• 조명전기설비학회논문지
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• 제26권4호
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• pp.41-47
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• 2012

This paper deals with the electrical characteristics related to power loss, equivalent resistance, and leakage currents flowing through new and deteriorated zinc oxide(ZnO) arrester elements subjected to the mixed DC and 60[Hz] AC voltages. The test specimens were deteriorated by 8/20[${\mu}s$] impulse current of 2.5[kA]. The leakage current-applied voltage($I-V$) characteristic curves of ZnO surge arrester elements were measured as a parameter of the ratio of the peak of 60[Hz] AC voltage to the peak of total voltage. As a consequence of test results, in case of the same applied voltage, the leakage currents flowing through the deteriorated ZnO arrester elements were higher than those flowing through the new ZnO surge arrester elements. The cross-over phenomenon in $I-V$ curves of ZnO surge arrester elements measured as a parameter of the mixed ratio of DC and AC voltages was observed at the low current domain. The effect of DC voltage on the leakage current flowing through ZnO surge arrester elements is pronounced at the same magnitude of test voltages. In addition, the larger the applied number of 8/20[${\mu}s$] impulse current of 2.5[kA] is, the greater the power loss is, in particular, the more severe the power loss increases at higher applied voltages.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.283-285
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• 1987

Transient conduction current (I - t characteristics) were measured in thin PPMMA (plasma-polymerized methyl methacrylate) films over the temperature range $60^{\circ}C-140^{\circ}C$ and the applied voltage range 3V - 30V. The current, which increased with temperature rise at constant applied voltage, showed less absorption current (current decay with time) at higher temperature region compared with those at lower temperature region. And the current, which increased with applied voltage rise at the constant temperature, showed less absorption current at higher voltage compared with those at lower voltage. The electric field current density characteristic curves were abtained from the conduction current values were after applying voltage for 30 minutes. And transient conduction currents were analyzed with high field conduction theories.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권8호
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• pp.396-402
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• 2006

Even the case DC circuit Breaker have good quality for interruption of high current like heavy load current, short-circuit current, the verification for small current breaking capability of circuit breaker should be performed. It comes from the reason DC small current breaking failure can be lead to break out second heavy fault condition and in the long run substation shutdown. In this paper, we can find the characteristics of DC small current and international test standard discription about small current breaking and one of the proper solution to get over it.

• Transactions on Electrical and Electronic Materials
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• 제16권1호
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• pp.37-41
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• 2015

The most common structure of the current transformer (CT) consists of a length of wire wrapped many times around a silicon steel ring passed over the circuit being measured. Therefore, the primary circuit of CT consists of a single turn of the conductor, with a secondary circuit of many tens or hundreds of turns. The primary winding may be a permanent part of the current transformer, with a heavy copper bar to carry the current through the magnetic core. However, when the large current flows into a wire, it is difficult to measure its magnitude of current because the core is saturated and the core shows magnetic nonlinear characteristics. Therefore, we proposed a newly designed CT which has an air gap in the core to decrease the generated magnetic flux. Adding the air gap in the magnetic path increases the total magnetic reluctance against the same magnetic motive force (MMF). Using a ferrite core instead of steel also causes the generation of low magnetic flux. These features can protect the magnetic saturation of the CT core compared with the steel core. This technique can help the design of the CT to obtain a special shape and size.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권1호
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• pp.23-29
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• 2005

This paper presents the characteristics of leakage currents flowing through ZinC Oxide(ZnO) surge arrester blocks under mixed direct and 60 Hz alternating voltages. A mixed voltage, in which an alternating voltage is superimposed upon a direct voltage, appears on the HVDC system network. The mixed direct and alternating voltage generator with a peak open-circuit of 10 kV was designed and fabricated. The leakage currents and V-I curves for the fine and used ZnO surge arrester blocks were measured as a function of the voltage ratio k, where the voltage ratio k is defined as the ratio of the peak of alternating voltage to the peak of the mixed voltages. The resistive component in the leakage current in the low conduction region is significantly increased with increasing the voltage ratio k. The V-I characteristic curves for the mixed voltages lies between the direct and alternating characteristics, and the cross-over phenomenon in the high conduction region was appeared.

• Wind and Structures
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• 제3권3호
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• pp.143-158
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• 2000

This report presents the findings of a one-year monitoring effort to empirically characterize and evaluate the nature of near-ground winds for structural engineering purposes. The current wind engineering practice in the United States does not explicitly consider certain important near-ground wind characteristics in typical rough terrain conditions and the possible effect on efficient design of low-rise structures, such as homes and other light-frame buildings that comprise most of the building population. Therefore, near ground wind data was collected for the purpose of comparing actual near-ground wind characteristics to the current U.S. wind engineering practice. The study provides data depicting variability of wind speeds, wind velocity profiles for a major thunderstorm event and a northeaster, and the influence of thunderstorms on annual extreme wind speeds at various heights above ground in a typical rough environment. Data showing the decrease in the power law exponent with increasing wind speed is also presented. It is demonstrated that near-ground wind speeds (i.e., less than 10 m above ground) are likely to be over-estimated in the current design practice by as much as 20 percent which may result in wind load over-estimate of about 50% for low-rise buildings in typical rough terrain. The importance of thunderstorm wind profiles on determination of design wind speeds and building loads (particularly for buildings substantially taller than 10 m) is also discussed. Recommendations are given for possible improvements to the current design practice in the United States with respect to low-rise buildings in rough terrain and for the need to study the impact of thunderstorm gust profile shapes on extreme value wind speed estimates and building loads.

