• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1445-1456
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• 2011

부산도시철도 추진장치를 종합 제어하는 Chopper Gate Control Unit는 다수의 전자 전기부품, PCB, 전원공급기, 게이트회로증폭기, 프레온가스냉각기, 보호회로 등으로 구성되어 있는 주요장치로서 일본 미씨비시에서 생산된 제품을 사용하고 있다. 최근에는 초퍼장치의 고장 및 시험기 에러가 자주 발생하여 원인분석 결과 Chopper Gate Control Unit內 LPF(Lower Pass Filter)의 장기사용(약25년)으로 인한 노후화와 성능저하가 주요 원인이었음을 밝혀내고 물품구매를 위해 제작사에 문의 하였으나 이미 생산이 중단된 제품으로 별도 주문 제작시에는 고가의 비용이 발생한다. LPF는 몰딩처리가 되어있는 부품으로 수선이 불가하여 자체기술력으로 연구 개발하여 현재 부산도시철도 1호선 전동차에 13set를 적용하여 운영하고 있다. 본 논문에서는 연산 증폭기(OP Amp)와 저항, 콘덴서 등의 조합으로 자체개발한 능동필터인 Active LPF의 특성분석, 회로해석 및 설계, 다기능분석기, 스펙트럼분석기, 오실로스코프 등을 이용한 파형특성과 PS Pice 시뮬레이션 시험결과 등 개발에 관한 연구내용을 다루었다.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1700-1711
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• 2015

In the last decade it has been witnessed significant developments in the area of nano particles and nano scale fillers on electrical, thermal, and mechanical properties of polymeric materials such as resins, varnishes, enamel and bakelites. The electric and thermal properties were more important in the electrical equipments for both steady state and transient state conditions. This paper deals with the characterization of the electric and thermal properties of the pure varnish and zirconia (ZrO₂) filler mixed varnish. The electric properties such as dielectric loss (tan δ), dielectric constant (ε), dielectric strength and partial discharge voltage were analyzed and detailed for different samples. It was observed that zirconia nano filler mixed varnish has the superior dielectric and thermal properties when compared to those of standard varnish. It has shown that at power frequency the 1wt% nano composite sample has the higher permittivity value when compared to other samples. It has been examined that the 1wt% sample was having higher inception and extinction voltages when compared to other samples. It has been observed that 1wt% sample has higher dielectric strength when compared with other samples. There has been an improvement of thermal property by adding few weight percent of zirconia nano fillers. There was not much variation in glass transition among the nano mixed composites. The weight loss was improved at 1wt% of the zirconia nano fillers.

• 한국산업융합학회 논문집
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• 제26권1호
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• pp.175-181
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• 2023

In offshore plants, various equipments including cranes and davits are used for safety management. Hydraulic cylinder type actuators are mainly used for luffing operations such as cranes and davits. However, in the case of a cylinder using hydraulic pressure, a separate power pack is required to supply hydraulic pressure. When used for a long time, maintenance costs such as sticking of hydraulic valves, contamination of hydraulic oil and deterioration of hydraulic hoses occur. In addition, a lot of hydraulic oil is used in the handling of cranes and davits, which causes marine pollution due to management problems. As a result, as interest in marine pollution prevention has increased recently, interest in actuators that do not use hydraulic pressure is also increasing. Therefore, in this study, we intend to develop a davit with an electric cylinder type actuator that uses electricity rather than hydraulic pressure by the SOLAS regulation. In other words, the conceptual design of the davit driven through the linear motion of the ball screw using electricity is performed, and the structural safety of the drive is also reviewed so that it can be utilized in the industrial field.

• 전자공학회논문지
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• 제52권7호
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• pp.135-142
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• 2015

인체 구동 방식의 자가 발전기는 외부 환경에 덜 의존한다는 장점 덕분에 비상용 혹은 야외 활동 중의 소규모 전력 공급원으로 주목 받고 있다. 하지만 대부분의 자가 발전기는 전자기 유도 결합의 효율이 높지 않아 출력이 미미하며, 특정 부위의 근육만을 지속적으로 사용하는 단조로운 구동 방식을 택하고 있어, 사용 중에 쉽게 지루해질 뿐만 아니라 근피로가 쉽게 누적되어 실제 원하는 출력을 얻을 만큼 충분한 시간 동안 구동하는 것이 거의 불가능하다. 이러한 낮은 효율과 사용성의 문제로 인해 인체 구동 방식의 자가발전기가 실생활에서 사용되는 빈도는 높지 않다. 본 연구에서는 전자기 유도 효율이 높은 종축 결합 방식의 발전 장치를 간단한 구조로 구현하여 출력을 높이는 동시에, 자성체의 운동 관성에 의한 가속이 가능한 인체 구동 방식의 발전기를 설계 제작하였다. 개발된 발전기와 기존 상용 자가 발전기와의 비교 실험을 통해 높은 출력 뿐 아니라 장시간 구동이 가능함을 검증하였다. 아울러 인체 구동 발전기에서 실질적으로 중요한 요소임에도 불구하고 기존 연구에서 제시된 바 없는 인체의 투입 에너지를 실증적으로 파악하기 위해 호흡 가스 기반의 실제 운동 대사량 측정법에 근거한 실험을 시행하여 자가 발전기의 운동 부하를 추정하였다. 향후 성능 개선과 휴대성 증진을 통해 모바일 기기의 전력 지속 문제를 해결하는 데 기여할 수 있을 것으로 기대한다.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.263-269
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• 1996

