• Fisheries and Aquatic Sciences
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• 제5권3호
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• pp.219-228
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• 2002

Based on the five-year (October 1992 through September 1997) Topex/Poseidon altimeter measurements, we describe the statistical characteristics of the eddy variability in the East Sea in terms of sea surface height anomaly, slope variability, and eddy kinetic energy (EKE). The sea surface height anomalies in the East Sea are produced with standard corrections from Topex/Poseidon measurements. In order to eliminate the high frequency noise in the sea surface height anomaly data, the alongtrack height anomaly data was filtered by about 40 km low-pass Lanczos filter based on Strub et al. (1997) and Kelly et a1. (1998). We find that there exists a distinct spatial contrast of high eddy variability in the south and low eddy energy in the north, bordering the Polar Front. In the northwestern area $(north\;of\;39^{\circ}N\;and\;west\;of\;133^{\circ}E)$ from the Polar Front where the eddies frequently appear, the EKE is also considerabel. The high kinetic energy in the southern East Sea reveals a close connection with the paths of the Tsushima Warm Current, suggesting that the high variability in the south is mainly generated by the baroclinic instability process of the Tsushima Warm Current. This finding is supported by other studies (Fu and Zlontnicki, 1989; Stammer, 1997) wh.ch have shown the strong eddy energy coupled in the major current system. The monthly variation of the EKE in both areas of high and low eddy variability shows a strong seasonality of a high eddy kinetic energy from October to February and a relatively low one from March to September. The sequential pattern of wind stress curl shows resemblance with those of monthly and seasonal EKE and the two sequences have a correlation of 0.82 and 0.67, respectively, providing an evidence that wind stress curl can be the possible forcing for the monthly and seasonal variation of the EKE in the East Sea. The seasonality of the EKE also seems to correlate with the seasonality of the Tsushima Warm Current. There also exists the large spatial and interannual variabilities in the EKE.

• 한국자기학회지
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• 제24권6호
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• pp.171-178
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• 2014

전자기를 이용하여 배관의 비파괴검사를 적용하는 방법 중 하나인 Remote Field Eddy Current Testing (RFECT)는 큰 마찰력이 발생하고 잔류자화성분이 남는 Magnetic Flux Leakage (MFL) 방식과 외벽의 결함을 측정하는데 곤란한 일반 Eddy Current Testing (ECT) 방식의 단점들을 보완할 수 있는 기법으로 50여 년 전부터 다양한 기관에서 연구되어왔다. 그러나 배관 내에서 발생하는 와전류와 자기장에 대한 연구와 RFECT Exciter Coil의 설계에 대한 논의가 부족한 실정이다. 본 논문에서는 유한요소법을 이용한 전자기 해석을 통해 배관 내에서 발생하는 와전류와 자기장의 분포를 확인하고 변수 변화에 따른 영향을 분석하였다. 또한 Exciter Coil에 대한 최적 설계 알고리즘을 제시하고, 결함 형상과 기타 변수 변화가 결함신호에 미치는 영향을 확인하였다.

• 비파괴검사학회지
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• 제18권6호
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• pp.464-476
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• 1998

원자력 발전소 증기발생기 전열관 검사에 사용되는 와전류 탐상에 있어 결함신호로부터 결함의 형상, 크기, 위치를 정확히 결정하는 것은 매우 중요한 문제 중의 하나이다. 이에 본 연구에서는 유한요소 해석으로 얻은 학습표본으로 훈련시킨 신경회로망을 이용해 이러한 와전류 결함신호의 역문제를 풀었다. 우선 4종류의 축대칭와 전류 결함신호를 총 216개 생성하고, 각각의 결함신호에 대해 24개씩의 와전류 특징을 추출한 후, 그 중에서 결함분석에 유용한 13개의 특징을 선택하였다. 그리고 이렇게 선별된 특징을 기반으로 4가지 형상의 결함에 대한 분류작업을 확률신경 회 로망에 의해 수행하고, 그 결과로 형상이 결정된 결함에 대한 크기산정을 역전파신경 회로망을 사용하여 실시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.397-400
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• 2001

In eddy, current brake system(BS), high current may flow for increase of braking force within a short time. Therefore, the estimation of thermal characteristics for BS is required. In this paper, the thermal characteristics of eddy-current brake for the Korean high speed train are analyzed by using 2-dimensional Finite Element Method (2D-FEM) and measured.

