• 제목/요약/키워드: Air Gap

검색결과 1,449건 처리시간 0.025초

이격거리가 큰 전극의 공기 절연파괴에 영향을 미치는 인자측정에 관한연구 (A Study on the Measurements of Parameters Affecting the Breakdown Mechanism of a Large Air Spacing)

  • 조연옥;최영욱
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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    • pp.756-760
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    • 1988
  • The paper presents the measurement results on the parameters affecting the breakdown mechanism of a large air spacing under switching impulse voltages. Measured parameters are the velocities of leader channels, predischarge currents, electric charges injected into the rod-plane air gap and electric field intensities on the plane. For the 3m air gap under switching impulse voltages, the velocities of leader channel have been measured to be of 1cm/${\mu}s$ - 5cm/${\mu}s$, electric field intensity of 2kv/cm, predischarge current of 1.2A - 1.6A, the charges injected into the air gap of 11 - 40 ${\mu}$C for 400-887kV impulse voltages.

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엔탈피법을 이용한 원통형 몰드내에서의 상변화과정에 관한 연구 (A study on the phase change in the cylindrical mold by the enthalpy method)

  • 여문수;최상경;김문철
    • 설비공학논문집
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    • 제11권6호
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    • pp.891-897
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    • 1999
  • The heat transfer characteristics at the interface between the mold and the casting is one of the major factors for the solidification speed which determines the casting structures. The thermal resistance exists due to air gap formation at the mold/casting interface during the freezing process. In this study one dimensional Stefan problem with the air-gap resistance in the cylindrical mold is considered and the heat transfer characteristics is numerically examined by using the enthalpy method which is convenient in solving the Stefan problem with mushy zone. The present results agreed very well with those of previous papers. The effects of major parameters such as thermal conductivity, heat transfer coefficient of mold, on the thermal characteristics are investigated.

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이격거리가 큰 전국의 공기절연파괴 현상시 발생하는 인자측정에 관한 연구 (A Study on the Measurements of Discharge Parameters in Case of the Switching Impulse Breakdown of a Large Air Spacing)

  • 최영욱;조연옥
    • 대한전기학회논문지
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    • 제40권12호
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    • pp.1290-1295
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    • 1991
  • The paper presents the measurement results on the parameters affecting the breakdown mechanism of a large air spacing under switching impulse voltages. Measured parameters are the velocities of leader channels, predischarge currents, electric charges injected into the rod-plane air gap and electric field intensities on the plane. For the 3m air gap under switching impulse voltages, the velocities of leader channel have been measured to be of 1cm/x10S0-6Ts - 5cm/x10S0-6Ts, electric field intensity of 2kv/cm, predischarge current of 1.2-1.6A, the charges injected into the air gap of 11-40x10S0-6TC for 400-887kV impulse voltages.

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철도차량용 LIM의 공극변화에 따른 추력/수직력 특성 분석 (A study on thrust and normal force by air-gap variation of a linear induction motor used for an urban railway transit)

  • 양원진;박찬배;이형우;권삼영;박현준;원충연
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2008년도 추계학술대회 논문집
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    • pp.316-320
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    • 2008
  • A light rail transit, using a linear induction motor, is generally composed with reaction plates along railroad track and the three phase primary on the vehicle. This linear induction motor is driven to keep clearance between the primary and the secondary of the ground for preventing any contact. Therefore efficiency and power factor is very low. In addition, the reaction plate installed on the ground throughout entire railway is impossible to keep uniform gap and it may cause system deterioration. In this paper, A rotary-type small-scale model of a linear induction motor for various characteristic analysis is designed. Thrust force, normal force and input current of the model by air-gap variation have been analyzed by using a Finite Element Method (FEM). The effects of air-gap variation on system performance have been considered by analysis results.

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CFD를 이용한 핀의 열 사이에 간극을 가지는 Offset Strip Fin의 성능 해석 (CFD Analysis of Offset Strip Fin with a Gap between Rows)

  • 황성원;정지환
    • 설비공학논문집
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    • 제26권8호
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    • pp.381-387
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    • 2014
  • The off-set strip fins (OSF) have been widely used to construct plate-fin heat exchangers. Conventional OSF is constructed in successive rows of fins. New OSF structure is suggested to have a gap between adjacent rows of fins. The gap is intended to reduce fouling by allowing small objects to flow through fins. The objective of this work is to investigate the performance of off-set strip fins with gap between successive rows. Results showed that the performance of OSF with gap can't be predicted by previous correlation.

