• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권5호
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• pp.245-249
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• 2006

This study tries to test and analyze the static friction torque generated by an electromagnetic clutch. Then the torque is improved by optimizing the shape of armature. For the purpose of design change and optimization of the electromagnetic clutch, the static friction torque prediction is very important. We construct an axi symmetric FEM model for analyzing the static friction torque and used a torque tester for evaluating the real torque. For a test, predicted static friction torque is compared with the experimental one to discuss the rationality of torque analysis process. The analytical result agrees well with experimental data, explaining the validity of the mathematical process and FEM model. After confirming the torque analysis process, the optimization process is investigated. The optimization result shows that the static torque is improved by changing the armature shape.

• Progress in Superconductivity
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• 제3권2호
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• pp.183-187
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• 2002

In this paper we analyzed the electromagnetic behavior of high $-T_{c}$ superconductor under the quench state using finite element method. Poisson equation was used in finite element analysis as a governing equation and was solved using algebra equation using Gallerkin method. We first investigate d the electromagnetic behavior of U-type superconductor. Finally we applied our analysis techniques to 5.5 kVA meander-line superconducting fault current limiters (SFCL) which are currently developed by many power-system researcher in the world. Meshes of 14,600 elements were used in analysis of this SFCL. Analysis results show that the distribution of current density was concentrated to inner curvature in meander-line type-superconductors and maximum current density 14.61 $A/\m^2$ and also maximum Joule heat was 6,420 W/㎥. We concluded that this meander line-type SFCL was not pertinet fur uniform electromagnetic field distribution.n.

• 한국기계가공학회지
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• 제17권5호
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• pp.131-136
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• 2018

Research on space development and satellites is being actively pursued. An interesting field is the study of reliable low-cost space launch vehicles. Since chemical fuel-based launching systems are expensive and take a lot of time and cost to maintain, the EML system, which is an electromagnetic force launching apparatus, is attracting attention. The EML system converts electrical energy stored in a capacitor into magnetic energy, and converts magnetic energy into mechanical kinetic energy, thereby accelerating the projectile. Although studies are actively conducted in the field, it is difficult to solve the equation because the impedance and speedance change with time and the nonlinearity is strong. Many researchers have solved this equation in a variety of methods. In this paper, the velocity analysis of the projectile was carried out by FEM (finite element method) using the commercial electromagnetic analysis program MAXWELL.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2049-2057
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• 2014

In this paper, a numerical method for analyzing coupling between high-altitude electromagnetic pulse (HEMP) as external field and a shielded twisted pair (STP) cable is proposed, which is based on an expanded chain matrix. Load responses of electromagnetic (EM) field excitation in uniform transmission line (TL) are solved by Baum-Liu-Tesche (BLT) equations in frequency domain, however, it is difficult to apply BLT equations to solve load responses of STP cable because the iteratively changing configuration of each twisted pairs are involved in cable. To avoid this problem and decrease memory and CPU time, we proposed the expanded chain matrix modeling method that is calculated using ABCD parameters, and applied multi-conductor transmission line (MTL) theory to consider the EMP coupling effectiveness of each twisted pairs. The results implemented by the proposed method are presented and compared with those obtained by the finite-difference time domain (FDTD) method as a kind of 3D full wave analysis.

• 한국실천공학교육학회논문지
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• 제2권2호
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• pp.55-60
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• 2010

평상시 전자기 현상들을 접하고 있는 우리들은 이러한 현상들의 단편적인 면은 느낄 수 있으나 시각적으로 파악하기 어려운 현상이며 더욱이 물리 및 정량적으로 이해하기란 쉬운 일이 아니다. 이들 정전기장, 정자기장 또한 전자장이 결합되어있는 교류자장은 실험식과 이론적으로 James Clerk Maxwell에 의해 1873년도에 완성되었다. 따라서 전자장은 Maxwell방정식에 근거를 둔 수식의 전개로 전기 자기 현상을 다룬다. 이러한 수식전개가 바탕이 되는 학문이기에 처음으로 전자기를 배우는 중 고등학교 학생, 대학 기본과목인 대학 물리를 배우는 대학생, 이와 관련된 전공 학생에게 조차 이해하기에 어려움이 따른다. 따라서 이러한 난점들을 해결하고자 전자기 제반현상들을 시각적으로 파악하고 더 나아가 수식적으로 해를 구하기 어려운 문제들을 수치해석방법을 이용해 해의 거동을 추정할 수 있도록 하는 학부 수준의 가상 교육용 전자장 프로그램을 개발하고자 하였다.

