• Title, Summary, Keyword: Electromagnetic field

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Short Circuit Electromagnetic Force Prediction by Coupled Electromagnetic-Mechanical Field Analysis of Dry-Type Transformer (전자계-기계계 결합해석에 의한 건식변압기의 단락강도 예측)

  • Ahn, Hyun-Mo;Hahn, Sung-Chin
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.2
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    • pp.301-308
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    • 2011
  • This paper deals with the coupled electromagnetic-mechanical field analysis for short-circuit electromagnetic force of the dry-type transformer. The short-circuit currents are calculated using external circuit in accordance with short-circuit test equipment. According to short-circuit current, the generated magnetic leakage flux density in dry-type transformer model is calculated by finite element method. The radially-directed electromagnetic forces in windings are calculated using electromagnetic field analysis and then axially-directed electromagnetic forces in windings are calculated using electromagnetic-mechanical field analysis. The calculated axially-directed electromagnetic forces in high voltage winding are compared to those of measured ones and showed good agreement with experimental results.

Characteristics and Measurement Method of the Underwater Electromagnetic Signature Emitted from a Naval Ship (함정 발생 수중 전자기장 신호의 특성 및 측정 기법)

  • Yang, Chang-Seob;Chung, Hyun-Ju;Shin, Seung-Je
    • Journal of the Korea Institute of Military Science and Technology
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    • v.9 no.2
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    • pp.11-19
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    • 2006
  • The underwater electromagnetic signatures of a naval ship are mainly generated from three sources which are the permanent and induced magnetic field in the ship's hull and other ferrous components, the cathodic current electromagnetic field established by the Impressed Current Cathodic Protection(ICCP) system or the Sacrificial Anode and the stray electromagnetic fields generated by onboard equipment. These signatures can be minimized by certain design methods or installation of signature reduction equipment. In this paper, we represented the characteristic of the underwater electromagnetic signature and the signature reduction techniques for a naval ship. Also, we measured the electromagnetic field changes emitted from the real ship using the Electric and Magnetic field Measurement System(EMMS). We found that the underwater electromagnetic signature for a naval ship can be used as input or trigger signal in a surveillance system and an influence mine.

The Effects of Pulsed Electromagnetic Field on Functional Recovery and Expression of GAP-43 after Incomplete Spinal Cord Injury in Rats (맥동전자장이 불완전 척수손상 흰쥐의 기능회복과 GAP-43의 발현에 미치는 영향)

  • Bang, Hyun-Soo
    • Journal of the Korean Society of Physical Medicine
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    • v.7 no.3
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    • pp.349-356
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    • 2012
  • Purpose : This study was designed to investigate the effects of pulsed electromagnetic field on functional recovery and expression of GAP-43 after incomplete spinal cord injury (SCI) in rats. Methods : To confirm the damage of SCI and effects of pulsed electromagnetic field, 20 Sprague-Dawley male rats were used and divided randomly 2groups (SCI, PEMF). Incomplete SCI was induced by using modified NYU drop model. After operation, functional recovery test, immunohistochemistry and western blot analysis were measured at 1, 2, 3 weeks. Pulsed electromagnetic field were apply three weeks (one times a day, five days a week and twenty minutes a session). Results : In the this study, applications of pulsed electromagnetic field after incomplete SCI induced the significant improvement in functional recovery and expression of neurotrophic factor. The results were as follows; Foot print test, PEMF were significantly decreased than the SCI (p<.05). Expression of GAP-43, PEMF were significantly increased than the SCI at 2 and 3 weeks (p<.05). Conclusion : In conclusion, pulsed electromagnetic field were positive effect in functional recovery and expression of GAP-43 after incomplete SCI in rats.

Reduction Characteristics of Electromagnetic Penetration through Narrow Slots in Conducting Screen

  • Park Eun-Jung;Kim Ki-Chai
    • Journal of electromagnetic engineering and science
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    • v.6 no.2
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    • pp.130-134
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    • 2006
  • This paper presents the reduction characteristics of penetrated electromagnetic fields through a narrow slot in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the parallel wire or parallel plate connected on the slot. The magnitude of penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot. An integral equation for the aperture electric field on narrow slots is derived and solved by applying Galerkin's method of moments. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by installing the parallel wire or parallel plate on the slot.

A Research on the Shielding of Injurious Electromagnetic Field for High-frequency Welder (고주파 웰딩기의 유해 전자파 차단에 관한 연구)

  • 장석용;심재형;김준안;백인환
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.447-450
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    • 2002
  • In the surrounding of the electric machinery and equipments occurring of using the electromagnetic fields, other electric machinery or equipments are induced the malfunctions by the radiated and leaked electromagnetic fields. And the human hazardous problems by that effect are being discussed frequently. So efficiently shielding technique of injurious electromagnetic field for high frequency welder is discussed in this paper.

