• 한국철도학회논문집
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• 제9권4호
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• pp.504-509
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• 2006

Currently, most of TDIS(Train Destination Indicator System) is operated colored-LED type equipment in Korea. This current LED type TDIS equipment has not graceful display and causes passenger's fatigues because of the LED module inherent characteristics as a display light source, high power consumption, high operating and maintenance costs, and et al. To address these several, we are developed new colored-LCD type TDIS equipment. According to our developed new TDIS equipment, we can achieve high resolution and graceful color stone of information display. Thus high graded service are able to provide to passengers. In addition, LCD module decreases power consumption, and it can be used permanently by changing only backlight in comparison with conventional equipment. Therefore we can decrease the maintenance cost and extend durability-period of TDIS equipment using new equipment.

• Journal of Power Electronics
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• 제16권2호
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• pp.685-694
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• 2016

This paper presents a reliability assessment model for the power semiconductors used in wind turbine power converters. In this study, the thermal loadings at different timescales of wind speed are considered. First, in order to address the influence of long-term thermal cycling caused by variations in wind speed, the power converter operation state is partitioned into different phases in terms of average wind speed and wind turbulence. Therefore, the contributions can be considered separately. Then, in regards to the reliability assessment caused by short-term thermal cycling, the wind profile is converted to a wind speed distribution, and the contribution of different wind speeds to the final failure rate is accumulated. Finally, the reliability of an actual power converter semiconductor for a 2.5 MW wind turbine is assessed, and the failure rates induced by different timescale thermal behavior patterns are compared. The effects of various parameters such as cut-in, rated, cut-out wind speed on the failure rate of power devices are also analyzed based on the proposed model.

• Transactions on Electrical and Electronic Materials
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• 제13권3호
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• pp.116-120
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• 2012

In this paper, ZnO-Epoxy nanocomposites (NEP) were prepared and epoxy composites that contain 5 wt% micro ZnO (MEP) and deliberately not well dispersed nano ZnO (NDNEP) were also prepared for purpose of comparison. The effects of the particle size and dispersion of ZnO on dielectric properties of epoxy resin were chiefly studied. Test results showed that: at a loading of 5 wt%, the three epoxy composites seem to have no significant difference on resistivity compared to epoxy resin; Dielectric constants of all the epoxy composites are also basically the same but they are bigger compared to that of the pure epoxy resin (unfilled); Dielectric dissipation factors ($tan{\delta}$) of NDNEP is greater than that of NEP and MEP. NEP has the minimum dielectric loss factor, whereas dielectric loss factors of the three epoxy composites are larger than that of the pure epoxy resin. The decreasing order of electrical breakdown strength for the three epoxy composites and for the pure epoxy resin is as follows: NEP>MEP>NDNEP>EP. Finally, in order to explain the experimental results the aggregation interface phase was proposed. Furthermore, addition of well dispersed nano filler has proved to have a positive effect on the improvement of the dielectric properties of epoxy resin.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.31-36
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• 2014

For decreasing an unexpected shutdown of Nuclear Power Plants, Korea Hydro & Nuclear Power co.(KHNP) has developed Single Point Vulnerability(SPV) of NPPs since 2008. SPV is the equipment that cause reactor shutdown & turbine trip or more than 50% power rundown due to its malfunction. New type Nuclear Power Plants need to develop the SPV list, so performed the SPV selection for about 1 year. To develop this, Failure Mode Effect Analysis(FMEA) methods are used. As results of FMEA analysis, about 700 equipment are selected as SPV. Thereafter those are going to be applied to new type Nuclear Power Plants to enhance equipment reliability.

• 전기학회논문지
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• 제63권2호
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• pp.297-305
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• 2014

Nowadays new water supply projects have been on the decline as the water-power constructions have saturated, which means that the existing power equipment have slowly aged and they require more efforts to maintain the system performance. An effective asset management method of power equipment has become a great necessity from both economical and technical aspects. To be balanced, the asset management should look into all three parts: management, engineering, and information. The purpose of this paper is to study a Risk-Based Maintenance (RBM) matrix method through the deterioration evaluation algorithm for an efficient reliability assessment of oil-immersed power transformers by considering both asset management and technical evaluation. Make use of this result, the equipment will be decided to be replace or repair otherwise on service.