• Journal of Magnetics
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• 제7권2호
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• pp.45-50
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• 2002

A magnetic field annealing is firstly used for nanostructured Sm-Co/Co films, prepared by magnetron sputtering method. The effects of magnetic field annealing on single-layered Sm-Co films are different from those on multi-layered Sm-Co/Co films. A detailed analysis of microstructures and magnetic properties is made by means of HRTEM, Auger electron spectroscopy, XRD and Physical Property Measurement System (PPMS). From magnetic properties and microstructure analysis, it was confirmed that these differences originate from the effects of magnetic field annealing on crystallization behavior of the films. The relationship between magnetic properties and microstructures explains a different demagnetization process of single-layered and multilayered films. For the single-layered Sm-Co films, magnetic-field-annealing makes the main phases change from $CaCu_5/ to Zn_2Th_{17}$ structure, resulting in a decrease of coercivity. The results show that the magnetic-field-annealing is useful to improve the properties of nanostructured Sm-Co(30 nm)/Co(10 nm) films, which ascribe to improving the pinning effectiveness in coercivity mechanism and decreasing the magnetostatic interaction of films. A very high coercivity about 0.7 T was obtained from nanoscaled multi-layered Sm-Co(30 nm)-/Co(10 nm) films.

• Journal of electromagnetic engineering and science
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• 제4권1호
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• pp.13-16
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• 2004

In this paper, FDTD analysis of the bow-tie antenna is investigated by incorporating static field solution that is suitable to the bow-tie antenna without increasing computational time. Transforming static feld solution to the rotated grid system, we can obtain the transformed static field solution which is able to represent field behavior near the oblique edge line of the bow-tie antenna. The result shows a good agreement with a MoM analysis and is compared conformal modeling technique and regular FDTD method.

• 소성∙가공
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• 제16권2호
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• pp.113-119
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• 2007

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat material by means of an electric current that is caused to flow through the material or its container by electromagnetic induction. It has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers a finite element analysis of the induction heating process which can rapidly raise mold temperature. To simulate the induction heating process, the electromagnetic field analysis and transient heat transfer analysis are required collectively. In this study, a coupled analysis connecting electromagnetic analysis with heat transfer simulation is carried out. The estimated temperature changes are compared with experimental measurements for various heating conditions.

• 대한기계학회논문집A
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• 제30권12호
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• pp.1557-1563
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• 2006

A scanning electron microscope (SEM) is well known as a measurement and analysis equipment in nano technology, being widely used as a crucial one in measuring objects or analyzing chemical components. It is equipped with an electron optical system that consists of an electron beam source, electromagnetic lenses, and a detector. The present work concerns numerical analysis for the electron optical system so as to facilitate design of each component. Through the numerical analysis, we investigate trajectories of electron beams emitted from a nano-scale field emission tip, and compare the result with that of experimental observations. Effects of various components such as electromagnetic lenses and an aperture are also discussed.

• Journal of Magnetics
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• 제16권4호
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• pp.374-378
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• 2011

Axial Field Permanent Magnet (AFPM) generators are widely applied for the small wind turbine because of the higher power density per unit weight than that of the conventional radial field generator. It is caused by the disc shaped rotor and the stator structures. The generally used AFPM generator, AFER-NS generator, is composed of the two side's external rotors and non-slotted stator without stator core. However, the output voltage and the output power are limited by the large reluctance by the long air-gap flux paths. In this paper, the design study of AFIR-S generator having double side's slotted stator core is accomplished to improve the output generation characteristics. The electromagnetic design analysis and the design improvement of the suggested AFIR-S generator are studied. Firstly, the electromagnetic design analysis was done to increase the power density. Secondly, the design optimizations of the rotor pole-arc ratio of permanent magnet are accomplished to increase the output power and to reduce the cogging torque. Finally, the output performances of AFER-NS and AFIR-S generator are compared with each other. For this study, 3D FEA is applied for the design analysis because of three dimensional electromagnetic structures.