• 상하수도학회지
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• 제24권5호
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• pp.609-615
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• 2010

This study examined the change of water content in sludge using direct current electric equipment for decreasing the amount of sludge. The experiment showed that the average density of solids in the sludge treated by direct current before the centrifugal dewatering process was increased by 47.8%, when compared to those not treated by direct current. From the result of measuring the granularity of the sludge by the direct current treatment, that the average particle size of the sludge that was not exposed to the electric current was 52.36 ${\mu}m$, and more than 90% of the sludge was <94.29 ${\mu}m$ in size. On the other hand, the average particle size of the sludge passed through the direct current was 28.67 ${\mu}m$, and more than 90% of the sludge was 52.46 ${\mu}m$. This means that the average particle size of the sludge treated by the direct current was 45.2% smaller, and the standard deviation of granularity was improved. Because of water that separated from sludge moves to the (+) pole, larger particles become smaller and fine particles combine together, resulting in the equalization of the particle size. On the sludge after the centrifugal dehydrator, the change of the water content by the direct current was measured. The results showed that the average density of the solids was increased by 44.2% compared.

• 한국산학기술학회논문지
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• 제21권3호
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• pp.129-136
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• 2020

컷아웃스위치(COS: Cut Out Switch 이하 COS)는 전력계통에서 수용가로 전력을 송배전하기 위해 사용되는 변압기의 입력단에 설치되어 사고전류로부터 변압기를 보호하기 위해 설치되는 보호장치이다. COS는 크게 퓨즈링크와 COS몸체 및 접속부로 구성되어 사고전류시 퓨즈링크의 엘리먼트가 용단되어 사고전류를 차단하는 역할을 한다. COS 퓨즈링크가 용단되어 발생하는 강력한 아크가 화염과 소음을 유발시켜 주변지역 거주자에게 불쾌감 및 공포감을 주며, 아크화염으로 인하여 주변기기의 2차 피해를 유발시킬 수 있다. 본 논문에서는 COS 동작 시 발생되는 아크와 소음 및 보호협조의 문제점을 해결하기 위해 폭발형이 아닌 한류형 COS 퓨즈를 개발하였다. 또한 과전류 차단 기능이 없는 한류형 퓨즈의 단점을 개선하기 위해 퓨즈 엘리멘트, 스트라이커와 COS 퓨즈금구 개발을 통하여 과전류 차단성능의 신뢰성을 향상시켰다. COS의 동작 특성 향상은 퓨즈 엘리멘트의 최적 형상 도출, 스트라이커의 원활한 동작을 위한 동작선의 재질과 두께 및 저항 산정, 그리고 스트라이커와 연계된 하부금구류의 구조 개선을 통하여 수행하였다. 본 연구에서 개발한 COS 퓨즈링크는 공인기관의 시험을 통하여 차단성능과 보호협조 성능을 검증하였다. 시험은 본 연구의 한류형 COS와 기존의 폭발형 비한류형 COS의 비교 시험으로 수행하였다.

• 천문학회지
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• 제36권spc1호
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• pp.93-99
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• 2003

Various attempts have been made to explain the: pronounced seasonal and universal time (UT) variations of geomagnetic indices. As one of such attempts, we analyze the hourly-averaged auroral electroject indices obtained during the past 20 years. The AU and AL indices maximize during summer and equinoctial months, respectively. By normalizing the contribution of the solar conductivity enhancement to the AU index, or to the eastward electrojet, it is found that the AU also follows the same semiannual variation pattern of the AL index, suggesting that the electric field is the main modulator of the semiannual magnetic variation. The fact that the variation pattern of the yearly-mean AU index follows the mirror image of the AL index provides another indication that the electric field is the main modulator of magnetic disturbance. The pronounced UT variations of the auroral electrojet indices are also noted. To determine the magnetic activity dependence, the probability of recording a given activity level of AU and AL during each UT is examined. The UT variation of the AL index, thus obtained, shows a maximum at around 1200-1800 UT and a minimum around 0000-0800 UT particularly during winter. It is closely associated with the rotation of the geomagnetic pole around the rotational axis, which results in the change of the solar-originated ionospheric conductivity distribution over the polar region. On the other hand the UT variation is prominent during disturbed periods, indicating that the latitudinal mismatch between the AE stations and the auroral electrojet belt is responsible for it. Although not as prominent as the AL index, the probability distribution of the AU also shows two UT peaks. We confirm that the Dst index shows more prominent seasonal variation than the AE indices. However, the UT variation of the Dst index is only noticeable during the main phase of a magnetic storm. It is a combined result of the uneven distribution of the Dst stations and frequent developments of the partial ring current and substorm wedge current preferentially during the main phase.

• 한국정밀공학회지
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• 제24권9호
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• pp.95-102
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• 2007

The scanning electron microscope (SEM) is one of the most popular instruments available for the measurement and analysis of the micro/nano structures. It is equipped with an electron optical system that consists of an electron beam source, magnetic lenses, apertures, deflection coils, and a detector. The magnetic lenses playa role in refracting electron beams to obtain a focused spot using the magnetic field driven by an electric current from a coil. A SEM column usually contains two condenser lenses and an objective lens. The condenser lenses generate a magnetic field that forces the electron beams to form crossovers at desired locations. The objective lens then focuses the electron beams on the specimen. The present work concerns finite element analysis for the electron magnetic lenses so as to analyze their magnetic characteristics. To improve the performance of the magnetic lenses, the effect of the excitation current and pole-piece design on the amount of resulting magnetic fields and their peak locations are analyzed through the finite element analysis.

