• Title/Summary/Keyword: high flowing

검색결과 670건 처리시간 0.024초

식물성절연유의 유동속도와 온도에 따른 절연파괴전압 (Dielectric Breakdown Voltage According to Flow Velocity and Temperature of Vegetable Oils)

  • 최순호;허창수
    • 전기학회논문지
    • /
    • 제61권6호
    • /
    • pp.821-826
    • /
    • 2012
  • The streaming electrification process of vegetable insulating oils occurring when the oils contacted with solid material in a high power transformer circulation system seems to cause electrical discharge incidents and may cause failures. We therefore measured the dielectric breakdown voltage tendency of vegetable insulating oils flowing on the surface of the charging device with various velocity and temperature. First, the relation between the velocity and breakdown voltage tendency of vegetable oils, can be explained by volume effect and v-t effect. Second, experimental results show that applied voltage have little effect on dielectric breakdown voltage, when vegetable insulating oils used for large power transformer.

고전력 응용을 위한 소프트 스위칭 위상 천이 PWM 풀 브리지 컨버터 (Soft-Switching Phase-shifted PWM Full-bridge Converter for high power applications)

  • 김영필;김태웅;한완옥;이성백
    • 한국조명전기설비학회:학술대회논문집
    • /
    • 한국조명전기설비학회 2000년도 학술대회논문집
    • /
    • pp.188-192
    • /
    • 2000
  • This paper presents a novel prototype of soft-switching PWM Full-bridge converter which incorporates active power switches in series with each rectifier diode in transformer secondary side. Switching and conduction losses of all the switches and devices are reduced as well as commutating current and circulating current flowing through transformer as compared with conventional converter. And duty ratio of primary switches is constant for maximum voltage conversion ratio. But this converter can be varied output by duty ratio of secondary switches. Operation principles basically the same as that of the PWM Full-bridge converter published previously. The operating characteristics of this converter are illustrate and discussed including the simulated analysis.

  • PDF

저온수열원이용 열펌프시스템의 전처리 및 성능분석 (Performance Analysis and Prior-Treatment of Heat Pump System with Low-Temperature Water Heat Source)

  • 박성룡;장기창;이상남;라호상;박준택
    • 대한기계학회:학술대회논문집
    • /
    • 대한기계학회 2000년도 춘계학술대회논문집B
    • /
    • pp.258-263
    • /
    • 2000
  • River water is higher in temperature than the surrounding environment during the winter. It is highly suitable a heat source for heat pump system. Despite its suitability, however, it is not widely used, due to its fouling and corrosive nature in heat exchanger tubes of evaporator. It is designed prior-treatment system which come into direct contact with the river water, such as auto-seamer, ozone generator for bactericidal test and auto-cleaning system. And it is analyzed treatment effects for its operation. It is designed two-stage compression heat pump system using R-134a with heating load 35.16kW, ad analyzed its performance. As a result it is obtained 3.08 COP when mid-point pressure is 1,200kPa, and bypass ratio of flowing refreigerant to high-stage compressor is 25.1%

  • PDF

A New Sustain Driving Method for AC PDP : Charge-Controlled Driving Method

  • Kim, Joon-Yub
    • KIEE International Transactions on Electrophysics and Applications
    • /
    • 제2C권6호
    • /
    • pp.292-296
    • /
    • 2002
  • A new sustain driving method for the AC PDP is presented. In this driving method, the voltage source is connected to a storage capacitor, this storage capacitor charges an intermediate capacitor through LC resonance, and the panel is charged from the intermediate capacitor indirectly. In this way, the current flowing into the AC PDP when the sustain discharge occurs is reduced because the current is indirectly supplied from a capacitor, a limited source of charge. Thus, the input power to the output luminance efficiency is improved. Since the voltage supplied to the storage capacitor is doubled through LC resonance, this method call drive an AC PDP with a voltage source of about half of the voltage necessary in the conventional driving methods. The experiments showed that this charge-controlled driving method could drive ail AC PDP with a voltage source of as low as 107V. Using a panel of the conventional structure, luminous efficiency of 1.28 lm/W was achieved.

절연유의 전기전도에 미치는 첨가제의 영향 (The Effect of Additive on the Electric conductivity of Insulating Oil)

  • 정광현;김영봉;김용운;임헌찬;이덕출
    • 한국전기전자재료학회:학술대회논문집
    • /
    • 한국전기전자재료학회 1996년도 춘계학술대회 논문집
    • /
    • pp.158-161
    • /
    • 1996
  • The static charges are generated by streaming electrification phenomena in insulating oil flowing by force for the purpose of cooling at the internal of Ultra-high power transformer. In this thesis, their elimination method was studied. In this paper the effect of Additive on the electric conductivity of Insulating oil is studied. The variation of electric conductivity disappear when Additive is molten in insulating oil BTA(Benzotriazole) appear more variation of electric conductivity than that of SP-S10(Sorbitan mono-stearate). But the variation is not enough to decrease streaming electrification of insulating oil($\sigma$>10$\^$-12/[S/cm]).

