• Journal of Magnetics
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• v.21 no.4
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• pp.516-523
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• 2016

In this paper, coupling factors are calculated based on numerical analysis in order to assess various non-uniform low-frequency magnetic field exposure situations. Two types of non-uniform magnetic field sources are considered; circular coil and parallel wires with balanced currents. For each magnetic field source, source current values are determined so that reference magnetic field magnitude can be measured at the specified point on the human model. Various exposure situations are investigated by changing parameters such as the distance between source and human model, radius of circular coil, and the gap between parallel wires. For equivalent human models, prolate spheroid model and simplified human model from IEC 62311 standard are used. The calculated coupling factor values are compared with those obtained by 2D uniform disk human model, and the dependence of coupling factor on the choice of equivalent human model is analyzed.

• Progress in Superconductivity
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• v.13 no.3
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• pp.151-157
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• 2012

In this paper, we used E-J constitutive law and H-formulation to calculate magnetic field profile, current density, and magnetization of high temperature superconductor (HTS) placed in time varying applied magnetic field. Finite element method (FEM)-based software, Comsol Multiphysics 3.5a, was employed to simulate 2-dimensional model of a superconducting thin strip. The numerical results based on Kim's critical state model were compared with the case of strip in a perpendicular field in the Brandt's paper as well as experimental data observed by Scanning Hall Probe and SQUID.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.29-34
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• 2013

AMR (Active Magnetic Regenerative) refrigerators require the large variation of the magnetic field and a HTS magnet can be used. The amount of AC loss is very important considering the overall efficiency of the AMR refrigerator. However, it is very hard to estimate the precise loss of the HTS magnet because the magnetic field distribution around the conductor itself depends on the coil configuration and the neighboring HTS wires interact each other through the distorted magnetic field by the screening current Therefore, the AC loss of HTS magnet should be calculated using the whole configuration of the HTS magnet with superconducting characteristic. This paper describes the AC loss of the HTS magnet by an appropriate FEM approach, which uses the non-linear characteristic of HTS conductor. The analysis model is based on the 2-D FEM model, called as 'magnetic field formulation and edge-element model', for whole coil configuration in cylindrical coordinates. The effects of transport current and stacked conductors on the AC loss are investigated considering the field-dependent critical current. The PDE model of 'Comsol multiphysics' is used for the FEM analysis with properly implemented equations for axisymmetric model.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.253-255
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• 2000

This paper describes the operating characteristic analysis of PM-type magnetic circuit breaker for electromagnetic field, electric circuit and mechanical motion problems. Transient calculations based up 2D finite element magnetic field solution including non-linearity of materials. Change of dynamic characteristic from eddy current in mover is quantified from FEM analysis.

• Wind and Structures
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• v.25 no.2
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• pp.131-156
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• 2017

This paper deals with the dynamic stability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced micro cylindrical shells. The structure is subjected to harmonic non-uniform temperature distribution and 2D magnetic field. The CNT reinforcement is either uniformly distributed or FG along the thickness direction where the effective properties of nano-composite structure are estimated through Mixture low. The viscoelastic properties of structure are captured based on the Kelvin-Voigt theory. The surrounding viscoelastic medium is considered nonhomogeneous with the spring, orthotropic shear and damper constants. The material properties of cylindrical shell and the viscoelastic medium constants are assumed temperature-dependent. The first order shear deformation theory (FSDT) or Mindlin theory in conjunction with Hamilton's principle is utilized for deriving the motion equations where the size effects are considered based on Eringen's nonlocal theory. Based on differential quadrature (DQ) and Bolotin methods, the dynamic instability region (DIR) of structure is obtained for different boundary conditions. The effects of different parameters such as volume percent and distribution type of CNTs, mode number, viscoelastic medium type, temperature, boundary conditions, magnetic field, nonlocal parameter and structural damping constant are shown on the DIR of system. Numerical results indicate that the FGX distribution of CNTs is better than other considered cases. In addition, considering structural damping of system reduces the resonance frequency.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.522-522
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• 1996