• 제어로봇시스템학회논문지
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• 제21권2호
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• pp.137-144
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• 2015

In hybrid or electric vehicles, the hydraulic brake system must be controlled cooperatively with the traction motor for regenerative braking. Recently, a motor driven brake system with a PMSM (Permanent Magnet Synchronous Motor) has replaced conventional vacuum boosters to increase regenerative power. Unlike industry motor controls, additional source codes such as functional safety are essential in automotive applications to meet ISO26262 standards. Therefore, the control logic execution time increases, which also causes an extension of the motor current control period. The increased current control period makes precise motor current control challenging inhigh speed ranges where the motor is driven by high frequency. In this paper, a PWM update strategy and a time delay compensation method are suggested to improve current control and system performance. The proposed methods are experimentally verified.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2284-2291
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• 2018

This paper deals with optimum design of surface mounted permanent magnet synchronous motor (SPMSM) for automotive component. For a compact system structure, it was designed as a motor with a 14-pole 12-slot concentrated winding and hollow shaft. The motor is a thin type structure which stator outer diameter is relatively large compared to its axial length and is designed to have a high magnetic saturation for increasing the torque density. Since the high magnetic saturation in the stator core increases the axial leakage flux, a 3-dimensional (3-D) finite element analysis (FEA) is indispensable for torque analysis. However, optimum designs using 3-D FEA is inefficient in terms of time and cost. Therefore, equivalent 2-D FEA which is able to consider axial leakage flux is applied to the optimization to overcome the disadvantages of 3-D FEA. The structure for cost reduction is proposed and optimum design using equivalent 2-D FEA has been performed.

• 한국안전학회지
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• 제30권5호
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• pp.14-19
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• 2015

This study performed simulation tests to prevent induced lightning that occurs to a 22.9 kV-Y distribution line. A simulated distribution line reduced to 1/50 of an actual distribution line was installed to measure the induced voltage according to the change in grounding resistance. It was found that the induced voltage increased as the grounding resistance increased but that the range of its increase was small. This study examined the reliability of the proposed lightning preventive distribution line using the Minitab program (Minitab 17). When a grounding resistance of $300{\Omega}$ was maintained for each electric pole, the Anderson Darling (AD) was 0.410, the smallest, and the P value was analyzed to be 0.323, verifying that the reliability and stability were excellent. Therefore, these results will be utilized as a basis for the substantiation of a lightning preventive distribution line before its installation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.275-277
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• 2005

In a lithium-ion battery which is being used in many portable electronic goods, electrolyte is disaggregated and then the gas is happened when electric charging volt is over the 4.5V. So, the pressure on the safety valve is increased and electrolyte is leaked out in the cell. It leads to the risk of explosion. On the other hand, in the case which the battery is discharged excessively, the negative pole is damaged and the performance of the battery is deteriorated. The protection module of a lithium-ion battery is used for preventing such risk and the inspection system is needed to check the performance of such protection module. In this research, a PC-based auto inspection system is developed for the inspection of a battery protection module using Dallas chipset. In the inspection system, AVRl28 chip is used as a controller and the communication protocol is developed for the data communication between the protection module and the AVR128 chip. And GPIB interface is used for the control of measuring devices. Also, MMI environment is developed using LabView for convenient monitoring by the tester.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.535-538
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• 2006

The coastline of the Choa Phraya Rivermouth in the Upper Gulf of Thailand has been changed drastically. The western side especially at Ban Laem Sing was eroded for 400 meter in 26 years or with the rate of 15 meter per year on the average. The Metropolitan Electricity Authority has granted five years research project to us to study the efficiency of the electric pole fence as a mean to reduce the wave force and increase sedimentation rate inside for mangrove replantation. If the method works efficiently, it will be used to reclaim the coastal land loss in other areas in Thailand. The project was done since 2005 after the fence was constructed completely in October 2005. The oceanographic surveys were conducted before and after the construction in northeast monsoon season to study the impact of physical oceanographic forces on the coastline change. The sedimentation rates were measured each month. It is rather low about 2 cm/month. The subsiding rate from the load of deltaic sediment and groundwater withdraw using boring data is about 30 mm/year. The cumulative sinking rate is 55.8 cm from 1978 to 1995. We have tried to design the method of mangrove plantation in this area. The remote sensing data such as LANDSAT and aerial photos from 1987 to 2002 for 15 years were used to compute the rate of coastline change at each 50 m section along the western side of the rivermouth.

• 한국태양에너지학회 논문집
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• 제24권2호
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• pp.51-62
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• 2004

Architects may evaluate building models to see how a building will shadow itself and its neighbors at various times. A heliodon, a tilt-table which is a machine that imitates the rotation and orbit of the Earth, helps architects wanting to analyze patterns of shadow patch, passive solar heating options, site solar panels, or control solar heat gain. The heliodon swivels in three directions for setting latitude, season, and time of day. Using the device, an architect first clamps a model to the tabletop, then turns the table to the coordinates of interest. Usually, the winter and summer solstices receive strong attention, for they represent extreme cases, A more recent installation at a university adds to its heliodon a set of lamps to recreate the illumination level and more accurate patterns of shadow patch. The table holds the building model at various angles to a spotlight, which mounts in the pole. The set of scale model measurement describes the validity of various electric lamps as an artificial sun to approximate the sun's parallel rays, helping designers to distinguish between illuminated areas in and around a building and those regions falling in the shadows.