• Journal of Korea Water Resources Association
• /
• v.57 no.10
• /
• pp.687-697
• /
• 2024

Providing a uniform velocity distribution at the inlet of the experimental flume through removing eddies, air bubbles, swirling flow and excessive velocity fluctuations as quickly and efficiently as possible is very important for the accurate reproduction and measurement of both flow velocity and phenomenon in the test reach. In this study, the flow straightener (FS) using multiple parallel PC (ploycarbonate) tubes was developed to increase the accuracy of flow measurement by quickly eliminating excessive velocity fluctuations and air bubbles. It was confirmed through a series of hydraulic experiments that FS using PC tubes can reduce the turbulence intensity (TI) by nearly half under all experimental configurations. The FS of PC tubes with a diameter of 20 mm and a length of 0.3 m can reduce the TI by more than 60% and the value can be maintained at about 2.4% that is in common at the inlet cross-section of the experimental flume. When the tube length is 0.3 m, the magnitude of TI decreases linearly as the tube diameter decreases, and it is desirable to keep the tube diameter at 20 mm to provide a definite flow conditioning effect. Small air bubbles formed at high flow conditions are found to grow in size and quickly rise to the free surface at the rising velocity of about 0.24 m/s due to increased buoyancy as they pass through the tubes. The removal function of air bubbles was not sensitive to the diameter and length of the PC tubes.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.7
• /
• pp.726-731
• /
• 2005

Sedimentation is treated as the most important unit process in waterworks, and plays great role on turbidity removal efficiency. Rectangle sedimentation basin is the most widely accepted sedimentation process. But it has some problems with short-circuit flow and density flow caused by temperature and influent turbidity variation. To solve these problems, installation of rectification wall was suggested, but not generally fully accepted in field. Because hole of rectification wall cause jet flow. In this research, use of moving baffle was investigated. Moving baffle was designed to induce uniform velocity at every section of water flow. The baffle walls was made from soft fiber materials. The baffle walls with flow of sedimentation basin moves at same speed. It is like that it controls density flow and short-circuit flow and induce uniform velocity at every section of water flow in sedimentation basin. When moving baffle was operated retention time of sedimentation basin was extended to 1 hours. When it talked again and the effluent time of highest concentration of the chlorine ion from 100 minutes was extended to 160 minutes. Turbidity removal efficiency was tested with different operation modes(continuous and batch) with influent turbidity and retention time. It was revealed that turbidity removal efficiency carl be improved up to 36%(continuous mode) and 58%(batch mode) respectively. Consequently if moving baffle introduces in Rectangle sedimentation basin, it forecasts that the turbidity improvement above 30% will be possible.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.1
• /
• pp.413-419
• /
• 2011

Diagnosis X-ray equipment localized at 1950's but it is developed suddenly at 1960's with demand together. Manufacture of Diagnostic X-ray equipment is controled by the KS regulation and the Ministry of Health and Welfare because of hazardous element etc. exposure by radiation. Most of diagnostic X-ray equipment ware single phase and three phase full-wave rectification but from 1980's it transforms it was exchanged in inverter type X-ray equipment. Inverter type X-ray equipment produces approximately 50~80% more average photon intensity then single phase full-wave rectification and the accuracy is high. But from a clinic it dose not use because expensive therefor the efficiency improvement of single phase full-wave rectification is necessary. We produced single phase full-wave rectification X-ray equipment control unit, high tension transformer, filament heating transformer, rectification circuit, high tension cable and others and evaluated efficiency, in result which is excellent compare with Rule of Safety Management and KS regulation.

• Proceedings of the KIEE Conference
• /
• 1999.07g
• /
• pp.3172-3174
• /
• 1999

교환기나 전송장치 등 각종 통신설비에 전원을 공급하기 위해서 정류기, 축전지 및 발전기 등의 전원설비가 사용되고 있다. 이들 중에서도 정류기는 통신설비에 직류전원을 공급하기 때문에 다른 전원설비 보 다도 신뢰성 및 안정성이 확보된 장치로 인식되어 왔다. 그러나 현재 사내전화국에 설치 운용중인 정류기는 교환 기별로 종류가 다양하여 유지보수에 어려움이 내재하고 있을 뿐만 아니라 통신망의 광대역화, 대용량화에 대처가 곤란하며 정류기를 전력실 또는 통신실에 집중해서 설치 운용하는 집중공급방식으로는 축전지의 만충전이 곤란하다. 또한 현재의 이러한 급전방식은 통신장치의 광대역화, 고도화 등 통신망의 급격한 발전과 함께 다음과 같은 문제점이 대두되고 있다. 첫째, 전력실에서 총괄하여 교류전력을 직류48V로 변환해서 급전하기 때문에 급전전류가 크게되고, 또한 전력실에서 통신실까지의 급전손실이 크다 둘째, 통신설비의 증감에 따른 전원설비의 증감이 어렵기 때문에 설비 가동율이 나쁘다 셋째, 전원설비의 고장에 의한 전화국 전체설비에 심각한 영향을 미칠수 있다 이러한 문제점을 해소하기 위하여 집중 및 분산급전방식으로 운용이 가능하며, 또한 모든 전원설비를 감시/제어하는 전원 집중관리 시스템과의 인터페이스 등이 가능한 정류시스템을 1997년부터 개발하였다. 본고에서는 신형 정류기와 기존의 정류기와의 성능 및 특성에 대해 비교하였고, 특히 경제성측면과 설치상련에 대해 비교분석 하였다. 또한 집중급전방식과 분산급전방식의 특성에 대해서도 서술하였다.

