• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.521-524
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• 1996

A new zero voltage and nero current switching(ZVZCS) full bridge(FB) PWM converter b proposed to improve the performance of the previously presented ZVZCS-FB-PWM converters [7,8]. By adding a secondary active clamp and controlling the clamp switch moderately, ZVS(for leading-leg switches) are ZCS(for lagging-leg switches) are achieved without nay lossy components, the reverie avalanche break down of leading-leg IGBTs[7] or the saturable reactor in the primary[8]. Many advantages including simple circuit topology, high efficiency, and low cost mate the new converter attractive for high voltage and high power(> 10 kW) applications. The principle of operation is explained and analyzed. The features and design considerations of the new converter are also illustrated and verified on an 1.8 kW, 100 kHz IGBT based experimental circuit.

• 대한기계학회논문집B
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• 제33권5호
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• pp.299-310
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• 2009

Fuel cells are expected to be promising future power sources in both aspects of thermal efficiency and environmental friendliness. Accordingly, worldwide research and development efforts have been enormously increasing recently in various applications such as power plants, transportation and portable power sources. Among others, high temperature fuel cells, such as solid oxide fuel cells and molten carbonate fuel cells, are suitable for electric power plants. Moreover, their high operating temperature is quite appropriate to construct further advanced integrated systems. This paper reviews recent literatures on research and development of integrated power generation systems based on high temperature fuel cells. Research and development efforts are summarized in the area of fuel cell/ gas turbine hybrid systems, application of carbon capture technology to fuel cell systems, integration of coal gasification with fuel cells, and the use of alternative fuels.

• Nuclear Engineering and Technology
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• 제49권1호
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• pp.224-233
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• 2017

In Korea, attempts have been made to develop high strength concrete for the safety and design life improvement of nuclear power plants. In this study, the cracking potentials of nuclear power plant-high strength concretes (NPP-HSCs) containing industrial by-products with W/B 0.34 and W/B 0.28, which are being reviewed for their application in the construction of containment structures, were evaluated through autogenous shrinkage, unrestrained drying shrinkage, and restrained drying shrinkage experiments. The cracking potentials of the NPP-HSCs with W/B 0.34 and W/B 0.28 were in the order of 0.34FA25 > 0.34FA25BFS25 > 0.34BFS50 > 0.34BFS65SF5 and 0.28FA25SF5 >> 0.28BFS65SF5 > 0.28BFS45SF5 > 0.28 FA20BFS25SF5, respectively. The cracking potentials of the seven mix proportions excluding 0.28FA25SF5 were lower than that of the existing nuclear power plant concrete; thus, the durability of a nuclear power plant against shrinkage cracking could be improved by applying the seven mix proportions with low cracking potentials.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1559-1561
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• 2003

In northeast Asia, there will be several important HVDC transmission lines to be established in Korea and China for perspective electric network market. 5500V 4-inches High voltage thyristor can be used in the DC transmission and distribution of electric power system. In this application, many thyristors are connected in series for each thyristor valves. Therefore, the required low reverse-recovery charge QRR and low on-state voltage drop $V_{TM}$ for such thyristor is necessary to this application. In our work, the on-state and off-state voltage performance was simulated by commercial simulation software.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.339-343
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• 2006

We observed the application possibility of inductive coupler for the underground high-voltage power line communication by means of analysis of signal transmission characteristics and magnetic properties on annealing temperatures for high-permeability Fe-base amorphous alloys. The best electromagnetic and transmission characteristics were shown in nano-crystalline precipitated alloy annealed at temperature $510^{\circ}C$. The transmission characteristics in the low-frequency band depend on permeability of magnetic core materials and its properties of high-frequency band can be improved by impedance matching. Using the high pass filter embedded in the coupler, other noise signal band except for communication signals could be cut off.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1369-1374
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• 2014

Most accidents of medium-voltage cables installed in nuclear power plants result from the initial defect of internal insulators or the initial failure due to poor construction. However, as the service years of plants increase, the possibility of cable accidents is also rapidly increases. This is primarily caused by electric, mechanical, thermal, and radiation stresses. Recently, much attention is paid to the study of cable diagnoses. To date, partial discharge and Tan${\delta}$ measurements are known as reliable methods to diagnose the aging of medium-voltage cables. High frequency partial discharge measurement techniques have been widely used to diagnose cables in transmission and distribution systems. However, the on-line high frequency partial discharge technique has not been used in the nuclear power plants because of the plant shutdown risk, degraded measurement sensitivity, and application problems. In this paper, the partial discharge measurement with a portable device was tried to evaluate the integrity of the 4.16kV and 13.8kV cable lines. The test results show that the high detection sensitivity can be achieved by the high frequency partial discharge technique. The present technique is highly attractive to diagnose medium voltage cables in nuclear power plants.

• 전력전자학회논문지
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• 제25권3호
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• pp.188-194
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• 2020

This paper presents a high-efficiency Switch Mode Line Transformer (SMLT) composed of load-shared dual modules, which is based on the AC/AC LLC resonant converter. Given that the conventional adaptor is usually composed of two power stages, namely, the PFC and DC/DC converters, its system size can be increased according to the output power. However, given that the proposed SMLT can separate the PFC converter from the adaptor, the size reduction of the system can be achieved. Meanwhile, the SMLT with a single module has the limit of the size reduction because of a high resonant current. Thus, it can be configured with dual or multiple modules to reduce the resonant current. Then, their load sharing can be guaranteed by only the proposed transformer structure without an extra current controller. The validity of the proposed converter is proven through a 850-W prototype.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.144-145
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• 2005

In this study, we have developed the high resolution multichannel seismic data acquisition system and shallow marine seismic source. It is easy to operate our source system which utilizes piezoelectric transducer of high electrical power. According to water depth, survey condition and purpose, transducer number of source system can be easily changed in order to maximize field applicability. In the recording part, we used 24 bits and 8 channel high speed A/D board in order to achieve the improvement of data quality and the efficiency of data acquisition. The developed system was tested and varied with the data acquisition parameters such as source-receiver offset, and transducer number versus water depth for the field application.

• Journal of Power Electronics
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• 제15권5호
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• pp.1380-1391
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• 2015

This paper provides a loss analysis and comparison of high power semiconductor devices in 5MW Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) Wind Turbine Systems (WTSs). High power semiconductor devices of the press-pack type IGCT, module type IGBT, press-pack type IGBT, and press-pack type IEGT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on the back-to-back type 3-level Neutral Point Clamped Voltage Source Converters (3L-NPC VSCs) supplied from a grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through a loss analysis considering both the conduction and switching losses under the operating conditions of 5MW PMSG wind turbines, particularly for application in offshore wind farms. This paper investigates the loss analysis and thermal performance of 5MW 3L-NPC wind power inverters under the operating conditions of various power factors. The loss analysis and thermal analysis are confirmed through PLECS Blockset simulations with Matlab Simulink. The comparison results show that the press-pack type IGCT has the highest efficiency including the snubber loss factor.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.43-45
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• 2002

High current density Bi-2223 tapes have recently become commercially available. There are some important characteristics of the tapes, e.g. critical current, ac loss, fault current characteristics, for an application such as a power cable or a power transformer. They have been investigated experimentally and discussed in this paper.