• Journal of Magnetics
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• v.13 no.4
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• pp.170-172
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• 2008

Fe-6.5% Si alloys have good magnetic properties due to their high electrical resistivity, very low magneto-striction, and low crystalline anisotropy. Despite their strong potential, these alloys have seldom been used in magnetic applications because of the very poor ductility of Si-steel above 3.0 wt% Si [1-4]. It is difficult to achieve compressed Fe-6.5% Si powder cores with excellent properties because of the low density due to poor ductility. In compressed powder cores, high density is essential in order to obtain high magnetization and permeability. In this study, an attempt was made to produce Fe-3%Si powder cores because the Fe-3.0 wt% Si alloys have relatively good magnetic properties and room temperature ductility. Gas atomized Fe-3.0 wt% Si powder was compressed into toroid shape cores. By reducing the Si content to 3.0 wt%, the hysteresis loss could be greatly reduced and thus the total core loss could be minimized. The total core loss is 600 mW/$cm^3$ at 0.1 T and 50 kHz.

• Journal of Magnetics
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• v.20 no.2
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• pp.138-147
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• 2015

The unique nano-scale inter-lamellar microstructure and unparalleled heat treatment process give our developed metal powder composite its outstanding magnetic property for power inductor & motor applications. Compared to the conventional polycrystalline Fe or amorphous Fe-Cr-Si-B alloys, our unique designed inter-lamellar microstructure strongly decreases the intra-particle eddy current loss at high frequencies by blocking the mutual eddy currents. The combination of optimum permeability, magnetic flux and extremely low core loss makes this powder composite suitable for high frequency applications well above 10 MHz. Moreover, it can be also possible to SMC core for high speed motor applications in order to increase the motor efficiency by decreasing the core loss.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.524-529
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• 2000

Silica slab wavegudie was fabricated on Si substrates by FHD for planar optical passive devices. The slab waveguide consists of lower clad and core layers, where core layer index is controlled by GeO2 addition. Doping of GeO2 in silica is difficult because of the low deposition density due to nonspherical particle generation in FHD process. Silica core particles deposited at various conditions such as flame temperature and substrate scanning were analyzed by SEM and TEM. As the flame temperature increased, the surface roughness of the core layer was decreased up to 3.6 nm after consolidation. Index difference and thickness of core of slab waveguide were 0.3%, 8$\mu\textrm{m}$ respectively. Measured optical loss at TE mode was <0.04 dB/cm at 1.3$\mu\textrm{m}$ and <0.06 dB/cm at 1.55$\mu\textrm{m}$.

• Journal of Powder Materials
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• v.24 no.2
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• pp.122-127
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• 2017

Fe-6.5 wt.% Si alloys are widely known to have excellent soft magnetic properties such as high magnetic flux density, low coercivity, and low core loss at high frequency. In this work, disc-shaped preforms are prepared by spark plasma sintering at 1223 K after inert gas atomization of Fe-6.5 wt.% Si powders. Fe-6.5 wt.% Si sheets are rolled by a powder hot-rolling process without cracking, and their microstructure and soft magnetic properties are investigated. The microstructure and magnetic properties (saturation magnetization and core loss) of the hot-rolled Fe-6.5 wt.% Si sheets are examined by scanning electron microscopy, electron backscatter diffraction, vibration sample magnetometry, and AC B-H analysis. The Fe-6.5 wt.% Si sheet rolled at a total reduction ratio of 80% exhibits good soft magnetic properties such as a saturation magnetization of 1.74 T and core loss ($W_{5/1000}$) of 30.7 W/kg. This result is caused by an increase in the electrical resistivity resulting from an increased particle boundary density and the oxide layers between the primary particle boundaries.

• Resources Recycling
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• v.12 no.6
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• pp.8-12
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• 2003

According to the recent trend to raise the horizontal scan frequency to increase the image refinement of the High Definition TV and High Resolution Display, material with low core loss is required for the ferrite core for deflection yoke, which is secured even in the high frequency range. liking notice of the influence on the fine structure of Mg-Zn ferrite by the chemical com position and process, low temperature sintering was proceeded. Cu was added to the low loss Mg-Zn system ferrite. After select-ing MgO, ZnO, $Fe_2$$O_3$, CuO, MgO was substituted for CuO while varying the composition ratio. Then the sample was sintered for 3 hours between $980～1350^{\circ}C$ Magnetic permeability, power consumption, shrinkage rate, core loss were measured. The start-ing temperature to test the shrinkage of the sample was nearby $900^{\circ}C$, it increased according to the substitution process of Cu, and the firing temperature was lowered about $-50～-75^{\circ}C$ alongside of the process.

