• Proceedings of the KIEE Conference
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• summer
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• pp.878-880
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• 2004

In this paper, a new design of permanent magnetic actuator (PMA) for vacuum circuit breaker (VCB) with one coil is proposed. Electromagnetic characteristic analysis is performed numerically using finite element method (FEM) considering the nonlinearity of magnetic core and permanent magnet. The characteristics of proposed PMA with one coil is similar with that of the conventional PMA with two coils. The proposed PMA can simplify the control circuit because of the usage of one coil. Therefore, the reliability of VCB can be improved with the proposed model.

• Journal of Power Electronics
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• v.10 no.2
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• pp.176-180
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• 2010

This paper deals with a control method to reduce the torque ripple of a permanent magnet synchronous motor (PMSM) for electric power steering (EPS) systems. Such an application requires a very low torque ripple in order to maintain a good steering feel. However, because of spatial limitations, it cannot help having a partial saturation in the iron core of the PMSM for an EPS system, and this saturation results in a significant torque ripple. Thus, this paper analyzes the torque ripple caused by the magnetic saturation of a PMSM and proposes a method with respect to inductance measurement to verify the partial saturation. In addition, it is shown that a compensation current is needed in order to minimize the torque ripple when a PMSM is driven in the high torque region. The estimation process of the current and the torque ripple decreased by the current are presented and verified with test results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.05a
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• pp.120-122
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• 1994

We examined the magnetic properties as a function of annealing temperature of the as-quenched $Fe_{87}Zr_{7}B_{5}Ag_{1}$ amorphous alloy. The values of $H_{c}$=30m0e, $B_{a}$=0.44T and ${\mu}$i=146000 at $300^{\circ}C$ annealing treatment are obtained. The excel lent soft magnetic properties seem to result from the annihilation of quenching-Induced internal stress by the heat treatment and the change of microstructure due to the different relaxation behavior owing to adding insoluble element such as Ag. Therefore, the $Fe_{87}Zr_{7}B_{5}Ag_{1}$ amorphous alloy is quite promising for practical use as a core material in various transformers of high transformers of high frequency.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.323-327
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• 2017

Soft magnetic composite (SMC) material has recently received a significant attention in the area of high-speed machines because of its unique properties such as good design flexibility and low eddy current loss. However, SMC's electromagnetic property is poor compared to silicon steel in terms of saturation, relative permeability, and hysteresis loss. This paper presents a technique for utilization of SMC in two strategic designs of a switched reluctance machine (SRM) depending on a loss pattern. To investigate the effect of SMC's merits and demerits, the stator material is changed from laminated steel to SMC.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.131-133
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• 2001

2D analysis is impossible for Hybrid stepping motor(HSM) and 3D analysis is necessary because the permanent magnet is magnetized to the axial direction. In this paper, the characteristics of HSM are analyzed by using 3D equivalent magnetic circuit network method(3D EMCNM). In addition, the trapezoidal element is introduced for the exact permeance calculation in the complex shape machinery such as HSM. The magnetic saturation of core is considered.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.610-613
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• 1995

The effect of processing parameters such as milling, additives and sintering atmoshpere on the magnetic properties of Mn-Zn ferrite was investigated. The experiment was followed by general ceramic fabrication process and added additives were $CaCO_{3}$, $SiO_{2}$, $V_{2}O_{5}$, $ZrO_{2}$, and $Nb_{2}O_{5}$. The effects of additives could be divided into three categories which were formation ofliquid phase, substitution in lattice and inducing stress. Core loss smong the magnetic properties was dependent mainly on the additives and also correlated with processing parameters. As a result, an optimum condition of preparing process for a high quality Mn-Zn ferrite was suggested by controlling the correlation of each processing parameters.

• Journal of Magnetics
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• v.18 no.3
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• pp.260-267
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• 2013

In this paper a general 2-D model of a large air-gap synchronous machine either with non-magnetic or magnetic core rotor is investigated and electrical characteristics of the machine are analytically calculated. Considering the general model, analytical equations for magnetic field density in different regions of the large air-gap machine are calculated. In addition, self and mutual inductances in the proposed model of the machine have been developed, which are the most important parameters in the electromagnetic design and transient analysis of synchronous machines. Finite element simulation has also been performed to verify the obtained results from the equations. Analytical results show good agreement with FEM results.

• Progress in Superconductivity and Cryogenics
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• v.24 no.1
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• pp.1-7
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• 2022

So far, large-scale scientific devices such as nuclear fusion tokamaks and high energy circular accelerators were constructed using high-current conductors made of metallic superconducting wires. Recently, as REBCO superconducting wires usable in high magnetic fields have been developed by several companies, researchesto apply high current cable type REBCO conductors to next-generation large superconducting magnets were also started. High critical currents of several kA or more in high magnetic fields have been successfully demonstrated on test samples of REBCO cable conductors by several research groups. In this review article, the main features and properties of the representative high current REBCO conductors such as CORC(Conductor On Round Core), TSTC(Twisted Stacked-Tape Cable) and RACC(Roebel-Assembled Coated Conductor), which are currently being developed at abroad are briefly introduced. Research activities of high-current density REBCO MHOS(Multi HTS layers on One Substrate) conductor at KERI, whose structure is different from other cable type REBCO conductors are also shortly introduced.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.42.1-42.1
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• 2020

Filamentary structures pervade the whole kind of molecular clouds from low- to high-mass star-forming clouds, and the non-star-forming clouds. It is supposed to be a prerequisite stage of star formation, and hence how filaments and dense cores form is one of the critical questions in the early star formation study. We investigated the dynamics and chemistry of dense cores in IC5146 using TRAO FUNS (TRAO Survey of the nearby Filamentary molecular clouds, the Universal Nursery of Stars) data. In addition, we performed polarization observation using JCMT Pol-2 polarimetry to investigate the magnetic field morphology within a core-scale. In the presentation, we will present the result of TRAO FUNS and JCMT/Pol2 observation toward the filaments and dense cores in the IC5146. We aim to reveal the roles of gravity, turbulence, and magnetic field in the formation of dense cores in the western hub-filament structure of IC5146.

• Journal of Magnetics
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• v.20 no.3
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• pp.211-214
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• 2015

$Cr_2O_3$ nanoparticles were prepared via one-step reactive laser ablation of Cr in oxygen. The metastable $CrO_2$ phase was obtained through the subsequent oxidation of $Cr_2O_3$ nanoparticles under $O_2$ with gas pressures of up to 40 MPa. The as-prepared $Cr_2O_3$ nanoparticles are spherical or rectangular in shape with sizes ranging from 20 nm to 50 nm. High oxygen pressure annealing is effective in producing meta-stable $CrO_2$ from as-dried $Cr_2O_3$ nanoparticles, and the $Cr_2O_3$ nanoparticles exhibit a weak ferromagnetic behavior with an exchange bias of up to 11 mT that can be ascribed to the interfacial exchange coupling between uncompensated surface spins and the antiferromagnetic core. The $Cr_2O_3/CrO_2$ nanoparticles exhibit an enhanced saturation magnetization and a reduced exchange bias with an increasing faction of $CrO_2$ due to the elimination of uncompensated surface spins over the $Cr_2O_3$ nanoparticles when exposed to a high pressure of $O_2$ and/or possible phase segregation that results in a smaller grain size for both $Cr_2O_3$ and $CrO_2$.