• 제목/요약/키워드: stray field

검색결과 86건 처리시간 0.033초

직류급전계통에서의 레일전위 상승 분석 및 억제 방안 연구 (An Analysis on Rise of Rail Potential And A Study on Control Method for It in DC Feeding System)

  • 민명환;정호성;박영;김형철;신명철
    • 전기학회논문지
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    • 제60권3호
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    • pp.680-685
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    • 2011
  • Nowadays, in metropolitan railroad, DC feeding system is being generally applied. In order to reduce damages of electro-chemical corrosion caused by stray current and leakage current, in DC feeding system, rail is used as negative-polarity return conductor for traction load current. However, it has problem of rail potential increase and there are no adequate measures to prevent it in domestic. In this paper, we presented fundamental theory and related standards about rail potential increase. And then, we analyzed field testing data and simulated a variety of operations by using PSCAD/EMTDC as an analysis program of power system. In addition, voltage control device is suggested to prevent accidents caused by rail potential increase.

지하철의 표유전류에 대한 가스배관의 전식대책법 (The Corrosion Control Method for the Stray Current of Subway on Underground Gas Pipeline)

  • 하태현;이현구;배정효;김대경;하윤철
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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    • pp.382-384
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    • 2003
  • In case of parallel running with underground gas pipeline and subway, stray current of subway makes a interference on gas pipeline. This interference is one of the reason of gas pipeline corrosion. So, the high speed response rectifier was developed in order to mitigate a interference. In this paper, the field test result of proposed rectifier is presented. The effect of an alternative in stead of the forced drainage system is also presented.

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Development of Micro-size Search Coil Magnetometer for Magnetic Field Distribution Measurement

  • Ka, E.M.;Son, De-Rac
    • Journal of Magnetics
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    • 제13권1호
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    • pp.34-36
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    • 2008
  • For the measurement of the magnetic field distribution with high spatial resolution and high accuracy, the magnetic field sensing probe must be non-magnetic, but the MFM probe and sub-millimeter-meter size Hall probe use a ferromagnetic tip and block, respectively, to increase the sensitivity. To overcome this drawback, we developed a micro-size search coil magnetometer which consists of a single turn search coil, Terfenol-D actuator, scanning system, and control software. To reduce the noise generated by the stray ac magnetic field of the actuator driving coil, we employed an even function $\lambda$-H magnetostriction curve and lock-in technique. Using the developed magnetometer, we were able to measure the magnetic field distribution with a magnetic field resolution of 1 mT and spatial resolution of $0.1mm{\times}0.2mm$ at a coil vibration frequency of 1.8 kHz.

2차원 자기장에 의한 spin-valve 터널링 자기저항 소자의 자유층 반전 거동에 관한 연구 (Investigation on the Free Layer Switching behavior of a Spin-valve MTJ Device with 2 Dimensional Magnetic Field)

  • 이영우;김철기;김종오
    • 한국재료학회지
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    • 제13권6호
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    • pp.394-397
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    • 2003
  • MTJ devices are fabricated using metal shadow masks and switching characteristics are investigated under 2 dimensional magnetic field. When the hard axis field is less than $\pm$ 16 Oe, switching behavior is similar to that based on the Stoner-Wohlfarth model. As the hard axis field is larger than $\pm$ 16 Oe, deviation from the expectation by Stoner-Wohlfarth model is observed. These phenomena are induced by the generation of multi-domain and inhomogeneous magnetization reversal.

Calibration of ShadowCam

  • David Carl Humm;Mallory Janet Kinczyk;Scott Michael Brylow;Robert Vernon Wagner;Emerson Jacob Speyerer;Nicholas Michael Estes;Prasun Mahanti;Aaron Kyle Boyd;Mark Southwick Robinson
    • Journal of Astronomy and Space Sciences
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    • 제40권4호
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    • pp.173-197
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    • 2023
  • ShadowCam is a high-sensitivity, high-resolution imager provided by NASA for the Danuri (KPLO) lunar mission. ShadowCam calibration shows that it is well suited for its purpose, to image permanently shadowed regions (PSRs) that occur near the lunar poles. It is 205 times as sensitive as the Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC). The signal to noise ratio (SNR) is greater than 100 over a large part of the dynamic range, and the top of the dynamic range is high enough to accommodate most brighter PSR pixels. The optical performance is good enough to take full advantage of the 1.7 meter/pixel image scale, and calibrated images have uniform response. We describe some instrument artifacts that are amenable to future corrections, making it possible to improve performance further. Stray light control is very challenging for this mission. In many cases, ShadowCam can image shadowed areas with directly illuminated terrain in or near the field of view (FOV). We include thorough qualitative descriptions of circumstances under which lunar brightness levels far higher than the top of the dynamic range cause detector or stray light artifacts and the size and extent of the artifact signal under those circumstances.

