• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 춘계학술대회 논문집 전기설비전문위원
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• pp.35-36
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• 2007

We investigated the characteristics of three phase flux-lock type SFCL. Three phase flux-lock type consists of three reactor wound on an iron core in each single phase and the secondary coil is connected to the superconducting elements in series. the superconducting elements with serial connection were quenched simultangously in the single line-to-ground fault.

• Journal of Advanced Marine Engineering and Technology
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• 제38권1호
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• pp.8-14
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• 2014

본 연구에서는 R-245fa를 작동유체로 하는 250kW급의 선박폐열회수 발전 시스템을 설계하고 과열기의 구성에 따른 사이클 특성을 연구 하였다. 과열기와 증발기의 직렬연결과 병렬연결의 2가지 조건을 시뮬레이션 하였다. 과열기와 증발기의 직렬연결 시뮬레이션에서는 작동유체 과열에 따른 엔탈피 증가로 4.7%의 출력상승을 얻을 수 있었고, 목표출력을 250kW로 정하였을 경우에는 사이클유량을 4.1% 감소시킬 수 있었다. 과열기와 증발기의 병렬연결 시뮬레이션에서는 사이클의 목표출력을 250kW로 정하였을 경우에 과열기로 가는 열원유체의 유량이 증가함에 따라 사이클 유량이 감소하여 작동유체펌프의 소요동력이 최대 7.9% 감소 하였으며, 유량비율에 따른 사이클효율과 정미효율은 큰 변화가 없었다.

• 한국강구조학회 논문집
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• 제23권3호
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• pp.295-304
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• 2011

국내외적으로 강구조 약축접합부의 접합방법으로는 브라켓타입이 주로 사용되고 있다. 브라켓타입의 약축접합부는 기둥-보접합부를 공장에서 제작한 후, 현장에 운반하여 시공하므로 보이음부가 추가된다. 따라서 보이음부의 설치비용 및 공사기간이 증가되므로 강구조물의 경쟁력이 저하된다. 본 연구에서는 기존의 표준약축접합부를 개선하여 힘의 흐름이 명확하고, 접합상세가 간결하며, 시공성을 향상시킨 신형상 약축접합부를 제안하였다. 실험결과를 통하여 신형상 약축접합부는 기존의 표준약축접합부보다 최대내력이 크게 나타났으며, 또한 연성적으로 거동하는 것으로 나타났다. 여기서 기존의 표준약축접합부는 스칼럽 또는 보이음용접부에서 응력집중으로 인하여 파괴되는 반면에, 신형상 약축접합부는 응력이 집중되는 스칼럽 및 보이음용접부가 없으며, 또한 H형강기둥과 보를 결합하기 위한 용접플레이트의 두께를 자유롭게 조절할 수 있으므로 이러한 차이가 기둥-보접합부의 최대내력 증가 및 연성적 거동에 기여하는 것으로 판단된다.

• Steel and Composite Structures
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• 제6권3호
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• pp.203-219
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• 2006

One of the most promising ways through which a steel moment frame may attain high energy dissipating capability is to trim off a portion of the beam flanges near the column face. This type of moment connection, known as Reduced Beam Section (RBS) connection, has notable superiority in comparison with other moment connection types. As the result of the advantages of RBS moment connection, it has widely being used in practice. In spite of the good hysteretic behaviour, an RBS beam suffers from an undesirable drawback, which is local and lateral instability of the beam. The instability in the RBS beam reduces beam load-carrying capacity. This paper aims to investigate key issues influencing cyclic behaviour of RBS beams. To this end, a numerical analysis was conducted on a series of steel subassemblies with various geometric properties. The obtained results together with the existing experimental data are used to study the instability of RBS beams. A new slenderness concept is presented to control an RBS beam for combined local and lateral instability. This concept is in good agreement with the numerical and experimental results. Finally, a model is developed for the prediction of the magnitude of moment degradation owing to the instability of an RBS beam.

