capacitance was about 1.17 Fg^-1. The EDLC with this novel NR-ZnTF based SPE evidences its suitability to be used for different applications with further improvement.

• Advances in Energy Research
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• 제7권1호
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• pp.21-34
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• 2020

Energy storage devices have received a keen interest throughout the world due to high power consumption. A large number of research activities are being conducted on electrochemical double layer capacitors (EDLCs) because of their high power density and higher energy density. In the present study, an EDLC was fabricated using natural graphite based electrodes and ionic liquid (IL) based gel polymer electrolyte (GPE). The IL based GPE was prepared using the IL, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (1E3MITF) with the polymer poly(vinyl chloride) (PVC) and the salt magnesium trifluoromethanesulfonate (Mg(CF₃SO₃)₂ - MgTF). GPE was characterized by electrochemical impedance spectroscopy (EIS), DC polarization test, linear sweep voltammetry (LSV) test and cyclic voltammetry (CV) test. The maximum room temperature conductivity of the sample was 1.64 × 10^-4 Scm^-1. The electrolyte was purely an ionic conductor and the anionic contribution was prominent. Fabricated EDLC was characterized by EIS, CV and galvanostatic charge discharge (GCD) tests. CV test of the EDLC exhibits a single electrode specific capacitance of 1.44 Fg^-1 initially and GCD test gives 0.83 Fg^-1 as initial single electrode specific discharge capacitance. Moreover, a good stability was observed for prolonged cycling and the device can be used for applications with further modifications.

• 한국컴퓨터산업학회논문지
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• 제3권12호
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• pp.1651-1658
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• 2002

최근 들어 우리나라에서는 설치의 간편성과 높은 신뢰도를 가진 전력케이블의 사용이 증가하고 있다. 전력케이블은 출고 전에 IEEE std. 404-1993 시험을 거쳐 안정성을 확인하고 있지만 포설시 발생하는 접속부 내부의 결함으로 인하여 많은 문제가 발생하고 있다. 특히 불순물 혼입 또는 공극 발생시 고장율은 증가하게 된다. 부분방전 검출은 포설 후 전력케이블의 상태를 관측할 수 있는 유용한 방법이다. 본 연구에서는 부분방전 특성을 평가하고자 케이블 접속재인 EPR과 케이블 절연체인 XPLE 사이에 인공 결함을 발생시킨 후 데이터 취득 시스템을 이용하여 ${\varphi}$-q-n 특성을 검출하였으며, 부분방전의 정량적 해석을 위해 필요한 통계량인 최대방전전하량($q_{max}$), 평균방전 발생 펄스 수(${\={n}$), 평균 방전전하량(${\={q}$), ${\={n}$의 언밸런스 비와${\={q}$의 언밸런스 비를 계산하였다.

• Korean Chemical Engineering Research
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• 제50권6호
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• pp.1043-1048
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• 2012

본 논문에서는 전기이중층 커패시터(EDLC, Electrical Double Layer Capacitor)의 전극소재로 쓰이는 활성탄소의 안정화를 위해 산소함유관능기를 최소화하고 질소함유관능기의 도입을 통해 유기용액계의 전해질을 가지는 EDLC의 축전용량을 개선하는 연구를 하였다. 주사전자현미경(SEM, Scanning Electron Microscopy), 후리에 변환 적외선분광기(FTIR, Fourier Transform Infrared), 자동원소분석기(EA, Elemental Analysis), 보엠(Boehm) 적정법, 충 방전 테스트 등의 분석법을 이용하여 그 결과를 확인하였다. 산 처리를 통하여 산소함유관능기가 도입되고 요소처리를 통하여 질소함유관능기가 도입되었음을 확인하였다. 질소함유관능기 도입을 통하여 EDLC의 g 당 방전용량을 2 mA 상승시켰으며 빠른 속도로 최대 충 방전 성능을 달성하였다. 반면 산소함유관능기는 전해질 속의 전하가 탄소표면에 흡 탈착되는 것을 방해하기 때문에 낮은 방전용량을 보였고, 충 방전 횟수가 늘어남에 따라 방전용량의 큰 감소를 보여주었다.

• 설비공학논문집
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• 제27권6호
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• pp.321-327
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• 2015

This study presents an HFC152a refrigerant air conditioner as an alternative to HFC134a, which is currently used in mobile air conditioning systems. Cool-down performance tests of an HFC152a air conditioning system were conducted and compared to a baseline HFC134a air conditioner. The experimental set-up consisted of a belt-driven compressor, a sub-cooled type condenser, an evaporator, and a block-type thermal expansion valve (TXV). A drop-in test was carried out on the mobile air conditioning system under various vehicle running speeds in a climate-controlled wind tunnel (CWT). Additionally, to optimize the HFC152a air conditioning system, the effects of the TXVs on the performance were studied. The results show that compared to the HFC134a air conditioning system, the refrigerant charge quantity was reduced by approximately 20%, the discharge pressure was reduced by about 350~430 kPa, and the air discharge temperature at vehicle running conditions was $0.5{\sim}1.5^{\circ}C$ lower. In addition, good compressor durability was expected due to the lower compression ratio.

• 한국초전도ㆍ저온공학회논문지
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• 제14권4호
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• pp.41-45
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• 2012

An HTS (high temperature superconducting) coil without insulation has been investigated since a metallic insulation was suggested in the mid-1980s. The advantage of an insulationless HTS pancake coil is that it is more stable than an insulated HTS pancake coil. This paper focuses on the various characteristics of the insulationless HTS pancake coil related with stability, especially under the external magnetic field. Because HTS pancake coil may be influenced by the external magnetic field in a real operational environment of electrical devices. First, charge-discharge test was performed for the characteristics evaluation of the insulationless HTS pancake coil as compared with insulated HTS pancake coil in liquid nitrogen at 77 K. Based on the experiment results, characteristics evaluation of the insulationless HTS pancake coil was implemented under the external magnetic field. In order to carry out the experiment, we have fabricated a cylindrical solenoid coil to apply the magnetic field. The various characteristics of the insulationless HTS pancake coil were evaluated for charge-discharge and over-current conditions. This paper proves that the insulationless HTS pancake coil is more stable than the insulated HTS pancake under the external magnetic field.

• 전기학회논문지
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• 제64권12호
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• pp.1776-1781
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• 2015

Electric power trains receive electric power from overhead cables via a pantograph system. Power collector system in trains increase the cross section of tunnel and require a massive coreless filter reactor in propulsion inverter because of the power disturbance by contact loss phenomenon of a train. In this paper we proposed a wireless train which can run to next station with charging energy of ultra-capacitor module block. We designed DC-DC converter to charge and discharge ultra-capacitor modules by using Next Train running test results and confirm the feasibility of the proposed system through simulation.