  • PDF

프로판 층류확산화염의 그을음 천이에 대한 형태학적 연구 (Morphological Study on the Soot Transition in a Propane/Air Laminar Diffusion Flame)

  • 심성훈;유창종;신현동
    • 한국연소학회지
    • /
    • 제7권2호
    • /
    • pp.24-33
    • /
    • 2002
  • The morphology of deposits on $15-{\mu}m$ thin SiC filaments has been investigated with SEM in a co-flowing, propane/air laminar diffusion flame. The average size of mature soot particles deposited in the luminous flame edge is strongly dependent on their axial position in a typical heavily sooting flame. The surface growth of liquid-phase PAHs molecules and the transition to soots from fully-developed precursors could be observed in the radial deposition of the flame. Two sooting regimes were found: one is the transition from the condensed-phase precursors; the other is the aggregation of smaller soot particles (or chains of them) to be carried along particle path lines. In the high temperature flame edge outside the soot luminous flame surface, the very thin fiber-like structures, which are about 10 nm thick, were found.

  • PDF

캐스캐이드 냉동시스템에서 냉매로서의 프로판-에탄 냉매의 성능 분석 (The Characteristic of Propane(R290)-Ethane(R170) as Refrigerant in the Cascade Refrigeration System)

  • 김필환;이병호;정효민;정한식;김철수
    • 동력기계공학회지
    • /
    • 제11권4호
    • /
    • pp.50-55
    • /
    • 2007
  • Nowadays, demands on super low temperature condition for industrial and commercial uses are thriving. Considering of its wide application in the present and the future, study of the super-low temperature refrigeration system should be actively carried out. This study is aimed to investigate refrigeration capacity and coefficient of performance(COP) of the cascade refrigeration system, as well as to get the system which can reach evaporator temperature of $-70^{\circ}C$. For this purpose, R290 and R170 are charged in high stage and low stage respectively. Finally the characteristics of system using R290 and R170 will be proposed. Additionally, In this experiment, the flow rate of air flowing through the LS evaporator and the compressor inlet pressure were varied to investigate the refrigeration capacity and coefficient of performance characteristics.

  • PDF

Concentration distributions during flow of confined flowing polymer solutions at finite concentration: slit and grooved channel

  • Hernandez-Ortiz, Juan P.;Ma, Hong-Bo;de Pablo, Juan J.;Graham, Michael D.
    • Korea-Australia Rheology Journal
    • /
    • 제20권3호
    • /
    • pp.143-152
    • /
    • 2008
  • Simulations of solutions of flexible polymer molecules during flow in simple or complex confined geometries are performed. Concentrations from ultradilute up to near the overlap concentration are considered. As concentration increases, the hydrodynamic migration effects observed in dilute solution unidirectional flows (Couette flow, Poiseuille flow) become less prominent, virtually vanishing as the overlap concentration is approached. In a grooved channel geometry, the groove is almost completely depleted of polymer chains at high Weissenberg number in the dilute limit, but at finite concentration this depletion effect is dramatically reduced. Only upon inclusion of hydrodynamic interactions can these phenomena be properly captured.

월류흐름을 포함한 부정류 계산모형에 관한 연구 (A Study on Unsteady Flow Model Including Weir Flow Simulation)

  • 전경수
    • 물과 미래
    • /
    • 제29권2호
    • /
    • pp.153-165
    • /
    • 1996
  • 월류흐름을 포함하는 1차원 부정류 계산모형으로서 월류흐름에 대한 국소적 처리기법을 포함한 단일하도 모형 및 폐합형 수계에 모형을 각각 구성하여, 월류부를 포함한 시험하도 문제에 적용함으로써 모형의 적용성을 조사하였다. 역방향 흐름을 포함한 다양한 형태의 월류흐름이 잘 모의되었으며, 월류구조물의 표고가 높아서 실질적으로 흐름이 존재하지 않는 경우도 성공적으로 모의되었다. 자유월류형 역방향 흐름은 폐합형 모형에 의해서 뿐만 아니라 단일하도 모형에 의해서도 모의될 수 있음이 입증되었다.

  • PDF

강릉 운산충적평야의 홀로세 후기의 환경변화와 지형발달 (The Environmental Change and Geomorphic Development of Unsan Alluvial Plain in Kangreung City during the Late Holocene)

  • 윤순옥
    • 대한지리학회지
    • /
    • 제33권2호
    • /
    • pp.127-142
    • /
    • 1998
  • Unsan alluvial plain is the backmarsh of Seomseokcheon which is a river originated from Chilseongdae(954m) on Mts Taeback, flowing into Donghae in southern Kangreung City, Kangwon Province. The vegetation change, geomorphic develoopment and depositional environment during the late Holocene have been investigated, using the methods such as boring, pollen analysis and radiocarbon dating. Because the deposits fo the study area are mainly consisted of peat and paety sand, they contained many pollen fossils. The peat layer has been sedimented since the high sea-level periods, 3,200 y. BP, and the records of vegetation change until now has well preserved here. According to archeological researches and the results of pollen analysis in east coast of Korea, it is supposed that the prehistoric rice farming in this area has begun since ca. 1,800 y. BP.

  • PDF