• 조명전기설비학회논문지
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• 제22권10호
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• pp.8-17
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• 2008

본 논문에서는 선박용 HID조명의 방전 개시전압을 조절함으로써 초기 방전전류를 억제하여, HID조명의 안정적인 점등이 가능한 제어방식을 제안하였다. 제안된 제어 방식은 방전 대기전압까지 출력전압을 상승시킨 후, 충전전압의 저항부하 방전을 통하여 전압을 감소시키면서, 설계된 방전개시전압시점에서 이그니터를 점화하여 방전 개시 전류를 제한한다. 방전 후 정상상태에서는 정전류 제어로 조도를 제어하게 된다. 제안된 방식은 별도의 전압제어기를 포함하지 않으면서도, 방전개시 시점을 조절할 수 있으므로, 초기 방전 전류를 크게 제한할 수 있으므로, 안정적인 점등과 조명의 수명을 확대할 수 있는 장점이 있다. 또한 조명의 이상상태를 간단한 이상검출 회로를 통하여 순시적으로 감시하여 전체 시스템의 보호 성능을 개선하였다. 제안된 제어기는 실제 선박용 2.5[kW]급의 HID 탐사조명에 대한 실험을 통하여 검증하였다.

• Journal of Electrical Engineering and Technology
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• 제11권2호
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• pp.436-444
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• 2016

Oil-paper insulation of valve-side windings in converter transformers withstand electrical stresses combining with AC, DC and strong harmonic components. This paper presents the physical mechanisms and experimental researches on partial discharge (PD) of oil-paper insulation at pulsating DC voltage. Theoretical analysis showed that the phase-resolved distributions of PDs generated from different insulated models varied as the increase of the applied voltages following a certain rule. Four artificial insulation defect models were designed to generate PD signals at pulsating DC voltages. Theoretical statements and experimental results show that the PD pulses first appear at the maximum value of the applied pulsating DC voltage, and the resolved PD phase distribution became wider as the applied voltage increased. The PD phase-resolved distributions generated from the different discharge models are also different in the phase-resolved distributions and development progress. It implies that the theoretical analysis is suitable for interpretation of PD at pulsating DC voltage.

• Applied Science and Convergence Technology
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• 제27권2호
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• pp.23-25
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• 2018

With respect to the electrode structure and the discharge characteristics, the atmospheric pressure plasma sheet of a thin polyimide film is introduced in this study; here, the flexible plasma device of a dielectric-barrier discharge with the ground electrode and the high-voltage electrode formulated on each surface of a polyimide film whose thickness is approximately $100{\mu}m$, that is operated with a sinusoidal voltage at a frequency of 25 kHz and a low voltage from 1 kV to 2 kV is used. The streamer discharge is appeared along the cross-sectional boundary line between two electrodes at the ignition stage, and the plasma is diffused on the dielectric-layer surface over the high-voltage electrode. In the development of a plasma sheet with thin dielectric films, the avoidance of the insulation breakdown and the reduction of the leakage current have a direct influence on the low-voltage operation.

• 조명전기설비학회논문지
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• 제24권10호
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• pp.99-105
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• 2010

This paper discussed the theoretical simulation results for developing the blumlein pulsed power source and showed the circuit configuration and the discharge characteristics of the realistic manufactured pulsed power system. In the simulation, the output voltage characteristics at a load resistor showed the general impulse shape when the impedance of a single coaxial cable is matched with the that of a load resistor. In addition, it is confirmed that output values of the pulsed power can be easily controlled by the duplication of coaxial cables and the pulsed waveform showed the general impulse characteristics. Specifically, the inception discharge voltage in the gap distance of 5[mm] between needle and plane electrodes is about 20[kV] and which is lower than about 29[kV] in 9[mm] due to the difference of the reaching time of the inception voltage. Therefore, this paper showed that the output voltage of the blumlein pulsed power source can be easily controlled.

• 전기학회논문지P
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• 제53권3호
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• pp.148-151
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• 2004

For turn on high pressure sodium vapor lamp, Starting Voltage is very important factor. This starting voltage supply to high pressure sodium vapor lamp as electric discharge lamp, Electric field is producted in electric discharge tube, So accelerative electron collide against vapor atom and second electron is generated, And rapidly the current flow to electric discharge tube. This starting voltage is high voltage and source for melting contact that relay is according as turn on/off high pressure sodium vapor lamp. Consequently, This paper propose that the prevention of melting contact in accordance relay of controller for turn on/off high pressure sodium vapor lamp.