• 비파괴검사학회지
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• 제5권2호
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• pp.49-52
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• 1986

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3506-3511
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• 2007

The energy harvesting using smart materials has been extensively investigated to supply electric power to wireless sensor systems. In this paper, the energy harvesting using eddy current was studied with the integrated magnetic cantilever beam system. If a large conductive metal plate moves through a magnetic field which intersects perpendicularly to the sheet, the magnetic field will induce small rings of current which will actually create internal magnetic fields opposing the change. This eddy current that was induced in the coiled conductive sheet from the mechanical vibration was converted to chemical energy by charging batteries. The experimental results show that the eddy current generated the electric power up to max 31.2mW. Additionally the vibration reduction of the mechanical cantilever beam was observed by the energy dissipation in the electro-magnetic coupled system. The present result shows that the vibration level of the first natural frequency was reduced up to 7.7dB

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.820-821
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• 2008

본 논문은 FEA 기법을 이용하여 40kW급 HEV용 Traction 모터의 설계 및 고효율화를 위한 회전자 영구자석의 Eddy Current loss 저감 방안에 대한 연구를 수행하였다. 먼저 FEA 기법을 이용하여 40kW급 HEV용 Traction 모터 설계 및 특성해석을 수행하여 FEA 해석기법의 타당성을 확보하였다. 또한 Traction 모터의 손실 저감을 위해 magnet부분의 eddy current loss 저감방안에 대해 논하였으며, FEA 기법을 이용하여 회전자 magnet이 Solid, 1/2, 1/4, 1/14 segments로 나눈 타입에 따른 결과를 비교 분석하였다. 그 결과 magnet형태를 기존의 Solid 타입에서 14segments 타입으로 분할 시, magnet 내부의 current path가 줄어들어 eddy current loss가 가장 많이 저감됨을 알 수 있었으며, 이를 통해 HEV용 traction 모터의 고효율, 고성능화 설계방안을 도출 할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2274-2276
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• 1999

In this work, temperature rise and eddy current distribution on the enclosure and conductor of 3 pole gas insulated switchgear were investigated using analytical and experimental measures. The design of the diameters of the conductors and the enclosures of a meal clad gas insulated switchgear is primarily based on the insulation requirements. It is very difficult problem to predict the temperature rise of enclosed switchgear due to the complexity of the phenomena of heat transfer and existence of eddy current loss. To overcome this situations, we focused on the eddy current distribution on the enclosure of switchgear caused by high current 3 pole conductor as a fundamental basis. The experimental results about temperature distribution of 3 pole gas insulated switchgear were reported and measurements are compared with predictions of three-dimensional thermal model for eddy current analysis. As a result, three dimensional numerical analysis found to be in close relationship with experimental results and thermal model is efficient to predict the abnormal temperature rise in switchgear.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.625-629
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• 1998

So far a single-axis controlled repulsive type magnetic bearing system have been designed and fabricated in our laboratory employing the repulsive forces operating between the stator and rotor permanent magnet for levitation. The radial axis is uncontrolled passive one. The higher speed of operation is limited due to the vibration along the uncontrolled axis and the increase of control current due to eddy current interference. This paper will discuss a detailed modeling of the repulsive type magnetic bearing system for five axis control including the eddy current effect and the method of reduction of eddy current effect. Simulation results using Matlab will be presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.211-213
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• 1994

In tins paper, the method of analysis of induction heating is proposed. It's a coupled problem. First, eddy current problem with current source is analyzed using 2-D finite element method, from which eddy current distribution is obtained. And the second, heat source can be calculated directly by the eddy current. Also the temperature distribution is obtained using 2-D finite element method. Eddy current problem and heat transfer problem are dealt with under steady state in this paper.