• Journal of Power Electronics
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• 제16권4호
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• pp.1298-1305
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• 2016

This paper presents the development of a short-circuit protection mechanism on a high voltage switch (HVS) board which is built by a series connection of semiconductor switches. The HVS board is able to quickly detect and limit the peak fault current before the signal board triggers off a gate signal. Voltage clamping techniques are used to safely turn off the short-circuit current and to prevent overvoltage of the series-connected switches. The selection method of the main devices and the development of the HVS board are described in detail. Experimental results have demonstrated that the HVS board is capable of withstanding a short-circuit current at a rated voltage of 10kV without a di/dt slowing down inductor. The corresponding short-circuit current is restricted to 125 A within 100 ns and can safely turn off within 120 ns.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.87-89
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• 2005

This paper proposes new series and parallel Sin+Cos PSS(power system stabilizer) for the purpose to improve the existing PSS1A's performance. The purpose of PSS is used to enhance damping of power system oscillations through injection of auxiliary signal for an excitation control terminal. The Proposed series and Parallel Sin+Cos PSS is connected adding the Sin+Cos terms additionally with serial and with parallel connection in a conventional PSS1A. The proposed controller is aim to considering of a damping of oscillation when it changes parameter fluctuations or operational load variations in a power system. The object of electric power system is KEPCO system and the voltage of power transmission line is a 154kV and a 345kV. The PSCAD/EMTDC package is used to authorize the effect of the proposed controller. Simulations were shown by and compared with the waveforms for frequency, voltage and electric power.

• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.35-45
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• 1996

The purpose of this paper is to investigate experimentally the strength and deformation of T-joints to improve the structural behavior of truss connection consisted in square hollow steel section. There are two-types to be changed in T-joint shape. One type is TP-series that a brace member is rotated to 45 degree, another type is TR-series that a chord member is rotated to 45 degree. The most important results obtained from the 2nd experiment on the T-joints is as follow; The yielding strength and initial stiffness of TP-series increase more than a current type(TS-series) in $0.6{\leq}{\beta}(d/D){\leq}0.7(0.85{\leq}{\beta}$'$(={\sqrt2}{\cdot}{\beta}){\leq}1.0)$.

• Journal of Power Electronics
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• 제10권4호
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• pp.388-395
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• 2010

An active boost converter for a single phase SRM using series-parallel connected capacitors is proposed in this paper. The proposed active boost converter has two diodes and one power switch with an anti-parallel diode and one additional boost capacitor. The additional boost capacitor could be series or parallel connected to the dc-link capacitor to produce proper excitation and demagnetization voltage. The proposed active boost converter can easily achieve a fast excitation and demagnetization from the capacitor connection. In this paper, series and parallel connected converters are reviewed, and the detailed operating modes as well as the voltage characteristics of the proposed converter are analyzed. The simulation and experimental results shows the effectiveness of the proposed active boost converter.

• Wind and Structures
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• 제31권1호
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• pp.1-14
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• 2020

This paper presents a method of estimation of fatigue demands on connection bolts of tubular steel wind turbine towers. The presented method relies on numerical simulation of aerodynamic loads and structural behavior of bolted connections modeled using finite element method. Variability of wind parameters is represented by a set of values derived from their probability densities, which are adjusted based on field measurements. Numerically generated stress time-series show agreement with the measurements from strain gauges inside bolts, in terms of power spectra and the resulting damage. Position of each bolt has a determining effect on its fatigue damage. The proposed framework for fatigue life estimation represents the complexities in loading and local behavior of the structure. On the other hand, the developed procedure is computationally efficient since it requires a limited number of simulations for statistically representing the wind variations.

• Structural Engineering and Mechanics
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• 제6권5호
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• pp.571-582
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• 1998

Testing of steel roof purlins is usually performed on full scale models in large vacuum test rigs. To undertake a comparison between web cleat connected purlins and flange bolted purlins a series of tests were performed on a 1:4 small scale model vacuum test rig. Various modelling issues need to be addressed to ensure reasonable comparison with actual constructed roof framing methods but still be suitable for an economical comparison between the connection methods. Model test results were supported by, and found to be in reasonable agreement with, deflection predictions from computer models based on finite element methods. This paper discusses the testing methods adopted and the value of small scale model testing programs as a means of obtaining comparisons between framing options.