• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.81-86
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• 2013

Exhaust gas from a small portable electric generator is simply exhausted to the surroundings because the capacity and quality of the waste heat of this gas is generally not sufficient to recover and utilize. We have proposed a seawater distiller utilizing the thermal energy of waste gas from an electric generator. The distiller recovers heat from the waste gas by means of a heat pipe and uses it effectively through a multiple-effect diffusion-type structure. We constructed an experimental apparatus with a vertical single-effect still having a 4-stroke 50 cc generator engine and found that the experimental results for distillate productivity show good agreement with the theoretical predictions. The results show that the distiller can recover 52 W of waste heat from the gas at $171^{\circ}C$, and ~85% of the recovered heat can be utilized for distillation to produce 70 g/h of fresh water. This is equivalent to a productivity of 500 g/h in the case of a 10-effect still. Therefore, the proposed distiller should be useful in remote areas where electricity and water grids are inadequate.

• Journal of the Korean Solar Energy Society
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• v.32 no.2
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• pp.95-104
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• 2012

This study purposed to predict wind energy for small size wind power generators at 50m above the ground in each area using mean wind speed data for 10 minutes collected from 2001 to 2011 by meteorological data in large cities having over 60% of 15 story (50m) or higher apartments including Seoul, Daejeon, Gwangju and Daegu representing the inland region, and Busan, Incheon and Ulsan representing the coastal region. In the results of analysis, we confirmed close agree ment between observatory weather data and probability density distribution obtained using Weibull's parameters, and this suggests that Weibull's parameter is applicable to the estimation of wind energy. Hourly output energy using the mean wind speed for 10 minutes and output energy obtained from Weibull's parameter showed an error less than 5%, and thus it was found that wind energy can be evaluated using Weibull's modulus.

• Journal of the Korean Solar Energy Society
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• v.30 no.4
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• pp.1-8
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• 2010

The mechanical parts of small windp ower generator less than 10kW are manufactured in the form of removing most of the accelerators. The braking system to protect blade from damages caused by high wind speed is manufactured in a manner having apparatus system(furling), manual brake or no brake. This study is on braking system in small size wind power generator, and carried out survey as following steps by applying electric braking system which uses armature reaction. We explained the principle of electric braking system and the principle of existing braking system. Also, this paper interpreted short circuit current through open circuit and short circuit, as well as checking brake system's action using armature reaction with real construction of control device.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.508-509
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• 2008

마이크로그리드는 소형 분산 에너지원(MicroSource)으로 이루어진 분산전원망의 총칭으로 다수의 수용가들을 위하여 수요지에서 전력을 생산 및 공급하는 기술로 기본적으로 여러 수용가의 부하 및 분산발전기들이 하나의 덩어리를 형성하게 되는 새로운 개념의 배전망이다. 계통과 분리하여 운전이 가능한 마이크로그리드는 계통 연계 시 과도현상을 줄이기 위해 연계지점의 전압, 주파수, 위상을 일치하여 투입되어야 한다. 본 논문에서는 마이크로그리드 계통 재 연계 시 과도 특성을 모의한 결과를 제시하였다. 전력계통과의 분리 후 MicroSource의 전압의 크기, 주파수 및 위상을 제어하여 전력계통에 재연계하여 과도현상을 모의하는 기초연구를 진행하였다.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.835-836
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• 2006

최근의 선박 추진시스템은 기존의 엔진, 터빈 등의 구동 원에서 선박의 발전기로부터 선체 외부의 프로펠러와 일체형으로 구성된 모터를 구동하여 추진하는 전기추진식으로 변화되고 있다. 특히, 히토류계 영구자석재질의 발달로 인하여 대형 선박의 추진을 위한 대용량 자석계자형 BLDC와 영구자석형 동기전동기의 설계가 가능해 졌으며, 이에 대한 연구구도 활발히 이루어지고 있다. 그러나 이도 중 소형 선박기기에 한정되어 있으며, MW급 이상의 대형기기의 설계 연구도 일부 선진국에서만 진행 되고 있는 실정이다. 이에 본 연구에서는 5MW, 150rpm급 대용량 추진전동기 설계에 관한 연구를 하였다. 본 설계 모델은 오랜 기간 해양 운행을 해야 하는 선박특성 상 중요한 부분인 에너지 효율을 높이기 위하여 인버터를 전동기 내부에 배치한 구조로 부피와 중량을 줄이고, 더불어 속도에 따라 인버터를 커플링하여 상변환이 가능한 전동기를 설계하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1820-1827
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• 2012

