• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1867-1869
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• 1999

Pulse electric field induced electron emission from ferroelectrics has been studied with Pb$(Zr_xTi_{1-x})O_3$ ceramics with varying Zr/Ti ratio from 35/65 to 65/35, Electron emission was proved to be concentrated on the electrode edge by emission profile test and emission capture photographs. The 65/35 composition showed largest emission charge in lowest field and lowest emission threshold field. The emission characteristics are closely dependent on their ferroelectric properties in hysteresis curve. Electron emission charge increases with the polarization charge and emission threshold voltage is dependent on coercive field regardless of their composition. But dielectric constant has little relation with emission property. Electron emission charge increases exponentially with pulse electric field irrespective of composition. On the assumption that the surface potential is linear with the pulse electric field, electron emission can be regarded as a field emission at the electrode edge using Fowler-Nordheim plot of ln$(Q_e/E_{fe})$ to $1/E_{fe}$.

• 조명전기설비학회논문지
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• 제25권8호
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• pp.39-47
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• 2011

The motion of a conductive spherical particle under uniform electric field is investigated in order to find a suitable method for removing the conducting solid impurities contained in liquid plastic. When the positive dc voltage applied to the upper electrode, the vertical up-and-down motion of a charged particle by electrostatic force is observed by a charge-coupled device (CCD) camera or a high-speed video camera. The experimental data of the static threshold voltage by which the particle starts to move toward the counter electrode in air or silicone oil are in good agreement with theoretical value. When the applied voltage is larger than the static threshold voltage, the particle motion pattern in silicone oil consists of four stages: upward motion, stopping at the upper electrode, downward motion and stopping at the lower electrode. The stopping motion on the electrode is thought to be caused by the liquid flow accompanied by the particle motion. The particle charge calculated by integrating the pulse current, which is generated by the charge exchange between the electrode and the particle, is approximately 0.1~0.25 times of the theoretical value. This study is expected to help understand the electric properties of microparticles in oil circuit breaker (OCB) and oil transformer and improve their performance and longevity.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권2호
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• pp.171-178
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• 2013

This paper discusses to conduct experimental verification of two types of micro electric vehicles (EV) in order to realize improvement in electric mileage and shorten a charging time of the battery. First, electric double layer capacitor (EDLC) systems to use as a secondary battery are proposed. The internal resistance of EDLC is small compared with a rechargeable battery, and it is suitable for momentary charge-discharge of EV. Next, control circuits of the capacitors to increase the regenerative electric power are utilized. Then, a novel method to charge a main battery of the EV is introduced. Finally, experimental results demonstrate the validity of the proposed method.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.184-187
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• 2005

SUS 304 발열선(직경 2.3mil)과 $Zr-KClO_4$ 기폭화약을 사용한 전기식 착화기에 대한 열특성을 시험하고 Fitted Wire Model로 분석한 결과, 약 $300^{\circ}C$ 부근에서 기폭화약과 관련된 열특성 파라미터가 급격하게 변화되었다. 이 현상은 기폭화약에 사용된 $KClO_4$의 상변화로 인한 흡열과 발열선과 기폭화약 계면의 물리적 변화로 발생된 것으로 판단되며, 결과로 열특성 시험으로 구한 파라미터가 유용한 온도 범위를 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 C
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• pp.1494-1495
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• 2006

A complete finite element analysis method for discharge onset process, which is governed and coupled by charge transport equation and electric field equation, was presented. The charge transport equation of first order was transformed into a second-order one by utilizing the artificial diffusion scheme. The two second-order equations were analyzed by the finite element formulation which is well-developed for second-order ones. The Fowler-Nordheim injection boundary condition was adopted for charge transport equation. After verifying the numerical results by comparing to the analytic solutions using parallel plane electrodes with one carrier system, we extended the result to blade-plane electrodes in 2D xy geometry with three carriers system. Radius of the sharp tip was taken to be 50 ${\mu}m$. When this sharp geometry was solved by utilizing the space discretizing methods, the very sharp tip was found to cause a singularity in electric field and space charge distribution around the tip. To avoid these numerical difficulties in the FEM, finer meshes, a higher order shape function, and artificial diffusion scheme were employed.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1376-1383
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• 2004

In the present work, a series of experiments have been performed on electro-hydrodynamic atomization of non-conducting liquid using a charge injection type nozzle. Effects of liquid flow rate, input voltage, and distance between the needle and the ground electrode (nozzle-embedded metal plate) have been examined. For fixed electrode distances, total and spray currents increase with the increase of liquid flow rate and input voltage. When the distance between the needle tip and the ground electrode becomes closer, the total, leakage and spray currents increase, while the onset voltage for the dielectric breakdown decreases. When the electric field strength of the liquid jet exceeds that for the air breakdown, a portion of the electric charges in the liquid jet is dissipated into the ambient air, and the charge density shows a limiting value. Atomization quality can be improved by increasing the liquid flow rate due to the higher charge density and the enhanced aerodynamic effect.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.392-394
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• 2002

Yoke simulator has been made for understanding beam movements in the deflection fields of the CRT. Consisting of the modeler, solver and post-processor, the simulator makes yoke model (conventional and rectangular yoke) and calculates charge sources and magnetic filed by BEM (boundary element method). This system supports a number of charge elements (line and surface charges) and beam movements can be predicted by the system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2117-2119
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• 1999

In this paper, the electric fields inside GIS with metal impurity is analysed by the use of 3 dimensional Surface Charge Method. We find the metal impurity makes electric field distribution inside GIS non-uniform and causes breakdown of $SF_6$ gas in GIS.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 C
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• pp.1192-1194
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• 1998

This paper presents a optimal operation algorithm of 1MW class Battery Energy Storage System (BESS) which is constructed in EHWA electric corporation. Total electric charge of conventional '97 year and simulated '98 year are compared to verify the validity of the proposed algorithm. Simulation results have showed that the about \\32,000,000 reduction of electric charge for 1 year.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1987-1989
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• 2000

In this paper, electric field distribution of dielectric sphere considering surface or volume resistivity is analysed by the use of rotational symmetric charge simulation method. We applied three methods such as ${\alpha},{\beta}$ modified $\beta$ method to check electric field calculation error. We find f method and modified $\beta$ method are suitable to simulate volume and surface resistivity respectively.