공극(기극(氣隙)) 변화에 따른 방사선촬영 선량평가 (An Assessment of the Radiation Dose from Radiography with the Change in Air Gap)

  • 안병주
    • 한국방사선학회논문지
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    • 제10권6호
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    • pp.381-385
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    • 2016
  • 본 연구에서는 공극 기법의 고관전압 촬영에서 격자를 사용한 것과 같은 화질을 유지하면서 선량을 줄이는 방안을 제안하고자 하였다. 실험은 초점과 수용체와의 거리 180 cm에서 공극을 10 cm, 15 cm, 20 cm, 25 cm, 30 cm으로 하였으며 각각의 공극 거리에서 관전류를 15 mAs로 고정하고 관전압은 80 KvP, 85 kVp, 90 kVp, 95 kVp, 100 kVp로 하여 촬영을 하였다. 전통적인 방법인 격자를 사용하였을 때 촬영은 초점과 수용체와의 거리 180 cm에서 15 mAs, 107 kVp로 하였다. 실험결과 격자를 사용하여 촬영하였을 때 표면선량은 0.130 R로 나타났고 공극을 20 cm로 하였을 때의 표면선량은 0.124 R로 나타났으며 두 영상 간의 PSNR은 10.65 [dB]로 나타났다. 결론적으로 표면선량이 적으면서 산란선을 제거하여 격자를 사용하였을 때와 유사한 화질을 유지할 수 있는 공극의 거리는 20 cm로 나타났다. 연구의 결과는 공극을 이용한 방사선촬영에서 표면선량을 제거할 수 있는 지표로 사용할 수 있을 것으로 사료된다. 결론적으로 표면선량이 적으면서 산란선을 제거하여 격자를 사용하였을 때와 유사한 화질을 유지할 수 있는 공극의 거리는 20 cm로 나타났다. 연구의 결과는 공극을 이용한 방사선촬영에서 표면선량을 절감할 수 있는 지표로 사용할 수 있을 것으로 사료된다.

흡음형 방음벽의 내부 구성에 따른 흡음특성 (Sound Absorbing Characteristics According to Interior Configuration of Noise Barrier)

  • 박진규;김상헌;김관주;박희준
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2003년도 춘계학술대회논문집
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    • pp.387-392
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    • 2003
  • This study is put a focus on the identification of sound characteristics according to the interior configuration of sound absorption material and air gap. Noise barrier is general consists of front perforated panel, air layer, sound absorption material, air gap and back plate. Noise barrier is required to the NRC value of 0.7. The absorbing performance of the noise barrier relies on the opening ratio of the perforated panel and the efficiency of the absorbing material. This study has observed the effect of opening ratio and hole size, the increase of sound absorbing performance by the configurations of sound absorption material and air gap. New designed noise barrier is achieved the acoustical performance of 0.87 the measurement in a reveration room.

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소형 비가열 실험을 이용한 원자로용기 외벽냉각시 용기와 단열재 사이의 자연순환 이상유동에 관한 연구 (A Non-Heating Small-Sclaed Experimental Study on the Two-Phase Natural Circulation Flow through an Annular Gap between Reactor Vessel and Insulation)

  • 하광순;박래준;조영로;김상백;김희동
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1927-1932
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    • 2004
  • A 1/21.6 scaled non-heating experimental facility was prepared utilizing the results of a scaling analysis to simulate the APR1400 reactor and insulation system. The behaviors of the air bubble-induced two-phase natural circulation flow in the insulation gap were observed, and the liquid mass flow rates driven by natural circulation loop were measured by varying the injected air flow rate and distribution. As the injected air flow rates increased, the natural circulation flow rates also increased. Both the longitudinal and the latitudinal distributions of the injected air affected the natural circulation flow rates, especially, the longitudinal effect is more larger.

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Performance of High-Speed 4/2 Switched Reluctance Motor

  • Lee, Dong-Hee;Ahn, Jin-Woo
    • Journal of Electrical Engineering and Technology
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    • 제6권5호
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    • pp.640-646
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    • 2011
  • The current study presents the design and performance of a novel 4/2 switched reluctance motor (SRM) for a high-speed air blower. With a comparative study of some rotor structures for a high-speed drive, a stepper-type rotor is optimized to produce a continuous torque and a low torque ripple. Rotor pole arc is modified to have a wide continuous output torque region, and air gap is determined to develop less torque ripple. The rotor radius is determined to reduce torque ripple with a reiterative FEM analysis. The designed rotor has three regions: short uniform, long uniform, and nonuniform air-gap region. The positive torque region is wider than a conventional 4/2 SRM without any torque dead zone. A prototype is tested and the efficiency is up to 72[%] at 30,000[rpm], 600[w] output.