• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2230-2235
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• 2011

The purpose of this paper is to provide the unbalanced magnetic force and vibration mode comparison between two large interior permanent magnet machines(IPM) with different pole-slot combination considering stator and rotor eccentricity. Due to the punching tolerance, the mixed eccentricity of air-gap is inevitable. It will generate the asymmetric magnetic flux density in air-gap, which makes the unbalanced magnetic pull and vibration. The study is focused on the unbalanced magnetic force and their harmonic components according to eccentricity conditions such as static, dynamic and mixed. When the high vibration is produced especially resonance, the obtained results provide clues what eccentricity condition occurs in the machine.

• Polymer(Korea)
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• v.26 no.1
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• pp.98-104
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• 2002

This study was investigated to fabricate the isotropic $Nd_2Fe_{14}B$/epoxy bonded magnets with high characteristics paroduced by compression molding. The magnetic characteristics of the bonded magnets were directly proportional to the density of the magnets and were enhanced by using raw $Nd_2Fe_{14}B$ magnetic powders, having the mean particle size of $200{\mu} m$.without additional milling process. The high characteristics of the bonded magnets were achieved at the following conditions: epoxy resin of 2.0 wt%, silane coupling agent of 0.8 wt%, curing agent of 0.7 wt% on the base of magnetic powders, and curing condition of $150^{\circ}C$/3 hrs. The bonded magnets at the optimum conditions indicated the high characteristics such as the density of 6.1 g/㎤, the remanent flux density of 7.1 kG, the maximum energy product of 9.7 MGOe, and the compressive strength of 17 kg/$mm^2$.

• Applied Microscopy
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• v.47 no.1
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• pp.29-35
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• 2017

Transverse magnetic field annealing (TFA) was carried out on $Fe_{73.5}Cu_1Nb_3Si_{15.5}B_7$ nano-crystalline magnetic core with the aim at decreasing coercivity ($H_c$) while keeping high inductance ($L_s$). The magnetic field generated by direct current (DC) was applied on the magnetic core during different selected annealing stages and it was proved that the nanocrystalline magnetic core achieved lowest $H_c$ when applying transverse field during the whole annealing process (TFA1). Although the microstructure and crystallization degree of the nanocrystalline magnetic core exhibited no obvious difference after TFA1 compared to no field annealing, the TFA1 sample showed a more uniform nanostructure with a smaller mean square deviation of grain size distribution. $H_c$ of the nanocrystalline magnetic core annealed under TFA1 decreased along with the increasing magnetic field. As a result, the certain size nanocrystalline magnetic core with low $H_c$ of 0.6 A/m, low core loss (W at 20 kHz) of 1.6 W/kg under flux density of 0.2 T and high $L_s$ of $13.8{\mu}H$ were obtained after TFA1 with the DC intensity of 140 A. The combination of high $L_s$ with excellent magnetic properties promised this nanocrystalline alloy an outstanding economical application in high frequency transformers.

• Journal of the Korean Magnetics Society
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• v.20 no.3
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• pp.94-99
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• 2010

Minor B-H loop measurement for a rectangular high tensile steel was obtained by using Labview. A ferrite cores of high permeance with primary and secondary windings on the steel plate were used to form a closed loop of magnetic flux. To compensate errors due to an extremely small gap between a pair of ferrite core, and between the ferrite core and the rectangular high tensile steel, quadratic function of least square method was used. Also a 3D FEM magnetic analysis tool was used to measure H and B of the steel. B-H loop of the high tensile steel plate can be measured up to 520 A/m of a magnetic field and 0.15 T of a magnetic flux density.

• Tribology and Lubricants
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• v.13 no.2
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• pp.52-59
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• 1997

An experimental study is presented for the characteristics of the high temperature superconductor as an application of the repulsive type magnetic bearing. A ring shaped YBCO type superconductor and Neodium permanent magnets are employed for the experiment. For the case of field cooling, superconductor shows strong repulsive force, which is due to the Meissner effect, as the gap between the superconductor and the magnet gets closer. The repulsive force variation with respect to the gap change shows hysterisis characteristics. The area of the loop of the hysterisis curve represents the dissipation of energy, which reveals that the magnetic bearing with superconductor has large damping. The effect of the initial gap and the magnetic flux density on the repulsive force is analyzed experimentally and the static stiffness variation is calculated from the measured repulsive force variation. The relative sliding velocity between the superconductor and the magnet has little effect on the repulsive force which is quite different from the usual sliding element bearing. As the initial gap for the field cooling becomes larger, the maximum repulsive force at the minimum gap increases and approaches to the value for the case of zero field cooling.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.334-339
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• 1996