This paper is to present a new method of cogging torque reduction for axial flux PM machines of multiple rotor surface mounted magnets. In order to start softly and to run a power generator even the case of weak wind power, reduction of cogging torque is one of the most important issues for a small wind turbine, Cogging torque is an inherent characteristic of PM machines and is caused by the geometry shape of the machine. Several methods have been already applied for reducing the cogging torque of conventional radial flux PM machines. Even though some of these techniques can be also applied to axial flux machines, manufacturing cost is especially higher due to the unique construction of the axial flux machine stator. Consequently, a simpler and low cost method is proposed to apply on axial flux PM machines. This new method is actually applied to a generator of 1.0kW, 16-poles axial flux surface magnet disc type machine with double-rotor-single-stator for small wind turbine. Design optimization of the adjacent magnet pole-arc which results in minimum cogging torque as well as assessment of the effect on the maximum available torque using 3D Finite Element Analysis (FEA) is investigated in this design. Although the design improvement is intended for small wind turbines, it is also applicable to larger wind turbines.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.1
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• pp.43-48
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• 2001

In conventional wind generation systems, since the blade rotates at low speed when the velocity of wind decreases their operations are possible only under limited conditions. Therefore they are in trouble of self-generation without the help of auxiliary generation devices outside. In addition, most of them have very low usage efficiency because of the characteristic changes of wind. For the solution of these problems and for enough generation regardless of districts and geographical features the rotation energy stored in a spring drives a compact generator and then electric power is stored at battery and supplied to the load continuously according to the lack of wind force. In this paper, the fabricated system consisting of a wind generator and power storage apparatus was introduced and its operation characteristics were analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.935-942
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• 2000

In this paper, miniature voltage-controlled oscillator(VCO) for 1.6GHz PCS band is designed and implemented. Colpitts type LC resonating oscillator is designed with multilayer PCB and circuit parameters are optimized using the circuit simulator. Using the optimized design parameters, miniature VCO with 6X6X1.8mm3 (0.065cc)dimensions is fabricated and experimented. Developed VCO has -1.67dBm $\pm$0.5dBm output power level in52.5MHz tunung range, and has -99.33dBc/Hz phase noise performance at 10 KHz frequency offset.

• The KSFM Journal of Fluid Machinery
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• v.16 no.4
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• pp.22-27
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• 2013

The purpose of this paper is to perform the structural design of the small scale vertical-axis wind turbine (VAWT) blade using a response surface method(RSM). First, the four design factors that have a strong influence on the structural response of blade were selected. Analysis conditions were calculated by using the central composite design(CCD), which is a typical design of experiment for the response surface method(RSM). Also, the significance of the central composite design(CCD) was verified using analysis of variance(ANOVA). The finite element analysis was performed for the selected analytical conditions for the application of response surface method(RSM). Finally, a optimization problem was solved with a objective function of blade weight and a constraint of allowable stress to achieve a optimal structural design of blade.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.1
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• pp.70-77
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• 2005

A new converter to transfer energy from a low-voltage AC current source to a battery is proposed. It is focused to find operational modes of the converter. The low-voltage AC current source is an equivalent of the piezoelectric generator, which converts the mechanical energy to the electric energy. The converter consists of a full-bridge MOSFET rectifier and a MOSFET boost converter in order to make the converter small and efficient. The operational principle and modes of the converter are investigated with the consideration of effects of the parasitic capacitances of MOSFETs and diode. The results are proved with simulation studies using PSIM and Pspice.