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Assessment of Fuzzy Measure Possibility for the Electromagnetic Field according to Voltage fluctuation of the Jechon Area (제천지역 전압변동에 따른 전자계에 대한 퍼지척도 가능성 평가)

  • Kim, Sang-Chul
    • Journal of the Korean Society of Safety
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    • v.20 no.2
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    • pp.50-55
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    • 2005
  • This Paper Presents assessment of fuzzy measure Possibility far the electromagnetic field according to voltage fluctuation of the Jechon Area. To cope with substantial electromagnetic analysis, the safety assessment were analyzed the double 154kV T/L, 345kV T/L, Jechon-Ichon Jechon-Youngju, respectively. As the results of case study, in case of 345kV T/L, the electric field value was 11.4927kV/m, magnetic field value was 0.4622G at the Point about 7m away from the line in severest case. Tn assessment of fuzzy measure Possibility for the electromagnetic field, this paper use probability of fuzzy and measure of fuzziness technique.

Analysis of mechanical characteristics of superconducting field coil for 17 MW class high temperature superconducting synchronous motor

  • Kim, J.H.;Park, S.I.;Im, S.H.;Kim, H.M.
    • Progress in Superconductivity and Cryogenics
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    • v.15 no.3
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    • pp.13-19
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    • 2013
  • Superconducting field coils using a high-temperature superconducting (HTS) wires with high current density generate high magnetic field of 2 to 5 [T] and electromagnetic force (Lorentz force) acting on the superconducting field coils also become a very strong from the point of view of a mechanical characteristics. Because mechanical stress caused by these powerful electromagnetic force is one of the factors which worsens the critical current performance and structural characteristics of HTS wire, the mechanical stress analysis should be performed when designing the superconducting field coils. In this paper, as part of structural design of superconducting field coils for 17 MW class superconducting ship propulsion motor, mechanical stress acting on the superconducting field coils was analyzed and structural safety was also determined by the coupling analysis system that is consists of commercial electromagnetic field analysis program and structural analysis program.

Analysis of Electromagnetic Forming Using Sequential Electromagnetic-Mechanical Coupled Simulations (순차적 전자기-구조 연성해석을 통한 전자기성형 공정 해석)

  • Kim, J.;Noh, H.G.;Ko, S.J.;Kim, T.J.
    • Transactions of Materials Processing
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    • v.21 no.7
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    • pp.441-446
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    • 2012
  • A sequential coupled field analysis of electromagnetic free bulging was performed by using FEM. A 2D axi-symmetric electromagnetic model based on the magnetic vector potential is proposed for the calculation of magnetic field and Lorentz's forces. The Newmark integration method is used to calculate the transient dynamic plastic deformation of sheet during free bulging. In the finite element model, the effect of sheet deformation on the electromagnetic field analysis is taken into consideration. In order to confirm the sequential electromagnetic-mechanical coupling analysis, an experiment with an electromagnetic forming apparatus was conducted. The results showed that the final bulge height of the sheet predicted from the proposed method is in good agreement with experimentally measured height.

Characteristics of Specific Absorption Rate (SAR) in Electromagnetic (EM) Dosimetry

  • Hwang, Sun-Tae;Choi, Kil-Oung
    • Journal of Radiation Protection and Research
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    • v.25 no.2
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    • pp.109-114
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    • 2000
  • The SI unit of specific absorption rate (SAR) in W/kg in the electromagnetic (EM) field as non-ionizing radiation is exactly same as the SI unit of absorbed dose rate in Gy/s in the ionizing radiation field. The SI unit of both physical quantities can be expressed in $[m^{\cdot}s^{-3}]$. Where, the unit of absorbed dose, Gy stands for Gray. In EM biological interactions, the SAR equations are derived and the characteristics of EM field energy absorption in terms of the SAR are discussed and described on the mathematical basis.

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Reduction Characteristics of Electromagnetic Penetration through Narrow Slots in Conducting Screen by Loading Parallel Wire Arrays

  • Kim Ki-Chai;Lim Sung-Min
    • Journal of electromagnetic engineering and science
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    • v.6 no.2
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    • pp.123-129
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    • 2006
  • This paper presents a method of reducing penetration of penetrated electromagnetic fields through a narrow slot with parallel wire arrays in a planar conducting screen of infinite extent. An integral equation for the aperture electric field on the narrow slot is derived and solved by applying Galerkin's method of moments. When a plane wave is excited to the narrow slot, the aperture electric field is easily controlled by the parallel wire arrays connected on the slot and therefore the magnitude of the penetrated electric field is effectively reduced by loading the parallel wire arrays. The numerical results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by installing the parallel wire arrays on the slot. The results of the calculated penetration electric fields are in good agreement with that of the measured results.