• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.4
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• pp.158-163
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• 2001

Magnetization losses of a Bi-2223 tape in magnetic fields parallel to the tape surface were measured by a room temperature cancellation and a cryogenic temperature cancellation. The results indicate that the same loss data are observed for both methods. The magnetization losses are hysteretic because the measured losses agree well with calculated ones based on a critical state model. In the full field penetration cases the magnetization losses increase with the frequency but in the partial field penetration cases the influence of the frequency is opposite.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2001.02a
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• pp.185-188
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• 2001

Magnetization loss of a Bi-2223 tape in magnetic fields parallel to the tape surface was measured by a magnetization method. The results indicate that the magnetization loss is hysteretic because the measured loss agrees well with calculated one from a critical state model. In the full field penetration case the magnetization loss increases with the frequency but in the partial field penetration case the influence of the frequency is opposite.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.5
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• pp.496-500
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• 1991

The effects of annealing with and without magnetic field on magnetic properties of amorphous Fe-B-Si cores have been investigated as a function of toroidal stress. By decreasing the toroidal stress, the magnetic properties of the amorphous ribbon have beenimproved. Near 180 domain walls exist in the thermally annealed toroidal cores, but the domain walls exist in the thermally annealed toroidal cores, but the domain walls are not parallel to the longitudinal direction of the ribbon. In the specimen annealed with a magnetic field strength of 10 Oe in the longitudinal ribbon length axis, the domains are nearly parallel to the longitudinal direction due to the field induced uniaxial anisotropy resulting in further increase in the remanent magnetization and decrease in the coercive force and loss.

• Proceedings of the IEEK Conference
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• summer
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• pp.334-338
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• 2004

In this paper, we suggest a new antenna structure for RFID(Radio Frequency IDentification) reader. Conventional RFID reader uses a loop antenna. The central area of a loop antenna shows a low magnetic field strength especially for the case of a large loop antenna diameter. We propose a parallel-fed multiple loop antenna. Simulation results and measured results show that we can adjust field distribution with the number of turns and diameter of an inner loop antenna to obtain a longer reading distance. Simulation results for the specific case of a proposed antenna structure show that at the center point of a proposed parallel-fed multiple loop antenna, the typical card area averaged magnetic field strength is 2.53A/m, which is higher than the case of a conventional type single loop antenna of 0.44A/m and the case of a series-fed multiple loop antenna of 0.96A/m when we drive with same source signal. We realized the antenna for the case of 13.56MHz RFID reader and the performance of reading distance was much more improved than the case of a conventional antenna.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.484-492
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• 2010

Magnetic switch is a kind of saturable inductor, which utilizes nonlinearity of the magnetization curve of ferromagnetic materials. The right understanding of the saturation phenomena, magnetic properties, voltage-time product, and switching characteristics of the magnetic switch is essential in designing the magnetic pulse compressor (MPC). In this paper, the historical background of research on the MPC, fundamental physical properties of the magnetic switches, and application fields of the MPC are presented. Further, an in-depth analysis of pulse compression in series and parallel MPCs is incorporated. As practical application examples, a series MPC used for water treatments and a parallel MPC used for pulsed electric field (PEF) inactivation of bacteria are cited.

• Journal of Astronomy and Space Sciences
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• v.28 no.2
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• pp.117-122
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• 2011

In this paper, the anisotropic nature of the magnetic turbulence associated with magnetic dipolarizations in the Earth's plasma sheet is examined. Specifically, we determine the power spectral indices for the perpendicular and parallel components of the fluctuating magnetic field with respect to the background magnetic field, and compare them in order to identify possible anisotropic features. For this study, we identify a total of 47 dipolarization events in February 2008 using the magnetic field data observed by the THEMIS A, D and E satellites when they are situated near the neutral sheet in the near-Earth tail. For the identified events, we estimate the spectral indices for the frequency range from 1.3 mHz to 42 mHz. The results show that the degree of anisotropy, as defined by the ratio of the spectral index of the perpendicular components to that of the parallel component, can range from ~0.2 to ~2.6, and there are more events associated with the ratio greater than unity (i.e., the perpendicular index being greater than the parallel index) than those which are anisotropic in the opposite sense. This implies that the dipolarization-associated turbulence of the magnetic field is often anisotropic, to some non-negligible degree. We then discuss how this result differs from what the theory of homogeneous, anisotropic, magnetohydrodynamic turbulence would predict.