• 유공압시스템학회논문집
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• 제6권1호
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• pp.25-31
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• 2009

This study presents an analytical model of hydraulic clutch system of a power shift transmission to analyze pressure modulation characteristics. A typical hydraulic clutch system was modeled by using AMESim in which the parameters of major components were measured for simulation. Test apparatus was established using the components of power shift and power shuttle clutches with instrumental equipment. The results of simulation and experiment were so close that the proposed analytical model in this study was validated. However the cylinder model analogized clutch dynamics need to be improved in future study. The effects of parameters of orifice diameter, accumulator stroke and oil temperature on pressure modulation were analyzed respectively. The results of parameter sensitivity analysis show that modulation time and set pressure can be easily adjusted by changing parameter values. It is also found that the hydraulic clutch system used in this study is so susceptible to oil temperature that cooling equipment is necessary.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 추계학술대회 논문집
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• pp.159-160
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• 2016

본 논문에서는 최근 건설기계용으로 연구되고 있는 E-TCS의 Power Electronics System에 대한 Topology와 제어방법을 제안한다. 디젤엔진과 같이 사용되는 E-TCS는 압축기와 터빈 그리고 요구되는 회전속도로 고속회전 및 발전이 가능한 모터와 이를 제어하는 인버터로 구성된다. 기존의 E-TCS를 위한 Power Electronics System의 경우 배터리의 전압강압으로 인버터의 전류량이 증가하여 Power Electronics System 및 모터의 Volume이 커지는 단점이 있으며, 특허가 존재하여 사용이 어렵다. 본 논문에서는 이와 같은 단점을 개선한 E-TCS를 위한 새로운 Topology 구성 및 제어방식을 제안한다.

• Journal of Power Electronics
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• 제12권4호
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• pp.519-527
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• 2012

A high step-down multiple-output LED driver is proposed in this paper. Firstly, the derivation of the driver with dual-output is presented and its operation principle and steady state performance are analyzed in detail. Secondly, a high step-down N-channel LED driver is proposed and its current auto-balance characteristic and step-down ratio are analyzed. Finally, an experimental prototype is built and the experimental results are given. The theoretical analysis and experimental results show that the proposed driver has the following virtues: First, if load balancing is achieved, the voltage gain is 1/N that of a Buck driver, where N is the number of channels. Second, each output automatically has an equal output current, without requiring more current close-loop control circuits than a Buck driver. Last, the voltage stresses of the switches and diodes are lower than those of a Buck driver, meaning that lower voltage switches and diodes can be used, and a higher efficiency can be expected.

• 한국철도학회논문집
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• 제10권2호
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• pp.96-102
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• 2007

This paper presents a study on the control of a power quality compensating equipment of electrical railway built in small-scaled to preliminary research. Because this compensating equipment is very complicated power electronics system, consisting of a scott transformer as a power source, four single phase inverters interconnected with DC-link capacitors and various electrical apparatuses, multiple controllers and control algorithms with high performance and reliability are needed. The major function of the compensating equipment is to manage reactive and active powers by using the four single phase inverters, so, the main control effort is focused on the power flow control which realized through the decoupling current control of the four inverters. Overall control system is designed with object oriented and analyzed on a Simulink window. The simulation results show that the design scheme is very effective for a complicated control system and the proposed controller has good performance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.427-428
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• 2008

We have studied design and application about an self generation equipment for underground power transmission cable. The split CT(Current Transformer), which has the applicable underground power transmission cable, was manufactured through electromagnetic simulation of magnetic core. And manufactured the AC-DC converter that supplied stable DC power for PLC modem when current of power line has more than 150A. An self generation equipment using the CT and AC-DC converter get into operation the PLC modem consistently. As a result, the underground power transmission cable was showed the application possibility through the stable communication and network characteristics.