• Title/Summary/Keyword: Electromagnetics

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Application of wavelet transform in electromagnetics (Wavelet 변환의 전자기학적 응용)

  • Hyeongdong Kim
    • Journal of the Korean Institute of Telematics and Electronics A
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    • v.32A no.9
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    • pp.1244-1249
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    • 1995
  • Wavelet transform technique is applied to two important electromagnetic problems:1) to analyze the frequency-domain radar echo from finite-size targets and 2) to the integral solution of two- dimensional electromagnetic scattering problems. Since the frequency- domain radar echo consists of both small-scale natural resonances and large-scale scattering center information, the multiresolution property of the wavelet transform is well suited for analyzing such ulti-scale signals. Wavelet analysis examples of backscattered data from an open- ended waveguide cavity are presented. The different scattering mechanisms are clearly resolved in the wavelet-domain representation. In the wavelet transform domain, the moment method impedance matrix becomes sparse and sparse matrix algorithms can be utilized to solve the resulting matrix equationl. Using the fast wavelet transform in conjunction with the conjugate gradient method, we present the time performance for the solution of a dihedral corner reflector. The total computational time is found to be reduced.

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A study on Dynamic Characteristics of an Eddy Current Damping (와전류감쇠기의 동특성에 관한 연구)

  • Park, Jungsam;Bae, Jaesung;Hwang, Jaihyuk;Kang, Kukjeong
    • Journal of Aerospace System Engineering
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    • v.2 no.3
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    • pp.24-28
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    • 2008
  • Eddy current are induced when a nonmagnetic, conductive material is moving as the result of being subjected to the magnetic field, or if it is placed in a time-varying magnetic field. These currents circulate in the conductive material and are dissipated, causing a repulsive force between the magnet and conductor. Using this concept, eddy current damping can be used as a form of viscous damping. This paper investigated analytically and experimentally the characteristics of an eddy current damping when a permanent magnet is placed in a conductive tube. The theoretical model of the eddy current damping is developed from electromagnetics and is verified from Maxwell program and experiments. From these comparisons, although predictability is not accurate at high excitation frequencies, the present model can be used to predict damping force at low excitation frequencies. In order to improve the prediction of the characteristics of an eddy current damping, the induced magnetic flux densities have to be considered in following researches.

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Switched Reluctance Contact-Free Linear Actuator Using Attractive Magnetic Forces (자기 흡인력에 의한 비접촉식 SR 형 선형 구동기)

  • 이상헌;정광석;백윤수
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.10
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    • pp.47-55
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    • 2003
  • In the development of positioning device for precision manufacturing and measuring, the friction from mechanical contact causes serious decrease of performance. In this study, we studied about variable reluctance type contact-free linear actuator to overcome drawbacks from friction. In the view of electromagnetics, we analyzed and derived theoretical magnetic force equation and designed structure for generating suspension and propulsion force simultaneously. In the view of dynamics, we derived equation of motion and identified the stability of the system. Finally, we verified the feasibility of the proposed system.

Correlating Fully Anechoic Chamber to Open Area Test Site Measurements by the Normalized Site Attenuation

  • Kang, Tae-Weon;Kim, Byung-Wook;Chung, Yeon-Choon;Kim, Hyo-Tae
    • Journal of electromagnetic engineering and science
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    • v.1 no.2
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    • pp.126-130
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    • 2001
  • The performance of a fully anechoic chamber (FAC) for radiated emission (RE) measurements has been evaluated using the normalized site attenuation (NSA). To do this, the antenna factor (AF) of a set consisting of nearly identical antennas has been calibrated at an open area test site (OATS). Appropriate correlation factor (CF) between the chamber and the OATS has been calculated. Results show that the performance of the chamber is fairly good with respect to the ANSI-limit except 41~66 MHz far vertical polarization and near 900 MHz for horizontal polarization.

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A study for Decision Method of Human Body Safety according to Power Load Fluctuation of the Chechon Area (제천지역 전력부하변동에 따른 인체 전 판단 방법에 대한 연구)

  • 김상철;김두현
    • Journal of the Korean Society of Safety
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    • v.15 no.4
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    • pp.69-77
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    • 2000
  • This paper presents a study for decision method of human body safety according to power load fluctuation of the Chechon area. To cope with substantial electromagnetics analysis, the safety assessments were analyzed the double 154 [kV] T/L, 345 [kV] T/L, Chechon-Ichon, Chechon-Youngju, respectively. As the results of case study, in case of 345 [kV] T/L, the electric field value was 11.4927 [kV/m], magnetic field value was 0.4622 [G] at the point about 7 [m] away from the line in severest case. The results showed that the membership of a proposition fuzzy '11.4937 [kV/m] is hazardous' is 0.7063 for the severest case in case of 345 [kV] T/L. As the analytic results using the fuzzy qualifier term, the membership in case of very false is 0.0862 and fairly false is 0.5419, respectively.