• Journal of the Korean Magnetics Society
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• v.9 no.3
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• pp.149-153
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• 1999

Frequency and temperature dependence of magnetic loss has been investigated in Mn-Zn ferrites containing the sesistive temary compounds of $SiO_2-CaO-V_2O_5$. The Mn-Zn ferrite with the composition of $MnO:ZnO:Fe_2O_3=36:11:53$(by mol %) are prepared by self-propagating high-temperature synthesis. From the results of frequency dependence of core loss, it has been found that the hysteresis loss is dominant at low frequency and the eddy current loss becomes more dominant as the frequency increases. With the addition of resistive compound, the frequency dependence of core loss, it has been found that the hysteresis loss is dominant at low frequency and the eddy current loss becomes more dominant as the frequency increases. With the addition of resistive compound, the frequency region where the hysteresis loss is dominant becomes wide. The core-loss minimum occurs at about 4$0^{\circ}C$ in the specimens with the additive because of the reduction in eddy current loss.

• Journal of Magnetics
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• v.1 no.1
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• pp.24-30
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• 1996

The relationship between effective permeability and the remanence ratio of an Fe-based amorphous alloy (Metglas 2605S3A) is investigated over a wide frequency range, in an effort to understand magnetization behavior of the alloy. In the frequency range from 1 to 200 kHz, the permeability is maximum at the remanence ratio of 0.4-0.5 and, at frequencies over 500 kHz, the correlation with negative coefficients emerges indicating that the permeability decreases with the remanent ratio, except for the ribbon coated with an insulating layer of MgO which exhibits both high values of the effective permeability and remanence ratio. It is considered from the correlation results that the boundary at which the dominant magnetization mechanism changes from domain wall motion to spin rotation is near 500 kHz. The core loss is also investigated as a function of annealing time when the samples are annealed at a fixed temperature of $435^{\circ}C$. The core loss in most cases decreases with the annealing time, the degree of the loss may consist of the hysteresis loss and anomalous eddy current loss. The two loss components are considered to be of similar magnitudes at low frequencies while, at high frequencies, the dominant contribution to the total loss is the anomalous loss.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.27-30
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• 1991

With the recent development of high performance AC superconducting wire of very small ac loss and large current carrying capacity, the possibility of superconducting air core transformer is being studied. The air core transformer has merits of no iron loss, no insulation to the core and no harmonics. But the air core transformer has large exciting current and low magnetic coupling factor. To increase the coupling factor, the transformer of toroidal shape is proposed and designed. (10KVA, 110/220V) Compared with air core transformer of solenoidal shape, the performance is improved. The exciting current occupies about 22% of the rated current.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.453-458
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• 2014

A novel high birefringent polymer terahertz (THz) fiber with a suspended elliptical core is proposed in this paper. The introduction of an elliptical core can enhance asymmetry to realize high mode birefringence, and a large porous outer cladding effectively isolates the core-guided mode from interacting with the surrounding environment. A full-vector finite element method(FEM) is used to analyze the characteristics of the THz fiber. Simulation results show that the suspended elliptical fiber exhibits high mode birefringence on a level of $10^{-2}$ over a wide frequency range, and an extremely large mode birefringence(${\approx}0.06226$) is obtained when ellipticity is 0.2. Moreover, a suspended hollow elliptical core fiber is also discussed for the purpose of lower loss, however high mode birefringence and low relative absorption loss can not coexist in such a kind of fiber.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.652-655
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• 2001

Power transformers are increasingly becoming more significant in the advancement of electronic equipment. A high-performance, low-cost core material is necessary in order th come up with power transformers in the smallest and lightest scale possible and with low power requirements. In this study, we added V$_2$O$_{5}$ and CaCo$_3$to Mn-Zn ferrite to produce a high-performance low-cost core material. The compositions used were MnO : ZnO : Fe$_2$O$_3$= 37 : 11 : 52 mol%. The materials were sintered at 125$0^{\circ}C$ for three hours. Initial permeability was measured at 0.1MHz. At 200mT, power loss was measured by changing the temperature at 25KHz, 50KHz, 100KHz. When we added 0.lwt% and 0.1%wt% of V$_2$O$_{5}$와 CaCo$_3$, respectively we obtained 405 405KW/㎥ at 200mT, 100KHz, 6$0^{\circ}C$. We tan reduce eddy current loss as a primary loss of high frequency by adding a small amount of V$_2$O$_{5}$와 CaCo$_3$. This reduces power loss in the power transformersormers