• Journal of Magnetics
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• 제21권4호
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• pp.660-665
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• 2016

The electromagnetic apparatus plays an important role in high power electrical systems. It is of great importance to provide an effective approach for the optimization of the high power electromagnetic apparatus. However, premature convergence and few Pareto solution set of the optimization for electromagnetic apparatus always happen. This paper proposed a modified multi-objective particle swarm optimization algorithm based on the niche sorting strategy. Applying to the modified algorithm, this paper guarantee the better Pareto optimal front with an enhanced distribution. Aiming at shortcomings in the closing bounce and slow breaking velocity of electromagnetic apparatus, the multi-objective optimization model was established on the basis of the traditional optimization. Besides, by means of the improved multi-objective particle swarm optimization algorithm, this paper processed the model and obtained a series of optimized parameters (decision variables). Compared with other different classical algorithms, the modified algorithm has a satisfactory performance in the multi-objective optimization problems in the electromagnetic apparatus.

• 소성∙가공
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• 제19권1호
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• pp.38-43
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• 2010

Electromagnetic forming (EMF) method is one of high-velocity forming processes, which uses electromagnetic Lorentz force. Advantages of this forming technique are summarized as improvement of formability, reduction in wrinkling, non-contact forming and applications of various forming process. In this study, the EMF apparatus is developed. It is designed to be stored in 10 capacitors connected in parallel, each with a capacitance of $50{\mu}F$ and maximum working voltage of 5kV. The system has capacitance of $500{\mu}F$ and maximum stored energy of 6.25kJ. And EMF experiments are carried out to verify the feasibility of the EMF apparatus, which has enough forming force from the results of EMF experiment. In addition, peak current carrying a forming coil is predicted from theoretical background, and verified the predicted value compared with experimental value using the current measurement equipment. Consequently, EMF apparatus developed in this study can be applied to various EMF researches for commercialization.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제4B권4호
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• pp.180-183
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• 2004

This paper presents a description of the point collocation method and its application to the electromagnetic field computation. The interpolation scheme is based on the fast moving least square reproducing kernel approximation. In the method, the integration cell is not required and the essential boundary conditions can be enforced directly. Numerical simulations on 1-D and 2-D problems are carried out to validate the method. It is found that computational efficiency is higher than the general mesh-free methods.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권12호
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• pp.562-570
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• 2002

The Purpose of this paper is to design and manufacture an educational system in order to demonstrate the causes and effects of electromagnetic induction.'rho educational system described in this study is a "jumping ring apparatus". This system demonstrates the principle of electromagnetic induction, a force from AC sources, Lenz's law of repulsion and transformer. The educational system is composed of a jumping ring apparatus, a sensor array, encoder, A/D converter, D/A converter and nonlinear controller. The educational system is controlled by 586 PC using Turbo C program. The sensor array is composed of 20 optical sensors. The nonlinear controller consists of nonlinear control algorithm and control board included SCR, FET and phase controller. The A/D converter is used to show the height of ring position to analog for an education purpose. The control signal calculated from the nonlinear control of algorithm send control board through 8 bit D/A convertor. Experiment results are given to verify that Proposed nonlinear controller is useful in on line control of the educational system.al system.

• 소성∙가공
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• 제21권7호
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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.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.114-120
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• 2014

In this paper, a method for multi-physics analysis of the temperature-dependent properties of an oil-immersed transformer is discussed. To couple thermal fields with electromagnetic and fluid fields, an algorithm employing a user defined function (UDF) is proposed. Using electromagnetic analysis, electric power loss dependent on temperature rise is calculated; these are used as input data for multi-physics analysis in order to predict the temperature rise. A heat transfer coefficient is applied only at the outermost boundary between transformer and the atmosphere in order to reduce the analysis region. To verify the validity of the proposed method, the predicted temperature rises in high-voltage (HV) and low-voltage (LV) windings and radiators were compared with the experimental values.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.59-61
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• 2003

The natural element method is a kind of meshless Galerkin method. The shape function is derived from the natural neighbor coordinates interpolation scheme. Natural neighbor shape functions are $C^0$ everywhere, except the nodes where they are $C^0$. The numerical integration is carried out using the Delaunay triangles as the background cells. The method is applied to the test problems and simulation results show that the natural element method can give accurate solutions for the electromagnetic field problems.

• 한국전자파학회논문지
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• 제16권8호
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• pp.810-814
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• 2005

TEM 셀 내에 있는 혈액에 대한 삽입 손실과 반사율을 측정하여, 원하는 혈액 흡수 SAR(Specific Absorption Rate) 선택에 따른 TEM셀 입력 전력을 구하였다. 혈액 세포는 피부 세포와 함께 전자파 영향을 연구하기 위한 기준 세포이다. 따라서 SAR에 따른 혈액 세포에 인가할 전력 산출은 정확해야 함은 물론 타당성이 있어야 한다. 이 연구에서는 g당 혈액 세포가 받는 전력을 산출하기 위해 50 g의 혈액을 이용하여 전달 전력 감소를 측정하였다. 측정된 데이터로부터 휴대폰 전자파 생체 흡수율 SAR 0.8, 1.6, 3, 4 mW/g에 해당하는 TEM셀 입력 전력을 계산하였다. 이 연구 결과는 배양 세포의 전자파 방사 장치에 응용함을 목적으로 하고 있다.

• Journal of electromagnetic engineering and science
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• 제13권3호
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• pp.192-194
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• 2013

This paper proposes a validation model using a reverberation chamber for verification of the effectiveness and accuracy of the statistical power balance (PWB) method. The PWB method treats electromagnetic (EM) field distributions in certain environments as a representative value of an "ensemble" average, so a reverberation chamber is utilized as a testing apparatus to experimentally simulate the sets of measurement field "ensemble" inside a complex environment. Measurements are performed with various test conditions for environmental loss using flat absorbers, and front and side doors of the chamber. Comparison between the PWB analysis and the measurement results shows good agreement, indicating the usefulness of this statistical analysis method for stating the electromagnetic field inside the EM zone as a representative value to general structures.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.991-993
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• 1999

The method of measurement for contactless eddy-current conductivity using magnetic dipole field theory was suggested by M.C Chen[1], which calculate the eddy-current caused by exciting coil with Faraday's induction law. In this work, we have developed the apparatus for contactless measurement of conductivity or resistivity with the dipole field theory. The resistivity can be measured from several to a dozen $m{\Omega}{\cdot}cm$ range within maximum 30% error. At the high resistivity range above $100{\Omega}{\cdot}cm$, the standard deviation of measurement was very large as the induced voltage of sensing coil is small so it was difficult to measure the value precisely.