• 전기학회논문지
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• 제56권4호
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• pp.669-676
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• 2007

This paper presents a new power flow method to analyze the AC electric railway system effectively in both cases of traction and regenerative braking of the trains. The algorithm to easily solve the power flow of the AC electric railway system with the trains of regenerative braking from the system without a train of regenerative braking is derived. Using this new power flow method, the voltage characteristics of a typical AC electric railway system is easily analyzed in both cases of traction and regenerative braking of the trains. We show that the presented method can be applied effectively in order to analyze the AT-fed AC electric railway system in both cases of traction and regenerative braking of the trains. A STATCOM(Static Synchronous Compensator) is applied to the system in order to improve the voltage drop problem and this case is also analyzed to show the effect of STATCOM.

• 전력전자학회논문지
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• 제21권1호
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• pp.80-87
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• 2016

This study investigates output voltage variation of a voltage disturbance generator in case of sag and swell modes. The generator uses series transformers and silicon-controlled rectifier thyristors to provide voltage disturbance; consequently, voltage drop at the output terminal is inevitable. On the basis of the analysis, voltage drop increases as the power factor decreases in lagging. Voltage drop is 3.7 [%] at a power factor (lagging) of 0.8. Simulation and experimental results show the validity of the analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전력기술부문
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• pp.337-339
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• 2005

The purpose of this paper is to compensate the voltage drop of the power system in the AC High-Speed Railway (HSR). Reactive power compensation is often the most effective way to improve system voltage drop. The suitable modeling of the electric railway system should be applied to the EMTP. the dynamic characteristics of 3-Phase Induction Motor in Electric Railway Systems is considered for precise modeling. it is shown through EMTP simulation that voltage drop can be compensated effectively by STATCOM.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.63-68
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• 2004

Recently ER fluids are put to practical use in fluid power industry field. As only with electrical signal change to the valve in which ER fluid flowing, ER fluid flow is controlled, so devepment of simple ER valves have been tried. In this case a technical problem is to check the pressure drop caused from flow rate change in valves because the pressure drop is very small. In this study ER valves are designed and manufactured, and small pressure drop induced from flow rate change is checked by pressure transducer which is made with appling strain gage. The ER valves and pressure drop check method are considered to be applied to the fluid power industry.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3892-3901
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• 2021

The pressure drop of a moisture separator in a steam generator is the important design parameter to ensure the successful performance of a nuclear power plant. The moisture separators have a wide range of operating conditions based on the arrangement of them. The prediction of the pressure drop in a moisture separator is challenging due to the complexity of the multi-dimensional two-phase vortex flow. In this study, the moisture separator test facility using the air/water two-phase flow was used to predict the pressure drop of a moisture separator in a Korean OPR-1000 reactor. The prototypical steam/water two-phase flow conditions in a steam generator were simulated as air/water two-phase flow conditions by preserving the centrifugal force and vapor quality. A series of experiments were carried out to investigate the effect of hydraulic characteristics such as the quality and liquid mass flux on the two-phase pressure drop. A new prediction model based on the scaling law was suggested and validated experimentally using the full and half scale of separators. The suggested prediction model showed good agreement with the steam/water experimental results, and it can be extended to predict the steam/water two-phase pressure drop for moisture separators.

• 전기학회논문지
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• 제63권7호
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• pp.1013-1018
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• 2014

This paper described the development of equalizing spacer for minimization of voltage drop according to DC feeder extension. Power consumption is increased as shorter interval of train driving time and transportation capacity increase in urban subway. Therefore we investigated voltage drop of catenary at a point in case of traction driving of a train in parallel to the DC power supply system. Based on it's result, equalizing spacer is designed and fabrication to minimize the voltage drop in accordance with the power supply line arranged in three rows, and then its performance was confirmed that the stress distribution of main body and the distributed load are satisfied through the body structure modeling.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.289-291
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• 2001

This paper represents the application of the Static Var Compensator (SVC) on the electric railway power supply system to compensate for the voltage drop. The high reactance of line and a heavy train load consume a significant amount of the reactive power which results the voltage drop. This paper shows that the SVC is necessary for voltage compensation in the railway power supply system and verify effectiveness of the SVC through the simulation by using PSCAD/EMTDC. In this paper, the case studies were performed with the various line length and train loads.

• 한국산업융합학회 논문집
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• 제26권6_1호
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• pp.985-991
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• 2023

This study proposes a solution to the voltage drop in electric vehicle chargers, due to the parasitic resistance and inductance of power cables when the chargers are separated by large distances. A method using multi-level electric vehicle chargers that can output power in stages, without installing an additional energy supply source such as a reactive power compensator or an energy storage system, is proposed. The voltage drop over the power cables, to optimize the charging scheduling, is derived. The obtained voltage drop equation is used to formulate the constraints of the optimization process. To validate the effectiveness of the obtained results, an optimal charging scheduling is performed for each period in a case study based on the assumed charging demands of three connected chargers. From the calculations, the proposed method was found to generate an annual profit of $20,800 for a $12,500 increase in installation costs.

• 전력전자학회논문지
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• 제13권3호
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• pp.213-220
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• 2008

본 논문에서는 전압강하 보상모드를 갖는 직류 지하철 회생인버터 시스템을 제안하였다. 주 정류기에 고장이 발생하면 직류 지하철은 전원측으로부터 전력을 공급받지 못한다. 실제적으로 사고를 방지하기 위하여 변전소 측에 예비 정류기가 설치되어 있다. 이 논문에서는 전압강하 보상모드가 별도의 예비정류기를 대신하여 회생인버터에 부가된다. 제안된 인버터 시스템은 직류 가선 전압에서 발생한 회생에너지를 계통으로 반환한다. 부가하여, 인버터는 직류 지하철 시스템에서 사용된 전력변환장치에 의하여 야기된 고조파를 보상할 수 있다. 컴퓨터 시뮬레이션에 의해서 제안된 제어 알고리즘의 효용성을 설명하였다.

• 대한안전경영과학회지
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• 제17권4호
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• pp.397-401
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• 2015

In this study, analysed the characteristics of power drop and surface damage in solar cell through high temperature and humidity test in the 3 case of EVA(ethylene vinyl acetate) and 2 case ribbon thickness. The solar cells were tested during the 500hr in $85^{\circ}C$ temperature and 85% relative humidity conditions, that excerpted standard of PV Module(KS C IEC-61215). Through the EL(Electroluminescence) shots, specimen's surface have partialy damaged. Before and after high humidity and high temperature test, ribbon thickness $200{\mu}m$ EVA1 case power drop rate was 8.463%, EVA2 case was 6.667%, EVA3 case was 6.373%. In the ribbon thickness $250{\mu}m$ EVA1 case power drop rate was 6.521%, EVA2 case was 8.517%, EVA3 case was 6.019%. EVA3 case was the lowest power and FF(fill factor) drop rate at the 2 case of ribbon thickness, because EVA3 is laerger than EVA1 and EVA2 in thickness, elongation and tensile strength.