• 전기의세계
• /
• v.25 no.4
• /
• pp.24-27
• /
• 1976

차례 1.직류송전의 개요 2.직류송전의 변환장치 3.정류기 1)수은정류기 2)싸이리스터 3)수은정류기와 싸이리스터의 비교

• Journal of radiological science and technology
• /
• v.37 no.3
• /
• pp.187-193
• /
• 2014

The purpose of this study was to analyze the effect on the selectivity on of high-voltage rectification device that measured the performance of the grid, and the contrast improvement ability (K factor) by measuring the scattered radiation content of the transmitted X-rays. The scattered radiation generated when the X-ray flux comes from the diagnostic X-ray generator that passes through an object. Targeting four different rectifications of X-ray generators, the mean value of the tube voltage and the tube current was measured in order to maximize the accuracy of the generating power dose within the same exposure condition. Using fluorescence meter, the content of the scattered rays that are transmitted through the acrylic was measured depending on the grid usage. When grid is not used, the content of the scattered rays was the lowest (34.158%) with the single-phase rectifier, was increased with the inverter rectifier (37.043%) and the three-phase 24-peak rectification method (37.447%). The difference of the scattered radiation content of each device was significant from the lowest 0.404% to the highest 3.289% while using 8:1 grid, the content of the scattered ray was the lowest with the single content of the scattered ray was the lowest with the single-phase rectifier (18.258%), was increased with the rectifier (25.502%) and the 24-peaks rectification (24.217%). Furthermore, there was difference up to content 7.244% to the lowest content 1.285% within three-phase 24-peaks rectification, inverter rectifications, and single-phase rectifier depending on the selectivity of the grid. Drawn from the statistical analysis, there was a similar relationship between the contrast improvement factor and the K factor. As a result, the grid selectivity and the contrast were increased within the single-phase rectifier rather than the constant voltage rectifier.

• Journal of Advanced Marine Engineering and Technology
• /
• v.38 no.7
• /
• pp.916-922
• /
• 2014

Diode rectifiers have been widely used for an AC to DC converter. But a big problem is that they include large harmonics components in the input currents. A 12-pulse configuration with phase shifting transformer is useful for reducing them. however, it still includes the ($12{\pm}1$)th (m; integer) harmonics in the input currents. In this paper, we propose a single-phase square wave auxiliary voltage supply which is inserted in the middle DC bus. It reduces harmonics especially the 11th and 13th and the harmonic characteristic becomes almost equivalent to a 24-pulse rectifier. Theoretical analysis of the combined 12-pulse diode rectifier with the auxiliary supply is presented and a control method of the auxiliary supply is proposed. The reduction in the input current harmonics is verified by simulation using software PSIM.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.18 no.4
• /
• pp.360-364
• /
• 2012

AC to DC converter that consists of relatively simple diode rectifier devices has been widely used in the field of the electric propulsion system. Also, since this rectifier includes large harmonics in the input current, a variety of researches have been developed to reduce the harmonics. The proposed method of this paper is to reduce the harmonics included in the input current of rectifiers and propulsion motor by injecting the output current of diode rectifier into the input of them. In addition, the proposed method ensures electrical safety through the respective isolation of the injection current, the source, and the loads using the Wye-Delta insulating transformer applied in current injection device that is installed in the input circuit of rectifiers and propulsion motor. The proposed method is simulated by applying to the electric propulsion ship that is currently operating. We confirm the validity of the proposed method compared with conventional power conversion system.

• The Journal of Korean Institute of Information Technology
• /
• v.16 no.11
• /
• pp.23-34
• /
• 2018

This paper presents the high efficiency and high power-factor power supply for LED lighting equipment. The proposed power supply is the single-stage power structure consisted of the full-bridge diode rectifier and flyback converter, and thus the power-factor correction and output voltage regulation are performed simultaneously using only one controller IC and one power semiconductor switch. Furthermore, the proposed power supply reduces the voltage stress and switching loss of main switch using the regenerative snubber, and it improves the system efficiency using the synchronous rectifier. The applied synchronous rectifier is the new voltage-driven type and its operation and construction are simple. In this paper, the operation principle of proposed power supply is explained through the operation analyses of its power-factor correction and main power conversion parts and the operation of synchronous rectifier is described, briefly. Also, a design example of the power circuit of 40W-class prototype is shown and the operation characteristics of proposed power supply are validated through the experimental results of the implemented prototype by the designed circuit parameter.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.159-161
• /
• 2019

현재 단조용 유도가열 전원으로 사용되는 전류원 SCR 정류기 / 인버터는 입력단의 낮은 역률과 높은 THd를 갖는다. 이러한 단점들 때문에 최근 유도가열 전원장치로써 IGBT PWM 전류원 정류기 및 인버터회로가 연구되고 있다. 본 논문에서는 IGBT PWM 정류기 및 인버터의 제어회로를 제안하고 제어회로의 모델링을 통해 제어기를 설계하여 실험을 통해 그 성능을 검증하였다.