• Progress in Superconductivity
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• v.1 no.1
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• pp.68-72
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• 1999

Since the discovery of high Tc superconductors, great efforts have been focused to develop high performance HTS magnets for the ultimate applications to power system devices. Magnet designers, however, have had difficulties in the estimation of the maximum operating current of the designed magnet from the tested short sample data, due to the degradation of the critical current density in the magnet. Similar story applies to the HTS electrical bus bar. It has been found that the critical current of Bi-2223 stacked tapes is much less than the total summation of critical currents of each tape, which is mainly attributed to the self magnetic fields. Furthermore, since the critical current degradation of Bi-2223 tape is greater in the normal magnetic field (to the tape surface) than in the parallel one, detailed magnetic field configurations are required to reduce the self field effects. In this paper, we calculate the self field effects of a stacked conductor, defining self field factors of normal and parallel magnetic fields to the tape surface. Finally, the critical current degradations in the HTS magnet are explained by the introduced self field factors of the stacked conductor.

• Journal of the Korean Institute of Telematics and Electronics
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• v.6 no.1
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• pp.12-18
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• 1969

The characteristics of microwave reflection in the media of cold gaseous plasma is analysed to various external magnetic flux density. The DC discharge plasma is generated in the rectangular waveguide which contains two electrodes and helium gas at the pressure of 10-2mm Hg. The reflected and transmitted power of microwave is measured when the electric field is parallel to, and perpendicular to the external magnetic field. It shows that the reflected power is increased as the magnetic flux density is increased in the parallel case, but the maximum value of the reflected power is occured at the cyclotron resonance (3120 Gauss) in the perpendicular case.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.77-82
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• 2003

The ac loss is an important issue in the design of high-Tc superconducting power devices such as transformers and cables. In these devices many Bi-2223 tapes are closely stacked together and exposed to alternating magnetic fields that can have different orientations with respect to a tape. In such arrangement the magnetization loss is influenced by the screening current induced in adjacent tapes and thus different from that in a single tape. This stacking effect was experimentally investigated by measuring the magnetization loss in a stack, which consists of a number of tapes. First the magnetization loss in the single tape was measured in order to confirm the reliability of the loss data measured in the stack. The results for the single tape coincide well will the loss characteristics described in other previous works. For the stack In parallel and longitudinal magnetic fields the measured loss is Independent of both the number of tapes and stacking type. The longitudinal magnetization loss Is well explained rather by the slab model for decoupled filaments. For the tall stack in perpendicular field the measured loss at low fields is greatly decreased, compared to the loss of the single tape. However the loss at high fields is unaffected. These loss behaviors in the tall stack are well described by the slab model for full coupling.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.880-884
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• 2011

The matrix-type superconducting fault current limiter (MSFCL) consists of the trigger and current-limiting parts. The trigger part with reactors connected in parallel improves the quenching characteristics by applying the external magnetic field into the superconducting units. The current-limiting part with superconducting units connected in parallel and shunt reactors connected in series limit the fault current when the fault occurs. We developed the integrated reactor with the trigger and the current-limiting parts to apply high external magnetic field into the superconducting units. This was composed of a superconducting unit for the trigger part and two superconducting units for the current-limiting parts. We confirmed that the external magnetic field generated in the MSFCL with an integrated reactor was larger than that of the MSFCL with the separated reactors. So the differences of voltages generated between superconducting units were decreased in the difference according to the increment of the applied voltage. The whole magnitude of the SFCL was reduced because the volume of an integrated reactor could be reduced by one-third than that of the separated reactors. We confirmed that the critical behavior between the superconducting units in the MSFCL with an integrated reactor was more improved than that of the MSFCL with the separated reactors.