• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.370-376
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• 2009

The influence of magnetic saturation on electromagnetic field distribution in both a permanent-magnet direct-current (PMDC) motor and a field-winding (wound-field) direct-current (FWDC) motor, with the same output mechanical power, has been studied. In this paper, an approximate analytical method and time-stepping Finite Element Method (FEM) are used for prediction of Back-EMF and electromagnetic torque. No-load and rotor-lucked conditions, according to experimental measurements, and the FEM and analytical method studies of the motors have been considered. A sensitivity analysis has also been successfully accomplished on the major design parameters that affect motor performance. At last, these two DC motors are compared, in spite of their differences, on the basis of measured output characteristics.

• Journal of Power Electronics
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• v.9 no.1
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• pp.68-73
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• 2009

Automotive inverters may require current sensors for motor torque control, especially, in applications of hybrid electric vehicles or fuel cell vehicles. In this paper, to achieve a compact, integrated and low cost current sensor, a hall current sensor without magnetic core is introduced for integrating an automotive inverter. The compactness of the current sensor is possible by using integrated magnetic concentrators based on the Hall effect. Magnetic fields caused by three-phase currents are analyzed and a magnetic shield design is proposed for decoupling the cross-coupled field. It offers galvanic isolation, wide bandwidth (>100kHz), and accuracy(< 1%). Using 2D FEM analysis, its performance is demonstrated with design parameters at a U-shaped magnetic shield. The proposed coreless current sensor is tested with rated current to validate the linearity and accuracy.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1197-1198
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• 2008

There have been few papers using finite element method(FEM) to analyze arc driving force for spiral type vacuum interrupter electrode up to date while there have been many papers dealing with AMF type electrode by means of FEM. AMF analysis is very important in AMF type electrode because it has proportional relation with effective area which means the area of magnetic flux density above critical magnetic flux density to diffuse arc. In the same manner, arc driving force is an important factor to drive arc by Lorentz force. In this paper two models were calculated and compared by using commercial FEM software Maxwell 3D.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.314-319
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• 2008

In this paper, the electric field distribution induced inside the brain during Transcranial Magnetic Stimulation(TMS) has been thoroughly investigated in terms of tissue heterogeneity and anisotropy as well as different head models. To achieve this, first, an elaborate head model consisting of seven major parts of the head has been built based on the Magnetic Resonance(MR) image data. Then the Finite Element Method(FEM) has been used to evaluate the electric field distribution under different head models or three different conductivity conditions when the head model has been exposed to a time varying magnetic field achieved by utilizing the Figure-Of-Eight(FOE) stimulation coil. The results show that the magnitude as well as the distribution of the induced field is significantly affected by the degree of geometrical asymmetry of head models and conductivity conditions with respect to the center of the FOE coil.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.47-51
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• 2010

We already obtained magnetic behavior of superconducting Nb foil of linear type magnetic flux pump (LTMFP) by means of the FEM analysis. As well as, fundamental equations of pumping current were theoretically derived based on the pumping sequences according to the position of normal spot of the moving flux. In this paper, we experimentally investigated pumping performances of LTMFP with a wide range of traveling speed of magnetic field. In order to confirm the numerical and theoretical approaches, we explained the pumping characteristics of LTMFP by use of the calculation sequence of pumping current.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.10
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• pp.509-516
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• 2001

Isolated phase bus(IPS) has a special structure for carrying large current generated by a generator to a main transformer. In the analysis of IPB, the understanding of the magnetic field distribution generated by large current is important. Especially, while the bus conductor current is flowing, almost same amount of current as bus conductor current is induced in the enclosures under the influence of time varying magnetic field, and therefore the large electric loss and the deterioration of insulating capability might occur due to Joule heating effect. Hence for the optimal design of IPB satisfying the condition to minimize the loss, the accurate analysis of magnetic field distribution and the eddy current characteristics of three phase isolated phase bus have been investigated. In the analysis of time varying magnetic field, instead of finite difference method(FDM) which is generally used, finite element method with phasor concept is investigated under the assumption that the bus current is purely sinusoidal. The characteristics is studied along the phase angle by comparing the effect of eddy current on the magnetic field distribution with the case that eddy current is not considered, and also the effect of material, thickness and radius of enclosure on the eddy current distribution is discussed.

• 전자공학회논문지 IE
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• v.48 no.1
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• pp.1-6
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• 2011

In this study, it carried out Electromagnetic Field Analysis of Magnetic Bearing due to stator structure and it got the electrical characteristics of 3 structure types of AMB(Active magnetic bearing) systems to get optimal design criteria. The results of simulation in three types of AMB, using FEM method, type 1, 2, and 3 had many paths to move magnetic flux vectors from N pole to S pole and magnetic flux lines are transferred to rotor as a shaft. The paths help to rotate the rotors. So, their data of electrical properties carry out design of magnetic bearing system and the data help to make design criteria.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.1
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• pp.5-14
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• 2002

In this paper, we analyze inductive interference in conductive material around 345 kV power transmission line, and evaluate the effects of mitigation wires. Finite element method (FEM) is used to numerically compute induced eddy currents as well as magnetic fields around powder transmission lines. In the analysis model, geometries and electrical properties of various elements such as power transmission line, buried pipe lines, overhead ground wire, and conducting earth are taken into accounts. The calculation shows that mitigation wire reduces fairly good amount of eddy currents in buried pipe line. To find the optimum magnetic field shielding location of mitigation wire, we applied evolution strategy algorithm, a kind of stochastic approach, to the analysis model. Finally, it was shown that we can find more effective shielding effects with optimum location of one mitigation wire than with arbitrary location of multi-mitigation wires around the buried pipe lines.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1109-1112
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• 2015

A milatary ship without degaussing coil has a vertical magnetization to compensate magnetization induced by the vertical magnetic field component of earth magnetic field during demagnetization process. Flash D is very useful to acquire vertical magnetization. However this is hard to predict vertical magnetization. This experiment was investicated on another method, which used the only vertical bias magentic field. The specimens were prepared by thin Zn coated steel sheet with a thickness of 0.15mm. The shapes of 3 specimes was rectangular, triangular and circular cylinders. These shapes were corresponded to the shapes of bow, mid and stern of a vessel. Through FEM analysis, the difference of magnetic signatures for these specimens was recognized and the residual magnetization curve was measured. magnetic field was generated by a solenoid coil and magnetic signature was measured by a magnetic field sensor. A linearity between a vertical bias magnetic field and a vertical manetzation existed and the vertical magnetization of a miltary vessel was predicted by the linearity.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.767-769
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• 2017

Four-shell open-typed shield case was analyzed using 3D FEM. Analysis Dimension was $2m{\times}2m{\times}2m$. Length of shield case was 0.6m and its diameter was 0.1m, 0.08., 0.06m and 0.04m. Thickness and permeablility of shield case was all 1mm and 50,000. The excited magneic fields were earth magneic fields, which were 24A/m in the holizontal direction and 36A/m in the vertical direction, respectively. During FEM analysis, shield case was located at the direction of holizontal magnetic field and was rotated $90^{\circ}$. Magnetic field was $4.45{\times}10^{-2}A/m$ at the direction of holizontal magnetic field and $6.66{\times}10^{-4}A/m$ at the $90^{\circ}$ rotated direction.