표면 임피던스 경계조건을 이용한 몰드변압기 Tie-plate 손실 최소화에 관한 연구 (A Study on the Minimization of Tie-plate Loss of Cast Resin Transformer using Surface Impedance Boundary Condition)

  • 황성률;신판석
    • 전기학회논문지
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    • 제66권9호
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    • pp.1334-1340
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    • 2017
  • In this paper, a tie-plate shape is optimized by using the numerical technique to reduce the stray load loss of the tie-plate which is a mechanical structure for assembling and supporting of the transformer core. The eddy current loss of the structure is calculated by an electromagnetic field FEM program and the results are compared with 4 different shapes of tie-plates. Since the thickness of the tie-plate is very thin, and the skin depth is very small, the number of FE elements for 3-D transformer model is too big to solve. So, the surface impedance boundary condition (SIBC) is used to reduce the system matrix size and its computing time. To verify the method a 2.5 MVA 22,900/380V distribution transformer is simulated using one objective function and three design variables with some constraints. The final optimized tie-plate has three slots of 6 mm width and 23 mm gap, and the loss is reduced by 75 %. Consequently, the proposed algorithm seems to be considerably applicable to electric machinery as well as power transformer.

직류급전계통에서 레일전위상승제한장치의 동작제어기법 (A Control Technique for the Rail Potential Limit Device in DC Feeding System)

  • 민명환;정호성;박영;창상훈;신명철
    • 전기학회논문지
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    • 제61권3호
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    • pp.485-490
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    • 2012
  • Nowadays, in metropolitan railroad, DC feeding system is being generally applied. In order to reduce damage of electro-chemical corrosion caused by stray current and leakage current, in DC feeding system, rail is used as negative-polarity return conductor for traction load current. However, it has problem of rail potential increase and there are no adequate measures to prevent it in domestic. The rise of rail potential leads to damage for human and equipments. To solve the problems, this paper presents fundamental theory and related standards about rail potential increase. And then, we analyzed field testing data and simulated a variety of operations by using PSCAD/EMTDC as an analysis program of power system. In addition, this paper suggests rail potential limit device and addresses how to the device. To verify the effect, simulation of DC feeding system before and after the application of the device is carried out in various cases.

Metastable Vortex State of Perpendicular Magnetic Anisotropy Free Layer in Spin Transfer Torque Magnetic Tunneling Junctions

  • You, Chun-Yeol;Kim, Hyungsuk
    • Journal of Magnetics
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    • 제18권4호
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    • pp.380-385
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    • 2013
  • We find a metastable vortex state of the perpendicular magnetic anisotropy free layer in spin transfer torque magnetic tunneling junctions by using micromagnetic simulations. The metastable vortex state does not exist in a single layer, and it is only found in the trilayer structure with the perpendicular magnetic anisotropy polarizer layer. It is revealed that the physical origin is the non-uniform stray field from the polarizer layer.

Substrate-free Biosensing using Brownian Rotation of Bio-conjugated Magnetic Nanoparticles

  • Chung Seok-Hwan;Hoffmann Axel;Chen, Liaohai;Sun, Shouheng;Guslienko Konstantin;Grimsditch Marcos;Bader Samuel D.
    • Journal of Magnetics
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    • 제11권4호
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    • pp.189-194
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    • 2006
  • The recent development of bio-conjugated magnetic nanoparticles offers many opportunities for applications in the field of biomedicine. In particular, the use of magnetic nanoparticles for biosensing has generated widespread research efforts following the progress of various magnetic field sensors. Here we demonstrate substrate-free biosensing approaches based on the Brownian rotation of ferromagnetic nanoparticles suspended in liquids. The signal transduction is through the measurement of the magnetic ac susceptibility as a function of frequency, whose peak position changes due to the modification of the hydrodynamic radius of bio-conjugated magnetic nanoparticles upon binding to target bio-molecules. The advantage of this approach includes its relative simplicity and integrity compared to methods that use substrate-based stray-field detectors.