• 조명전기설비학회논문지
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• 제26권2호
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• pp.51-60
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• 2012

An improved method for detecting fault distance in overhead transmission lines is described in this paper. Based on single-ended measurement, propagation theory of traveling waves together with the wavelet transform technique is used. In estimating fault location, a simple, but fundamental method using the time difference between the two consecutive peaks of transient signals is considered; however, a new method to enhance measurement sensitivity and its accuracy is sought. The algorithm is developed based on the lattice diagram for traveling waves. Representing both the ground mode and alpha mode of traveling waves, in a lattice diagram, several relationships to enhance recognition rate or estimation accuracy for fault location can be found. For various cases with fault types, fault locations, and fault inception angles, fault resistances are examined using the proposed algorithm on a typical transmission line configuration. As a result, it is shown that the proposed system can be used effectively to detect fault distance.

• 전기전자학회논문지
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• 제26권3호
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• pp.456-461
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• 2022

본 논문에서는 차동 증폭기에 필수적으로 필요한 Radio frequency(RF) transformer(TF)을 활용하여 광대역 이득 특성을 가지는 2단 단일 종단 전력증폭기를 제시하였다. RF TF의 특징을 파악하고 광대역 특성을 가지도록 설계한 뒤 2단 전력증폭기의 단간(inter-stage) 임피던스 정합 회로에 적용함으로써 증폭기의 대역폭을 향상시킬 수 있다. 기존의 2단 단일 종단(Single-ended) 증폭기의 성능과 면적을 유지하면서 광대역 이득 특성을 얻을 수 있도록 단간 정합 회로를 Monolithic Microwave Integrated Circuit (MMIC)와 다층 PCB에 구현하고 시뮬레이션을 통해 결과를 비교하였다. InGaP/GaAs HBT 모델을 사용하여 설계한 2단 전력증폭기 모듈을 시뮬레이션 한 결과 중심주파수 3.3GHz에서 기존의 전력증폭기가 11.2%의 fractional 대역폭을 보인 반면 제안된 설계 기법을 적용한 전력증폭기는 19.8%의 개선된 대역폭을 가짐을 확인하였다.

• 전기학회논문지
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• 제58권1호
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• pp.77-85
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• 2009

With the advent of power semiconductor switching devices, power electronics relating to high frequency electromagnetic eddy current based induction heating technology have become more suitable and acceptable. This paper presents high-frequency induction heating cooking appliance circuit based on the zero current switching-PWM single ended push-pull(ZCS-PWM SEPP) resonant inverter added AC-DC converter. This inverter uses pulse-width-modulation(PWM) control method with active auxiliary quasi-resonant lossless inductor snubbers and a switched capacitor. To improved the transient performance, the PI controller is applied for this system. For the systematic parameter optimization of the PI controller, the gradient-based optimization algorithm is applied. The performance of optimized parameters is evaluated using simulation and experimental test. These results show that the proposed systematic optimal tuning method improve the transient performances of this system.

• 대한기계학회논문집B
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• 제29권1호
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• pp.27-34
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• 2005

We analyze in detail axially symmetric theoretical study for the photothermal pulsed radiometry of a cylindrical model. The theoretical solutions describe the transient infrared radiation from the sample heated by short-duration pulsed heating. In the conventional transmission radiometry technique, the excitation source and the detector are on opposite sides of the sample, otherwise in the new single ended radiometry technique, the excitation source and the detector are on same sides of the sample. The analytical solution described for photothermal radiometry in this study would not need to cut or polish samples to measure the thermal diffusivity. Therefore the radial area and axial thickness of samples are not limited. The effects of excitation pulse duration and the area of heat source are discussed.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.790-802
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• 2017

This paper proposes the modeling and control strategy to track the MPPs of hybrid PV and Wind power systems, using a new dual input boost converter. The dual input power conditioning system with an independent MPPT control scheme is introduced with minimum number of circuit elements in order to reduce the switching loss, size and cost of the system. Since the operating conditions for the PV and Wind power systems are very distinct from each other, an efficient and superior control system is required to track the MPPs of both renewable sources with the use of a simply-structured single-ended single-inductor converter. The design of Power-Conditioning System (PCS) and detail control strategy are presented in this paper. To provide independent tracking of MPPs, a variable duty-cycle control strategy is employed for the wind system and a variable frequency strategy is employed for the PV system. Finally, the proposed dual-input converter for hybrid power conditioning system is implemented and the hardware test results are presented. From the hardware experiment, it is concluded that the proposed system successfully tracks the MPPs of both of the renewable power systems independently.

• Current Optics and Photonics
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• 제3권5호
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• pp.458-465
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• 2019

The thermal effect and the light output of a laser crystal under different pumping depths were reported., Based on the thermal model of a single-ended pumped Tm:YAP crystal, the thermal stress coupled model used Comsol to theoretically calculate the effect of changing the pump spot size and pump depth on crystal heat distribution and stress distribution. The experimental results showed that the laser output power first increased and then decreased with increasing pump spot size. As the depth of focus increased, the laser output power first increased and then decreased. The experimental results were consistent with the theoretical simulation results. The theory of pump spot radius and depth of focus in this paper provided an effective simulation method for mitigating thermal effects, and provided theoretical supports for laser crystals to obtain higher laser output power.