In indian agricultural , the energy use pattern has played dominant role in influencing the level of mechanization . Besides that the agro-climatic factors as well as the size of holdings do affect the degree of mechanization . Nearly 30 percent of total cultivated area is owned by l76 percent of the small and tiny land holders each owning even less than a hectare. On the other hand, about 2 percent of land owners cultivate land. These variabilitieshave greatly influenced the ownership of power sources on Indian farms. Small farmers, employ human and animal energies with the use of hand tools and animal drawn equipments. Whereases, the use of tractors, power tillers, electric motors, etc. on small farms is on a marginal scale. There are few pockets and also extensive wheat growing regions where mechanical and electrical power sources are extensively used in production agriculture leading to about 185% of cropping intensity . In that region, the animal energy is employed for on the farm transport of fertilizers, fodders and fuel to support milch animals and other household activities . Inspite of high degree of mechanization, the harvesting of crops is done by human labour with few exceptions of harvesting wheat crops by combines in few pockets. In overall assessment of mechanization, the following conclusions are drawn : ⅰ) Farm operation which show a growing trend of mechanization are (a) tillge, (b) seedling (c) Irrigation (d) Plant protection application (e) Threshing and (f) Transport . ⅱ) Crop cultivation system in respect of wheat, maize and sorghum have been greatly mechanized. ⅲ) The least mechanized cropping systems are (a) vegetable production and (b) cultivation of sugarcane, cotton, rice and pulses. ⅳ) Annual production of tractor has touched the figure of 280.000 by 1995 and the total number has crossed 1.5million on Indian farms.

• 전기학회논문지
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• 제62권10호
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• pp.1368-1375
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• 2013

The Smart Grid, which can monitor or diagnose the power grid in real time to operate efficiently, has been pushed ahead systematically as one of alternatives to solve these issues by combining the advanced Information Communication Technology and the electrical network. Hence, the electric company which introduces smart grid technology can read remotely the electrical meter readings by means of two-way communication between the meter and the central system. This enabled the customer and the utility to take part in reasonable electrical energy utilization. AMI became one of the core foundations in realizing the Smart Grid. It is hard to test the entire process of AMI system before the full deployment because it covers the broad objects from the customer to the utility operation system and requires mass data handling and management. Therefore, we design an efficient AMI network model and a simulator for performance evaluation required to simulate the network model similar to the real environment. This tool supports to evaluate the efficiency of the AMI network equipments and deployment. Additionally, it estimates the appropriate number of deployments and the proper capabilities.

• 한국안전학회지
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• 제33권3호
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• pp.27-32
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• 2018

Nowadays, to prevent electrical accidents in Korea, inspectors directly performed checking general electrical facilities as a cycle from every one to three years. It is difficult to presuppose an omen because intact conditions of electrical equipments are not kept at the time of inspection. In this paper, in order to ensure effectiveness of an online basis electric inspection, we developed an electrical safety IoT system using LoRa communication technology to enable monitoring mainly electrical safety components such as overcurrent, overvoltage, resistive leakage current, and power. Then we proposed a method for verifying performances of the prosed electrical safety IoT system. Resistive leakage currents are calculated by using difference of phase between voltages and currents. We verified that average errors are 0.97%, which reference goal is ${\pm}5%$ for a device, through reliability test according to conditions. Results of this research can be used as basic study materials to develop technologies for measuring three phase leakage current and for implementing public electrical safety. platform.

• 한국태양에너지학회 논문집
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• 제37권6호
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• pp.39-49
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• 2017

Pool boiling, one of the key thermal-hydraulics phenomena, has been widely studied for improving heat transfer efficiencies and safety of nuclear power plants, refrigerating systems, solar-collector heat pipes, and other facilities and equipments. In the present study, the critical heat flux (CHF) and heat-transfer coefficients were tested under the pool-boiling state using graphene M-5 and M-15 nanofluids as well as oxidized graphene M-5 nanofluid. The results showed that the highest CHF increase for both graphene M-5 and M-15 was at the 0.01% volume fraction and, moreover, that the CHF-increase ratio for small-diameter graphene M-5 was higher than that for large-diameter graphene M-15. Also at the 0.01% volume fraction, the oxidized graphene M-5 nanofluid showed a 41.82%-higher CHF-increase ratio and a 26.7%-higher heat-transfer coefficient relative to the same nanofluid without oxidation treatment at the excess temperature where the CHF of distilled water occurs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1864-1866
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• 1996

Grounding is the art of making an electrical connection to the earth. In order to protect man, electrical and/or electric equipments from the lightning strokes, all the energy of lightning strokes must be diverted via a safe path to earth. It is essential to the transient grounding resistance against lightning strokes. In this paper, measurements and analyses of grounding surge impedance have been investigated. For measurements of grounding surge impedance the pulse generator was designed and fabricated. The pulse generator has rise time of 22.4 ns and pulse duration of $8\;{\mu}s$. The transient grounding resistance has been measuring by injecting low power and step current between the earthing system under test and a remote reference earth and measuring the potential rise caused by this current. As a result, the transient grounding resistance against lightning surge in the short time domain is much higher than steady state grounding resistance.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.648-655
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• 1999

In this study, a relationship between DC discharge and the radiated electromagnetic waves is investigated by measuring electromagnetic waves using a biconical antenna and a spectrum analyzer. The characteristics of frequency spectrum ofthe radiated electromagnetic waves was measured at the atmospheric pressure in Liquid Nitrogen $(LN_2)$ during partial discharges in nonuniform and uniform electric field depend on positive DC power. From this experiment results, it was confirmed that when partial discharge was produced in Liquid Nitrogen and Air, the signal of partial discharge was detected by this experiment and the analysis method. It is considered thatthese results obtained from this investigation may be used as fundamental data for diagnosis and prediction of insulation on the equipments ultra-high voltage, superconducting and cryogenic applications.