• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.173-180
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• 2017

The main objective of a torque controller below rated wind speed is to extract maximum power from the potential wind energy. To do this, the torque control method, which adjusts the torque magnitude and makes it proportional to the square of the generator speed, has been applied. However, this method makes the response slower as the wind turbines are getting larger in size with multi-MW capacities. In this paper, a torque control method that uses the nonlinear parameter of rotor speed for aerodynamic torque as a control gain is discussed to improve the response by adjusting an additional torque magnitude. The nonlinear parameter of the rotor speed could be calculated both online and offline. It is shown that the offline case is more practical and effective in producing power through the numerical simulation of a 2MW wind turbine by considering the real turbulence wind speed.

• Fire Science and Engineering
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• v.31 no.6
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• pp.83-90
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• 2017

If an overcurrent exceeding the rated value is applied to an electric wire, the temperature of the electric wire increases, and the electric wire covering deteriorates to cause a short circuit. The upper limit temperature of the wire varies according to the magnitude of the overcurrent. When a short circuit occurs at each upper temperature limit, a cooling speed difference occurs during the solidification process due to the temperature difference between the short circuit temperature and the wire surface temperature. At this time, the pattern characteristics of the dendritic structure formed on the molten cross section are different. In this study, the upper temperature limit, which varied according to the overcurrent magnitude, was measured. At the time a short circuit occurred, the second branch spacing (dendrite Arm Spacing : DAS) of the dendrite was analyzed and the numerical value was quantified. The experimental results showed that the upper temperature limit increases with the magnitude of the overcurrent, and that the second branch spacing increases with increasing wire temperature.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.214-221
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• 2001

This paper describes the design of 3-component force/moment sensor with the force and moment ratio of wide range. It can measure the x-direction force Fx, y-direction force Fy and z-direction moment Mz simultaneously. In order to accurately measure forces and moment using 3-component force/moment sensor, it should get suitable force and moment ratio(the ratio of force Fx=200 N and moment Mz=20 Nm is ten to one), and small interference error. In this paper, in order to design the 3-component force/moment sensor with the force and moment ratio of wide range, the procedures are performed as follow : 1) the derivation of the equations to predict the bending strains on the surfaces of the plate-beams under the force or the moments, 2) the determination of the size of the sensing elements of the force/moment sensor by using the derived equations, 3) the Finite Element Method(FEM) analysis and the characteristic test for confirming the strains from the theory analysis, 4) the selection of the attachment locations of the strain gages of each sensor, 5) the analysis of the rated strain and the interference error at the attachment location of strain gages. It reveals that the rated strains calculated from the derived equations make a good agreement with the results from the Finite Element Method analysis and the characteristic test.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.04a
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• pp.161-161
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• 1996

본 연구에서는 차량(승용차) 시동용 수퍼캐패시터-밧데리 조합시스템에 적용할 시작품 전기이중층 수퍼캐패시터(super-capacitor:SC)를 설계 제작 개발하고 그 성능 특성을 확인하였다. 재래식의 차량용 밧데리의 비동력(specific power)이 100~200 W/kg에 비하여 전기이중층 SC의 경우는 1,000~3,000 W/kg으로 단위 총량당의 동력이 매우 크다. 또한 충방전시의 화학반응이 없는 관계로 인하여 충전식 2차 전지에 비하여 사용수명이 매우 길다. 이러한 SC를 기존의 밧데리와 함께 조합하여 차량 시동용으로 사용하게 되면 밧데리의 사용수명을 2~3배 길게 할 수 있으며 밧데리는 시동에 필요한 큰 전류의 방전이 요구되지 않으므로 그 용량과 크기가 대체로 절반이상 줄어든다. 또한 매우 낮은 온도의 기후조건에서는 밧데리의 방전효율이 급격히 저하되므로 이를 대비하여 필요 이상의 과용량, 과중량 밧데리의 사용이 실제로 행해지고 있으나 조합시스템의 차량 시동시에는 SC가 갖는 특성상 -5$0^{\circ}C$까지의 기후조건에서도 방전효율이 크게 저하되지 않은 채 시동전류를 공급해주므로 혹한지역이나 혹한시의 차량시동에도 탁월한 시동성능을 갖는다. 설계 제작된 SC는 저장에너지 6KJ, 정격전압 12Volt, 설계축전용량 70F 그리고 사용은 도 범위가 섭씨 영하 25도에서 영상 50도이며 무공해성 수용성 전해질을 사용하였으며, 제작된 CS는 사용온도 범위에서 축전용량 65F - 85F, 내부저항 1.8mOhm - 5.2mOhm의 변화를 보였으며, 정상시동에 필요한 방전전류 300Amp의 경우 2.6초의 방전시간, 약 89%의 방전효율을 보였다. 현재까지 상온하에서 30.000회의 충방전 시험결과로서는 방전효율의 저하가 없는 양호한 성능을 보였으며, SC의 시범 작동시험을 실차(소나타 1800cc)에 장착하여 수행한 결과 20회 이상의 연속시동에서도 아무런 문제점 없이 잘 동작하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2737-2743
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• 2015