In order to investigate the influence of the magnetic paticle size and its properties on the particulate magnetic material, we evaluated the dispersion of magnetic particles and the electromagnetic properties in magnetic tape made from the magnetic paints by use of each magnetic particles witch were different from particle size and its propertis. The dispersion of magnetic particles depends on the surface chemical properties rather than particle size. As particle size is smaller, the packing ratio of magnetic particle and the magnetic flux density in tape increase. The output levels in playing back of tape incerase in wide frequency range from 315 Hz to 10 kHz and the noises decrease. It is very important to choose the size, the shape, the surface chemical properties and the magnetic properties of the magnetic particle in producing the high quality magnetic tape.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.787-794
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• 1995

To improvement the magnetic and frequency properties of YIG(Yttrium-Iron Garnet) in microwave region, it is investigated that the effect of $Al^{3+}$ ions on magnetic and frequency characteristics of YIG, using samples of basic YIG composition( $Y_{3}$F $e_{5}$ $O_{l2}$) added with A1$_{2}$ $O_{3}$ from 0 to 2.5 [mol%]. The measurment is conducted mainly for the structural properties and magnetical properties. The structural properties is measured using SEM(Scanning Electro Microscope), EDX(Energy-dispersive X-ray spectrometer) and XRD(X-ray diffraction equipment). The magnetical properties is measured with B-H curve tracer and impedance analyzer. As a result, it is confin-ned that the effect of eddy current loss is minimized while maintaining high saturation flux density of YIG, when YIG is added with 0.5 [mol%] of A1$_{2}$ $O_{3}$.>.>.

• Proceedings of the KIEE Conference
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• summer
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• pp.1052-1054
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• 2004

This paper deals with a Double type Transverse Flux Linear Motor(TFLM) which can be applied to high power system. This type can reduce overall system volume because of the configuration which has double flux path of prototype per phase, and less number of phase and turns. This TFLM is based on permanent magnet excitation, and the pole shape is designed to reduce attraction force between stator and mover poles. In the paper, the basic configuration of double type and the principle of movement are introduced. After performing the characteristic analysis by 3-dimensional equivalent magnetic circuit network, the results are discussed.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.157-162
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• 2015

Large scale superconducting magnetic energy storage (SMES) system requires very high magnetic energy density in its superconducting coils to enhance the energy capacity and efficiency of the system. The recent high temperature superconducting (HTS) conductors, so called 2G conductors, show very good performance under very high magnetic field so that they seem to be perfect materials for the large scale SMES coils. A general shape of the coil system with the 2G HTS conductor has been a tor oid, because the magnetic field applied perpendicularly to the surface of the 2G HTS conductor could be minimized in this shape of coil. However, a toroid coil requires a 3-dimensional computation to acquire the characteristics of its critical current density - magnetic field relations which needs very complicated numerical calculation, very high computer specification, and long calculation time. In this paper, we suggested an analytic and statistical calculation method to acquire the maximum magnetic flux density applied perpendicularly to the surface of the 2G HTS conductor and the stored energy in the toroid coil system. Although the result with this method includes some errors but we could reduce these errors within 5 percent to get a reasonable estimation of the important parameters for design process of the HTS toroid coil system. As a result, the calculation time by the suggested method could be reduced to 0.1 percent of that by the 3-dimensional numerical calculation.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.501-501
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• 2012

A 2.45 GHz electron cyclotron resonance (ECR) plasma source with a belt magnet assembly configuration (BMC) was developed for hyperthermal neutral beam (HNB) generation. A plasma source for high flux HNB generation should be satisfied with the requirements: low pressure operation, high density, and thin plasma. The ECR plasma source with BMC achieved high density at low operation pressure due to electron confinement enhancement caused by high mirror ratio and drifts in toroidal direction. The 2.45 GHz microwave launcher had a circularly bended WR340 waveguide with slits. The microwave E-field profile induced by the microwave launcher was studied in this paper. The E-field profile was a cups field perpendicular to B-filed at ECR zone. The optimized E-field profile and B-field were found for effective ECR heating.