• 조명전기설비학회논문지
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• 제17권4호
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• pp.20-25
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• 2003

본 논문은 기존 전자식 안정기에 사용되던 Boost 컨버터 형태의 역률 개선 부분을 SEPIC 컨버터 형태를 갖는 역률 개선 방식으로 대치하여 특성을 확인한 논문이다. Boost 컨버터 형태를 갖는 역률 개선 방식의 출력 DC 전압은 일반적으로 400[V]이며, 최소 전압은 입력 전원의 실효값 이상이어야만 한다. 하지만 SEPIC 컨버터 구조를 이용하면, 역율 개선 효과뿐만 아니라, 입력 전원의 실효값 보다 작은 출력 DC 전압을 얻을 수 있다는 장점을 가지고 있다. 본 논문에서는 SEPIC 컨버터 구조를 갖는 역율 개선 방식과 링코어를 이용한 자려식 발진 방식을 적용한 전자식 안정기를 제작하였고, 낮은 출력 전압을 이용하여 소자의 용량과 크기를 감소시켰다.

• 전력전자학회논문지
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• 제9권3호
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• pp.285-293
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• 2004

본 논문에서는 능동역률보상(PFC)의 구조를 가진 SEPIC 컨버터를 이용한 무전극 형광램프(electrodeless fluorescent lamps)용 전자식 안정기를 제안하였다. SEPIC 컨버터는 입력 전류의 낮은 고조파와 고역률의 특성을 가진다. 제안된 제어방법으로는 UC3854의 적분회로를 이용한 것으로 이 기술은 전류연속모드로 동작하는 역률보상 및 과전류보호를 제공하는 매우 간단한 제어 회로이다. 제안된 무전극 형광램프용 전자식 안정기는 3개의 무전극 형광램프용으로 설계되어 기존의 무전극 형광램프용 전자식 안정기보다 에너지 및 제작비 절약 효과가 크다. 제안된 안정기의 특성을 측정하기 위해 실험을 실시하였으며 이를 통해 고역률과 낮은 THD를 확인하였다.

• 한국도로학회논문집
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• 제18권5호
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• pp.75-82
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• 2016

PURPOSES : This study was initiated to estimate the benefits from the campaign to prevent drowsy driving crashes on expressways. The study was conducted by the Korea Expressway Corporation using a contingent valuation method. METHODS : First, a questionnaire was designed for a preliminary survey. From the survey's results, the initial willingness to pay for the campaign was determined by averaging different amounts of payments chosen under virtual scenarios in the survey. The willingness to pay data was used to find a first bid price for the open-ended method used for the second survey. After that, a primary questionnaire was designed and conducted using a single dichotomous choice question (SDBCQ). Drivers at expressway resting areas were asked their willingness to pay for the campaign. Based on statistical analysis using data collected from the second survey, the mean willingness to pay was estimated using a probability utility function. Finally, the benefit from the campaign was calculated using the estimated willingness to pay and accident data on expressways. CONCLUSIONS : Based on the result from the contingent valuation method, the benefit from the campaign to prevent drowsy driving crashes was estimated to be 170.6 won per expressway trip. The benefit is to be paid as an additional toll. In addition, the traffic crash cost estimate is about 2,209,680,000 won less than the cost during the same period in 2014.

• Geomechanics and Engineering
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• 제15권1호
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• pp.695-710
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• 2018

Formation of a soil plug in an open-ended pile is a very important factor in determining the pile behavior both during driving and during static loading. The degree of soil plugging can be represented by the incremental filling ratio (IFR) which is defined as the change in the plug length to the change of the pile embedment length. The experimental tests carried out in this research contain 138 tests that are divided as follows: 36 tests for single pile, 36 tests for pile group ($2{\times}1$), 36 tests for pile group ($2{\times}2$) and 30 pile group ($2{\times}3$). All tubular piles were tested using the poorly graded sand from the city of Karbala in Iraq. The sand was prepared at three different densities using a raining technique. Different parameters are considered such as method of installation, relative density, removal of soil plug with respect to length of plug and pile length to diameter ratio. The soil plug is removed using a new device which is manufactured to remove the soil column inside open pipe piles group installed using driving and pressing device. The principle of soil plug removal depends on suction of sand inside the pile. It was concluded that the incremental filling ratio (IFR) is changed with the changing of soil state and method of installation. For driven pipe pile group, the average IFR for piles in loose is 18% and 19.5% for L/D=12 and 15, respectively, while the average of IFR for driven piles in dense sand is 30% and 20% for L/D=12 and L/D=15 respectively. For pressed method of pile installation, the average IFR for group is zero for loose and medium sand and about 5% for dense sand. The group capacity increases with the increase of IFR. For driven pile with length of 450 mm, the average IFR % is about 30.3% in dense sand, 14% in medium and 18.3% for loose sand while when the length of pile is 300 mm, the percentage equals to 20%, 17% and 19.5%, respectively.