The wind power plant must be able to produce reactive power at the POI bus of a wind farm connected to power system to keep or control the voltage of POI bus. But, the reactive power capability of wind turbines may not be sufficient to control the voltage of POI bus due to the reactive power losses in connection lines between wind farm and POI bus. The solution of this problem is to install an external STATCOM. The proposed cooperative control method of STATCOM and conventional reactive power compensators such as Switched-shunt and tap changing transformer can control the voltage of POI bus more efficiently. The simulation results are shown that the voltage drop of POI Bus of Test System with the arbitrary load change rate to initial loads is improved more than 60% and the voltage of load bus is maintained more than 95% of rated voltage.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.9-17
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• 2002

A high-efficiency electronic ballast for HID lamps is presented. The ballast consists of a PFC and a resonant inverter. To reduce losses of the ballast, DC link voltage should be determined by taking into account the peak voltage of lamp and the maximum flux density should be kept 0.2[T] on all of inductors. AR inductor at bridge diode is employed in order to remove currant harmonics from PFC. An inductor is connected in series with an electrolytic capacitor at DC link to reject high-frequency current. The acoustic resonance is eliminated using the stead spectrum technique. The electronic ballast for 250[W] metal-halide discharge lamp is implemented and 96[%] efficiency, no acoustic resonance and low conducted EMI level are accomplished.

• Journal of Energy Engineering
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• v.2 no.1
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• pp.28-37
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• 1993

This paper describes the development of a dynamic model of 1,000 MW$\_$e/ nuclear power plant including its local and integrated control system. The model was constructed using the Modular Modeling System (MMS) developed by the Electric Power Research Institute (EPRI) to provide an efficient, economical and user-friendly computer code for use in the analysis of the dynamic performance of nuclear and fossil power plants in conjunction with the Advanced Continuous Simulation Language (ACSL). Steady state for full load and transient results for turbine power step changes of loft are presented in this paper. The model includes most major components of a 1,000 MW$\_$e/ nuclear power plant and it can readily be modified to simulate a specific power plant. This procedure greatly reduces the analysis and modeling efforts involved in dynamic simulation of power plants and increases confidence in the analysis results.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.4
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• pp.79-84
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• 2011

This paper presents development activities of the T700/701K turbo-shaft engine for Korean Utility Helicopter(KUH). The T700/701K is the first rear-drive variant of the GE's T700 engine which is proven for military applications in the world. The main workscope of the development includes a modification from a front-drive engine to a rear-drive one, an performance enhancement of the power turbine and an incorporation of two channel FADEC(Full Authority Digital Engine Control) system for more reliable operation. The first engine run for development and qualification test was successfully completed in 2008. Since the PFRT(Preliminary Flight Rating Test) has been completed, the first flight of the engine installed in the first prototype of KUH has been successfully demonstrated in March, 2010 and the engine installation compatibility tests are being carried out during KUH flight test. The test and evaluation for qualification has been done except for the low cycle fatigue test up to date.

• Plant Journal
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• v.10 no.3
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• pp.45-51
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• 2014

This study performs several experiments on a newly developed temperature safety system that can be used for residential building heating systems, the heat source of which is derived from a conventional fuel cell. Prior to this, the hot water made from a fuel cell was not used in residential housing but just went to waste. The present safety system is installed in the current underfloor heating system. At first we used the CFD technique to develop a new heat exchanger. The fuel cell must satisfy the thermal conditions of the inlet temperature being $55^{\circ}C$ and the outlet temperature being $60^{\circ}C$. But variations in weather cause fluctuations in the heating water temperature. The experimental results show our new system capable of maintaining the temperature difference within a ${\pm}0.5^{\circ}C$ range. So we believe that our new PFMFC fuel cell stack array is a good candidate for being used in residential heating systems.

• Nuclear Engineering and Technology
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• v.27 no.3
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• pp.358-373
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• 1995

The Heat Transport system loop stability of CANDU-6 reactor using the CANFLEX fuel bundle was studied. The Thermal-hydraulic behavior of CANFLEX fuel bundle is similar to the conventional 37-element fuel bundle since the reactor power and the frictional pressure drop through the fuel channel is almost the same each other, Mounter the CANFLEX fuel bundle gives higher critical channel power and more homogeneous enthalpy distributions in the subchannels than 37-element fuel bundle. The SOPHT modelling or the CANFLEX fuel bundle and the Reactor outlet Header(ROH) interconnection line was made and the stability analysis response of Wolsong-1 reactor with CANFLEX fuel bundle was obtained. Without the ROH interconnection line the Heat Transport system loop using 43-element fuel bundle is unstable like the current 37-element fuel bundle. With the ROH interconnection line, however, the Heat Transport system is stable within $\pm$1％ of nominal flow. In the Heat Transport system loop stability point of view for Wolsong-1 plant therefore, the CANFLEX fuel loading is considered to be acceptable.