• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.961-963
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• 2003

Magnetization losses of HTS depend strongly on the orientation of external magnetic field because of anisotropy characteristics. For parallel and perpendicular magnetic field, analytical models to calculate the loss are well known but there is no analytical model for magetic fields which are applied to surface of HTS with arbitrary angle. In this paper, magnetization losses are measured for various incidence angles($15^{\circ}$, $35^{\circ}$, $45^{\circ}$, $60^{\circ}$) and compared with parallel and perpendicular loss. As a result, magnetization losses in HTS are strongly affected by perpenducular magnetic field component of external magnetic field.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.91-98
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• 2004

TFLIM(Transverse Flux Linear Induction Motor), making its closed magnetic path with the direction of the traveling field orthogonal, had been developed to decrease an edge effect of the general induction motor. To control the levitation force and the thrust force on the secondary part of TFLIM independently, the various methodologies have been presented. When we try to achieve the independent control using only the multi-phase inputs assigned in the stator coils as an approach, in which condition we can minimize the coupling effect between two forces\ulcorner In this paper, we show the qualitative influence of a slip frequency, an ac magnitude, a dc offset superposed in the ac power, and a major parameter of TFLIM on the couple through the computer simulation. And to realize the independent motions between levitation and thrust motion without any auxiliary means fur isolation of the secondary part of TFLIM, the decouple compensator is suggested, including the experimental results.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.102-103
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• 2001

In this paper we calculate the AC Loss in the superconducting slab carrying ac transport current. Magnetic diffusion equation for computation of the electric field and current distribution are based on Maxwell's equations and non-linear constitutive equation. The E-J characteristics of superconductor are applied to computation. We will present the result of the high-temperature superconductor case comparison with the slab of low temperature superconductor.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.139.2-139.2
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• 2015

In this study, We applied the magnetic field that has CW frequency and AM frequency to heating magnetic nano powder. For this experiment, We set up the devices flat-type magnetic field generator with CW frequency and AM frequency. We supplied the current to encircling coil by adjusting the power of generating of magnetic field device for AC voltage through Slidacs and using way of LC resonance circuit and SMPS(Switching Mode Power Supply). Above the encircling coil, We covered the circular flat insulator like glass. And we located the well plate containing the magnetic nano powder liquor above the circular flat insulator and exposed the magnetic field to this well plate. Using the flat-type magnetic field generator with CW and AM frequency and the magnetic field measurement sensor(Magnetic pick up coil or Hall sensor), We measured the strength of the magnetic field of circular flat insulator's surface in each position. The temperature of the magnetic nano powder in the well plate was quantitatively measured by the magnetic field strength through the Fluoroptic thermometer.

• Progress in Superconductivity and Cryogenics
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• v.1 no.1
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• pp.38-41
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• 1999

Strands composing multistage superconducting cables for AC power applications have twisted structure in each stage for lower AC loss and higher stability. So, when transport currents flow in a cable, each strand is exposed to longitudinal and azimuthal magnetic fields produced by transport current flowing in strand itself and Iongitudinal and transverse magnetic fields by transport current flowing in twisted cable. In this paper. we study the influence on self field lesses generated in second stage superconducting cable for different twist direction of filaments in a strand considering twist of strands in cables.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.99-101
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• 2001

Magnetization loss which is generated in HTS wire varies with the direction of the external magnetic field. This paper calculates the magnetization loss in an HTS transformer winding, where effects of the direction of magnetic field are considered. Kim model is used to consider the variation of the critical current with magnetic field and Brandt equation is used to calculate the loss by perpendicular magnetic field in transformer winding. Magnetization loss in an HTS transformer can be calculated more precisely with this paper.

• Progress in Superconductivity
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• v.7 no.1
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• pp.22-27
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• 2005

We have studied the standardization of critical temperature measurements by using an ac susceptometer. Wire forms of NbTi, $Nb_{3}Sn$, and Bi-2223 superconductors were prepared to measure the temperature dependences of the magnetization. In order to study the optimum ac magnetic field and frequency, various amplitudes from 2 Oe to 10 Oe with frequencies from 11.3 Hz to 1033 Hz were applied to three specimens. Analytical comparison of the magnetic curves with the resistive curves was accomplished to investigate validity of using the new method.

• Advances in nano research
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• v.1 no.3
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• pp.171-182
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• 2013

The alternating current (AC) conductivity in semiconductor crystals with an open-core screw dislocation is studied in the current work. The screw dislocation in crystalline media results in an effective potential field which affects the electronic transport properties of the system. Therefore, from a technological view point, it is interesting to investigate properties of AC conductivity at frequencies of a few terahertz. To quantify the screw-induced potential effect, we calculated the AC conductivity of dislocated crystals using the Kubo formula. The conductivity showed peaks within the terahertz frequency region, where the amplitude of the AC conductivity was large enough to be measured in experiments. The measurable conductivity peaks did not arise in dislocation-free crystals threaded by a magnetic flux tube. These results imply different conductivity mechanisms in crystals with a screw dislocation than those threaded by a magnetic flux tube, despite the apparent similarity in their electronic eigenstates.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.43-46
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• 2007

Solenoid coil is one of the commonly used one in superconducting power machines because it can produce uniform magnetic field at the center of the coil. Most of the AC loss in a solenoid coil is magnetization loss which is generated by the perpendicular magnetic field. This paper compares the electrical characteristics of two solenoid coils made of YBCO wire and BSCCO wire. We made and tested the BSCCO solenoid coil and YBCO solenoid coil which had the same number of turns and inner diameter. Number of turns and inner diameter of both coils were 30 turns and 10cm, respectively. AC loss of both coils were calculated by using the finite element method. Result shows that AC loss of YBCO coil was about 1/7 of that of the BSCCO coil when the current was 40A.

• Journal of Magnetics
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• v.17 no.1
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• pp.42-45
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• 2012

We have developed an alternating magnetic field stimulation system consisting of a switched-mode power supply and a digital control circuit which modulates a duty ratio to maintain a magnetic field intensity of a few mT even while the frequency increases up to 4 kHz with a controllable coil temperature below $30^{\circ}C$ in air. This duty ratio modulation and water circulation are advantageous for cell culture under ac-magnetic field stimulation by preventing the incubator from exceeding a cell-viable temperature of $37^{\circ}C$. Although the temperature of the coil when subjected to a sinusoidal voltage rapidly increased, that of our system modulated by the duty factor did not change. This is a potentially valuable method to investigate the effects of intermediate frequency magnetic field stimulation on biological entities such as cells, tissues and organs.