• 한국자동차공학회논문집
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• 제5권1호
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• pp.27-37
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• 1997

Internal combustion engine is the main source of environmental pollutants and therefore better technology is required to reduce harmful elements from the exhaust gases all over the world. Especially, harmful elements from the exhaust gases are caused by incomplete combustion of mixture inside the engine cylinder and this abnormal combustion like misfire or partial burning is the direct cause of the air pollution and engine performance degradation. the object of this research is to detect abnormal combustion like misfire and to keep the engine performance in the optimal operating state. Development of a new system therefore could be applied to a real car. To realize this, the spark-plug in a conventional ignition system is used as a misfire detection sensor and breakdown voltage is analyzed. In this research, bias voltage(about 3kV) was applied to the electrodes of spark-plug and breakdown voltage signal is obtained. This breakdown voltage signal is analyzed and found that a combustion phenomena in engine cylinder has close relationship with harmonic coefficient K which was introduced in this research. Newly developed combustion diagnostic method( breakdown voltage signal analysis) from this research can be used for the combustion diagnostic and combustion control system in an real car.

• Journal of Electrical Engineering and Technology
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• 제2권2호
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• pp.257-262
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• 2007

In this paper the experiments of breakdown characteristics by temperature change of $SF_6$ gas($GSF_6$), and $SF_6$ liquid ($LSF_6$) in model GIS (Gas Insulated Switchgear) are described. From the experiment's results, the breakdown characteristics classify the vapor stage of $SF_6$ according to Paschen's law, in which the gas & liquid coexisted stage of voltage value increases, resulting in much deviation and the breakdown of voltage ($V_B$) low stage as the interior of the chamber gets filled with a mixture of $SF_6$ that is not liquefacted and remaining air that cannot be ventilated. The ability of $LSF_6$ insulation is higher than the high-pressurized $SF_6$ gas. The breakdown characteristics of $LSF_6$ were produced by bubble formed evaporation of $LSF_6$ and bubbles caused by high electric emission. It is considered in this paper that the results are fundamental data for electric insulation design of superconductor and cryogenic equipments machinery that will be studied and developed in the future.

• 한국진공학회지
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• 제11권1호
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• pp.68-75
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• 2002

본 연구에서는 운전압력을 1 mTorr~760 Torr까지 변화시키며 발생되는 마이크로파 공기 플라즈마의 특성을 관찰하였다. 마이크로파 공기 플라즈마 발생을 위하여 마이크로파의 전송선로인 도파관은 $TE_{01}$ mode로 설계 및 제작하였으며, 가정용 전자렌지에 사용되는 마그네트론을 이용하여 AC-type microwave source를 제작하였다. 입력 전력은 370 W로 일정하게 유지하였으며, 이때 발생하는 플라즈마의 특성 관찰은 고속주사 정전탐침과 OES (Optical Emission Spectroscopy)를 이용하였다. 최소 절연파괴 전기장의 세기(breakdown E-field)를 가지는 압력인 500 mTorr를 기준으로 발생 플라즈마의 특성은 많은 변화를 보였으며 이 압력은 입력주파수($\omega$)와 충돌주파수($V_c$)가 일치하는 조건이었다. 이때 공기의 유효충돌 단면적은 $9.23\times10^{-l6}\textrm{cm}^2$으로 계산되었다. 운전압력 500 mTorr 이하의 영역에서 절연파괴 전기장의 세기는 약 $5.7\times10^4$V/m-Torr의 값을 갖으며 압력에 반비례하여 감소하였고, 500 mTorr에서 전기장은 12.5 kV/m로 최저 값을 갖고, 500 mTorr 이상의 영역에서는 약 43 V/m-Torr로 압력에 비례하여 증가하였다. OES 측정결과 마이크로파 공기 플라즈마에서 발생되는 주요 이온의 성분은 산소, 아르곤, 질소였으며, 특히 500 mTorr 이하의 영역에서는 산소와 아르곤 이온의 발생이 지배적이었다. 공기내의 산소(O(II))의 이온온도는 압력이 증가함에 따라 약 1.2 eV에서 0.5 eV로 감소하는 경향을 보였다. 정전 탐침 측정 결과는 500 mTorr 이하의 영역에서 플라즈마 밀도가 증가하는 경향을 보였으며 500 mTorr 이상의 영역에서 플라즈마 밀도는 비교적 낮았다.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.405-410
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• 2006

We fabricated gas sensors using carbon nanotubes (CNTs) as electron emitters for the purpose of detecting inert gases. By using the silicon-glass anodic bonding and glass patterning technologies with the typical Si process, we improved the compactness of the sensors and the reliability in process. The proposed sensor, based on, an electrical discharge theory known as Paschen's law in principle, works by figuring the variation of the discharge current depending on gas concentration. In the experiment, the initial breakdown characteristics were measured for air and Ar as a function of gas pressure. As the result, even though it should be realized that there are many other factors which have an effect on the breakdown of a gap, the sensors led to similar result as predicted by Paschen's law, and they showed a possibility as gas sensors which enable to detect the gas density ranged to the vacuum pressure from 1 to $10^{-3}$ Torr.