An investigation of the effects of transverse magnetic field and Peltier effect on melt convection and macrosegregation in vertical Bridgman crystal grosth of Te doped InSb was been carried out by means of microstructure observation, Hall measurement, electrical resistivity measurement and X-ray analysis. Before the experiments, Interface stability, convective instability and suppression of convection by magnetic field were calculated theoretically. After doping 1018, 1019 cm-3 Te in InSb, the temperature of Bridgman furnace was set up at $650^{\circ}C$. The samples were grown in I.D. 11mm, 100mm high quartz tube. The velocity of growth was about 2${\mu}{\textrm}{m}$/sec. In order to obtain the suppression of convection by magnetic field in the middle of growth, 2-4KG magnetic field was set on the melt. For searching of the shape of solid-liquid interface and the actual velocity of crystal growth, let 2A current flow from solid to liquid for 1second every 50seconds repeatedly (Peltier effect). The grown InSb was polycrystal, and each grain was very sharp. There was no much difference between the sample with and without magnetic field at a point of view of microstructure. For the sample with Peltier effect, the Peltier marks(striation) were observed regularly as expected. Through these marks, it was found that the solid-liquid interface was flat and the actual growth velocity was about 1-2${\mu}{\textrm}{m}$/sec. On the ground of theoretical calculation, there is thermosolutal convection in the Te doped InSb melt without magnetic field in this growth condition. and if there is more than 1KG magnetic field, the convection is suppressed. Through this experiments, the effective distribution coefficients, koff, were 0.35 in the case of no magnetic field, and 0.45 when the magnetic field is 2KG, 0.7 at 4KG. It was found that the more magnetic field was applied, the more convection was suppressed. But there was some difference between the theoretical calculation and the experiment, the cause of the difference was thought due to the use of some approximated values in theoretical calculation. In addition to these results, the sample with Peltier effect showed unexpected result about the Te distribution in InSb. It looked like no convection and no macrosegregation. It was thought that the unexpected behavior was due to Peltier mark. that is, when the strong current flew the growing sample, the mark was formed by catching Te. As a result of the phenomena, the more Te containing thin layer was made. The layer ruled the Hall measurement. The values of resistivity and mobility of these samples were just a little than those of other reference. It was thought that the reason of this result was that these samples were due to polycrystal, that is, grain boundaries had an influence on this result.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.4
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• pp.64-70
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• 1994

the magnetic field homogeneities of the induction coils of various sizes and shapes were investigated in order to prepare for the magnetic field immunity test under the power frequency, the pulse and the damed oscillatory fields recommended by the IEC. For this purpose, we analyzed the magnetic field homogeneities in the two induction coils with $1m\times1m$, and $1m\times2.6m$, , and the double square coils with 0.8m and 0.6m spaced. The testing volume within $\pm$3dB in the double square coil with 0.8m spaced in twice bigger than single square coil with 1m side in the z-direction.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.212-214
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• 2003

A passive loop is considered to be a cheap and easy way to be realized among the magnetic field mitigation methods. So this paper evaluates and quantizes systematically the effectiveness of a passive loop on mitigating magnetic field(M-field) and examines the feasibility and problems in adoption. To do so, first, we explain the principles of M-field mitigation through a passive loop and derive formulas for 2-D M-field analysis. Next this paper simulates the M-field mitigation patterns for a flat type 1-circuit transmission line installed a passive loop.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.22-24
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• 1997

The 4-pole LHSM was composed of the figure-of-eight shaped 3-phase armature windings. DC field windings, and the segmented secondary with the transverse bar track. The motor was designed on the base of the performance characteristic equations and the equivalent circuit model, with the coefficients of the magnetic shape. These coefficients were computed from the analytical expressions and examined from FEM analysis. The magnetic equivalent circuit of 3-D model of LHSM was obtained. and this concept provided the equivalent models for 2-D FEM analysis. Therefore, the airgap field, the lift and thrust force were calculated and compared with the results of magnetic equivalent circuit method.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.271-273
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• 2000

A magnetic field generator for small animal study was designed and constructed. For calculation of magnetic fields inside the cage, a three-dimensional calculation program was made. Using this, optimum electric current ratio and position of each coil were determined. Meanwhile, inductance of the generator was calculated for design of power supply. The field measurement results of the manufactured generator showed that the difference between maximum and minimum magnetic field at the living floor was less than 2%.