• 마이크로전자및패키징학회지
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• 제20권4호
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• pp.53-58
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• 2013

An innovative packaging solution, Flip Chip with Copper (Cu) Column bond on lead (BOL) Enhanced Process (fcCuBE$^{(R)}$) delivers a cost effective, high performance packaging solution over typical bond on capture pad (BOC) technology. These advantages include improved routing efficiency on the substrate top layer thus allowing conversion functionality; furthermore, package cost is lowered by means of reduced substrate layer count and removal of solder on pad (SOP). On the other hand, as electronic packaging technology develops to meet the miniaturization trend from consumer demand, reliability testing will become an important issue in advanced technology area. In particular, electromigration (EM) of flip chip bumps is an increasing reliability concern in the manufacturing of integrated circuit (IC) components and electronic systems. This paper presents the results on EM characteristics on BOL and BOC structures under electrical current stressing in order to investigate the comparison between two different typed structures. EM data was collected for over 7000 hours under accelerated conditions (temperatures: $125^{\circ}C$, $135^{\circ}C$, and $150^{\circ}C$ and stress current: 300 mA, 400 mA, and 500 mA). All samples have been tested without any failures, however, we attempted to find morphologies induced by EM effects through cross-sectional analysis and investigated the interfacial reaction characteristics between BOL and BOC structures under current stressing. EM damage was observed at the solder joint of BOC structure but the BOL structure did not show any damage from the effects of EM. The EM data indicates that the fcCuBE$^{(R)}$ BOL Cu column bump provides a significantly better EM reliability.

• 전기학회논문지
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• 제56권10호
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• pp.1791-1795
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• 2007

Small ions generated at conductor corona sources remain in the atmosphere until they recombine with ions of opposite polarity, attach to aerosols, or make contact with an object. Ion current density is major factor to design conductor configuration of DC overhead transmission line. Several techniques have been used to measure the ion current of HVDC overhead transmission line. In this study, the ion current density was measured by a plate electrode made of a metal flat board at DC corona cage. The sensitivity of the plate electrode is $0.156uA/m^2/V$. To obtain an useful database on corona discharge, it is necessary to do corona test on several kinds of conductor bundles. Therefore, a number of experiments were conducted on several kinds of conductor bundles. To reliably analyze ion effects, corona cage test data were obtained over a long period of time under various weather conditions and expressed as a statistical distribution. Ion current density distribution in foul weather shows a significant increase in levels over the corresponding fair weather. Based on this results, we evaluated the environmental characteristic caused by ion flow of three candidated conductor bundles.

• 대한수의학회지
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• 제31권1호
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• pp.33-40
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• 1991

For the observations of both the membrane properties and the excitability on the unfertilized eggs of female mice, changes of the membrane resistance and the membrane potential by hyerpolarizing current stimulation were recorded. As current-voltage relation was linear over the entire range (-180mV~+60mV), membrane resistance($R_m$) was calculated from the amplitude of electrotonic potential to a given stimulus current. Also the presence of anode-break excitation was confirmed. The results were as follows; 1. There was a linear relation between the membrane resistance and resting membrane potential, the expected input resistance was 61. 4M$\Omega$(resting membrane potential was $-18.9{\pm}8.7mV$, mean${\pm}$SD, n=30). 2. Transient depolarization with overshoot was generated just after hyperpolarizing current stimulus and showed the dependency of stimulus duration. 3. Transient depolarization lasted over 30ms, amplitude of these depolarization was increased by high $Ca^{{+}{+}}$(20mM) and inhibited by $Ca^{{+}{+}}$-antagonist, $Mn^{{+}{+}}$. 4. From the above results, it was suggested that the unfertilized mouse egg showed the characteristics of the excitable cell.

• 한국안전학회지
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• 제38권4호
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• pp.8-14
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• 2023

This study presents the characteristics of short circuits (SCs) caused by excessive currents in high-voltage cables used in electric vehicles and emphasizes the need to calculate the cross-sectional areas of these cables according to the SC current. Three direct current power supplies were connected in parallel to test the SC characteristics caused by excessive currents, and a timer and a magnetic contactor were used to deliver the conduction time and SC current. A circular infrared-radiation heater was used to test the temperature-dependent SC characteristics, a thermocouple was used to measure the temperature, and a shunt resistor was used to measure the current. As the SC current increased, the fusing time of the cable decreased. Additionally, a high-voltage cable (with an area of 16 mm² ) used in electric vehicles fused when a current (approximately equal to 55 times the allowable current) flowed for 0.2 s (operating time of the protective device). When the SC current is 10 kA, the cable may fuse during the operating time of the protective device, thus creating a fire hazard. In electric vehicles, the size of the SC current increases in proportion to the capacity of the battery. Thus, the cross-sectional areas of the cables used should be calculated accordingly, and cable operations should be properly coordinated with the surrounding protective devices.