• 대한방사선기술학회지:방사선기술과학
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• 제2권1호
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• pp.71-83
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• 1979

Not only the insulating oil used for extra high voltage and high capacity transformer has a lot of possibilites of a corona discharge in oil, but the oil is easily degraded by a response of light oxidization. This study is either to classfy, with priority given to a transformer oil produced in Korea belonging to, the insulating oil No. 2, the sample irradiated the ultraviolet rays, treated a corona discharge in oil by a high voltage DC source and done nothing, or to measure the characteristics of breakdown, V-i, I-t and electrode material. The obtained results can be summarized as followings: (1) Unless the sample is contacted with the air, on the process to irradiate the ultraviolet rays, the sample less influence on the changes of the electric characteristics. At the same time, if the sample is contacted with the air and irradiated the ultraviolet rays, the sample shows a remarkable changes of the electric characteristics, and a declined breakdown strength. This tells us that the influence of the light irradiation must be considered as a primary factor of degrading the insulating oil. (2) In the oil treated by a corona discharge, breakdown voltage is declined more than in the oil not to be treated with it. This means that the degradation of the insulating oil is getting increased by a corona discharge in oil. (3) It shows that the increase of conducting current has little to do with breakdown voltage. (4) The conducting current depending on the electrode materials can be put in order by value as Al>Cu>Fe. This is due to the differences of the work function of each metals, and an chemical reaction with the insulating oil. These result can be a great help in verifying the degradation progress of the insulating oil and furnish a new technical information to the manufacturers of the insulating oil and electrical equipment designers and operators. Besides, this study would be helpful to improve the electrical characteristics of the insulating oil produced in Korea.

• 조명전기설비학회논문지
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• 제13권4호
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• pp.87-95
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• 1999

새로운 종류의 고체상태 대전력, 고속전자장치 즉 광전도전력스위치(PCPS)의 가장 큰 문제점은 평균전계하의 표면에서 스위치 섬락의 대부분이 반도체의 벌크파괴보다 낮다는 것이다. 이러한 문제를 극복하고 고밀도 고체 전력 스위치에 사용할 수 있는 유일한 방법이 고체 절연물로 표면을 페시베이션(Passivation)하는 것이다. 본 실험에서 Silicon의 절연내력은 진공중에서 10[kV/cm]에서 심하게 열화되어졌고, 기중에서 30[kV/cm], SF6에서 80∼90[kV/cm]으로 개선되지만, 스위치의 주 응용이 진공 또는 우주에서 사용되기 때문에 이러한 현상은 매우 심각한 문제이다. 페시베이션후 소자들은 진공과 기중에서 언페시베이션된 소자가 SF6내에서 얻을 수 있는 만큼의 높은 파괴값을 가졌다. 이러한 결과로 볼 때 페시베이션된 소자들이 매우 우수한 파괴값을 가진다는 것을 알 수 있다. 본 논문은 고전계 하에서 페시베이션 전·후 실리콘 파괴의 주 특성과 메커니즘에 대해 밝혔다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.185-188
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• 2002

In the design of superconducting power equipments such as transformer, cable and fault current limit, knowledge of the dielectric behavior of both liquid and gaseous at very low temperatures is very importance. Especially, Electrical properties of liquid nitrogen($LN_{2}$) and gaseous nitrogen($GN_{2}$) have become of great interest again since the discovery of high temperature superconductors. However, many sources of $LN_{2}$and $GN_{2}$ problems in the test of pancake coil model arising form the deficiency of insulation data. Therefore, this paper describes the results of an experimental study on the ac breakdown voltage($V_{B}$) properties of $LN_2$ and Air under the electrode of simulated HTS pancake coil. The ac breakdown voltage of $GN_{2}$ have been measured by pancake coil-pancake coil gaps over the temperature range of 293 K to 77 K.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.361-366
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• 2005

In this paper, a modified multimode hem antenna is designed to have 142 mm horn aperture radius and 921 mm length in order to be safe under 100 MW peak pulse power at 3 cm wave length through breakdown phenomenon study that threshold field strengths for the air breakdown phenomena is decided to be 3.78 MV/m. The proposed antenna is measured gain over 27 dBi and the -25 dB beam width of 29$^{\circ}$ in vertical plane.

• 한국초전도ㆍ저온공학회논문지
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• 제6권1호
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• pp.22-27
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• 2004

It is important to mechanical properties of dielectric paper and cable to optimum electrical insulation design of HTS cable, because the cable has experience of mechanical stress, such as tensile stress, bending stress. Also, it is operated at cryogenic temperature. From the results, it was observed that the tensile strength of PPLP in liquid nitrogen was high more than that of air, but tensile strain decrease sharply. According as tensile strength increases, the breakdown stress of PPLP in liquid nitrogen is decreased. Because PPLP was deteriorated by microcrack and tensile strain. According as bending radius multiple is decrease, the ac and impulse breakdown stress of mini-model cable is sharply decreased.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
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• pp.61-64
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• 2003

The degradation of the dielectric properties of insulating papers that were used under loaded conditions at cryogenic temperature was paid attention. Electrical and tensile stress properties of dielectric paper at cryogenic temperature have been investigated to optimum insulating design of high-Tc superconducting(HTS) cable. Tensile strength of PPLP in liquid nitrogen was high more than that of air, but tensile strain could know that decrease sharply. According as tensile strength increases, the breakdown stress of PPLP in liquid nitrogen was decreased.