• 센서학회지
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• 제30권2호
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• pp.105-108
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• 2021

Detection and localization of partial discharge are considered critical techniques for estimating the lifetimes of power cables. High-frequency current transformers (HFCTs) are commonly used for the detection of partial discharge in high-voltage alternating current (HVAC) power cables; however, their applicability is compromised by the limitations of the installation locations. HFCTs are typically installed in cable terminals or insulation joint boxes because HVACs induce strong time-varying magnetic fields around the cables, saturating the ferromagnetic materials in the HFCTs. Therefore, partial discharges near the installation locations can be detected. In this study, the feasibility of partial discharge detection using a HFCT was investigated for high-voltage direct current (HVDC) cables. We demonstrated that the HFCT could be installed at any location in the HVDC power cable to monitor partial discharge along the entire cable length. Furthermore, we showed that the HFCT could detect the location of partial discharge with high accuracy.

• Environmental Engineering Research
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• 제10권3호
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• pp.144-154
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• 2005

The use of ozone gained acceptance in the production of ultrapure water because of its powerful oxidizing ability. Ozone is currently used to deactivate microorganisms and remove organic contaminants. However, interest also exists in using radical species, which arc stronger oxidants than ozone, in such processes. One means of producing radical species is by corona discharge. This work investigates the use of a novel pulseless corona-discharge system for the removal of organic substances in ultrapure water production. The method combines corona discharge with electrohydrodynamic spraying of oxygen, forming microbubbles. Experimental results show that pulseless corona discharge effectively removes organics, such as phenol and methylene blue, in deionized water. The corona-discharge method is demonstrated to be comparable to the direct use of ozone at a high-applied voltage. The results also show that a minimum applied voltage exists for operation of the corona-discharge method. In this work, the minimum applied voltage is approximately 4.5 kV. The kinetic rate or phenol degradation in the reactor is modeled. Modeling results show that the dominant species of the pulseless corona-discharge reactor are hydroxyl radical and aqueous electron. Several radical species produced in the pulseless corona-discharge process are identified experimentally. The. major species are hydroxyl radical, atomic hydrogen species, and ozone.

• 한국대기환경학회지
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• 제18권5호
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• pp.337-344
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• 2002

In this study, we analyzed the NO removal efficiency by the pulsed corona discharge process and investigated the effects of several process variables such as initial concentrations of NO, $H_2O$, and NH$_3$, applied voltage, pulse frequency, diameter of the discharge electrode, and residence time. The removal efficiency of NO increased by the addition of $H_2O$ or NH$_3$, but the changes of initial NH$_3$ and $H_2O$ concentrations did not affect the removal efficiency of NO significantly. With the increases of the applied voltage or the residence time, the removal efficiency of NO increased. In addition, with the increases of the pulse frequency of applied voltage, or the diameter of the discharge electrode, the removal efficiency of NO increased. The experimental results can be used as a basis to design the pulsed corona discharge process to remove NO$_{x}$, SO$_{x}$ and VOCs.OCs.

• 한국자동차공학회논문집
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• 제4권1호
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• pp.123-133
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• 1996

From the experimental study of wire-cut Electric Discharge Machining of alloyed tool steel and tungsten carbide, the characteristics such as cutting speed, surface roughness has been observed and evaluated for various conditions. Cutting speed is improved as peak discharge current and wire tension become increased, and gap voltage and spark cycle decreased. Surface roughness can be better when peak discharge current and gap voltage become smaller, or spark cycle and wire tension become larger. Secondary cut is recommended to obtain high precision and good quality.

• E2M - 전기 전자와 첨단 소재
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• 제9권9호
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• pp.942-948
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• 1996

Electrical properties such as surface flashover discharge and discharge degradations of insulating materials for superconducting cable have been investigated. It is found that the surface voltage is proportional to $l^{0.7}$ (l: discharge length) in liquid helium (LHe). V-t characteristic in LHe was a n=5.5 that was less than liquid nitrogen (L $N_{2}$). After applied AC voltage, the surface condition of polymer films was observed non-eroded areas and eroded areas. The eroded area is depending on the applied voltage. In case of LHe, the crack was observed.d.