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A Study on Optimization of Compact High-voltage Generator Based on Magnetic-core Tesla Transformer

  • Jeong, Young-Kyung;Youn, Dong-Gi;Lee, Moon-Qee
    • Journal of Electrical Engineering and Technology
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    • v.9 no.4
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    • pp.1349-1354
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    • 2014
  • This paper presents a compact and portable high-voltage generator based on magnetic-core Tesla transformer for driving an UWB high power electromagnetic source. In order to optimize the performance of the high-voltage generator, a novel open-loop cylindrical magnetic-core adopting the quad-division lamination structure is proposed and manufactured. The designed high-voltage generator using the proposed magnetic core has a battery-powered operation and compact size of $280mm{\times}150mm$ in length and diameter, respectively. The high-voltage generator can produce a voltage pulse waveform with peak amplitude of 450 kV, a rise time of 1.5 ns, and pulse duration of 2.5 ns at the 800 V input voltage.

Linear Motor Design by using Topology Optimization (위상최적설계를 이용한 리니어 모터의 설계)

  • Lee, Heon;Kang, Je-Nam;Wang, Se-Myung;Hong, Eon-Pyo;Park, Kyeong-Bae
    • Proceedings of the KIEE Conference
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    • 2003.07b
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    • pp.843-845
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    • 2003
  • In this paper, the design of the outer core which is one part of the linear motor is investigated by using the topology optimization and FEM. The object functions are to reduce the outer core area of the linear motor with the maximum magnetic energy in airgap. For topology optimization, the finite element model is made through the result of ANSYS, and the sensitivity calculation is done using ANSTOP(developed general software for topology optimization of electromagnetics). In ANSTOP, the optimization routine is implemented using SLP in DOT and the ANSYS is used as a function solver.

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An Experimental Study on the Electromagnets for the Electromagnetics Maglev Vehicle(III) (상전도 흡인식 자기부상열차용 전자석에 대한 실험적 연구(III))

  • Kim, Bong-Seop;Chung, Hyun-Kap
    • Proceedings of the KIEE Conference
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    • 1996.11a
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    • pp.12-14
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    • 1996
  • Static tests on the performance of the electromagnets of the electromagnetic maglev vehicle were conducted. Performance of the magnets wound with the alumimum sheet were tested and compared with that of the magnets constructed with aluminum coils of rectangular cross section. It turns out that with the use of the aluminum sheet we can improve the lifting force per magnet by 19.5% and thereby make electromagnets lighter than those made with the aluminum coils of rectangular cross section.

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A Damped Sinusoidal Electromagnetic Pulse Generator using a Charged Line (충전선로를 이용한 Damped Sinusoidal 전자기펄스 발생장치)

  • Ryu, Ji-Heon
    • Journal of the Korea Institute of Military Science and Technology
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    • v.9 no.2 s.25
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    • pp.136-142
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    • 2006
  • A damped sinusoidal electromagnetic pulse generator was designed, fabricated and tested. The pulse generator consisted of an oscillator(a spark gap switch and an initially charged low impedance line) and a high impedance antenna. This generator was capable of producing damped sinusoidal pulses at closure of the spark gap switch. A Marx generator was employed to supply the Pulse generator with high voltage pulses. While the pulse generator was provided with the high voltage pulses of 200kV from the Marx generator, its output power was maximized by controlling the pressure of the gas contained in the spark gap switch. The output power of the damped sinusoidal electromagnetic pulse oscillator was 1.3GW and the amplitude of electric field radiated from the pulse generator was 4kV/m at the range of 25m.

Sampling-Based Sensitivity Approach to Electromagnetic Designs Utilizing Surrogate Models Combined with a Local Window

  • Choi, Nak-Sun;Kim, Dong-Wook;Choi, K.K.;Kim, Dong-Hun
    • Journal of Magnetics
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    • v.18 no.1
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    • pp.74-79
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    • 2013
  • This paper proposes a sampling-based optimization method for electromagnetic design problems, where design sensitivities are obtained from the elaborate surrogate models based on the universal Kriging method and a local window concept. After inserting additional sequential samples to satisfy the certain convergence criterion, the elaborate surrogate model for each true performance function is generated within a relatively small area, called a hyper-cubic local window, with the center of a nominal design. From Jacobian matrices of the local models, the accurate design sensitivity values at the design point of interest are extracted, and so they make it possible to use deterministic search algorithms for fast search of an optimum in design space. The proposed method is applied to a mathematical problem and a loudspeaker design with constraint functions and is compared with the sensitivity-based optimization adopting the finite difference method.