• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2128-2135
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• 2009

In this paper, current limiter using a magnetic switching which is based on magnetic flux change in the case of fault is proposed. This current limiter consists of iron-core and three parts of coils. One is the primary coil connected to the power system. Another is the secondary coil wound to the opposite direction of the primary coil's winding. The other is the secondary of the secondary coil which is a movable copper plate winding and located below the secondary coil. In the normal state, the magnetic flux produced in the primary and secondary coils flows to the opposite directions each other and becomes to be canceled out. Therefore the voltages induced between the coils are zero. In the case of a fault, at the moment of a fault occurrence recognition, the switch connected to a secondary coil is opened and the secondary of the secondary coil is pulled out to the outside of the iron-core. Then, magnetic flux becomes to flow through the iron-core. Accordingly, the voltage is induced between the both ends of the primary coil and makes the current reduced. Therefore it is possible to cut off the circuit breaker easily with the proposed current limiter. This paper analyzes the current limiting effects and the detailed results are given.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.856-862
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• 2005

A flux-lock type SFCL consists of two coils, which are wound in parallel each other through an iron core, and a HTSC thin film connected in series with coil 2. If the current of the HTSC thin film exceeds its critical current by the fault accident, the resistance generated of the HTSC thin film, and thereby the fault current can be limited by the impedance of the flux-lock type SFCL. The amplitude of fault current can be set by the impedance of the flux-lock type SFCL. In this paper, we investigated the variance of the limiting current due to the ratio of inductances between coil 1 and coil 2 in the flux-lock type SFCL through the computer simulations and short circuit tests. In addition, both the simulation results and experimental ones were compared each other. From the comparison of both the results, the simulation results agreed well with the experimental ones.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.522-525
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• 2009

We investigated the fault current characteristics of the separates three-phase flux-lock type superconducting fault current limiter(SFCL) according to the variation of inductances. The single-phase flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil on an iron core. And superconductor is series connected on secondary coil. Superconductor is using the YBCO coated conductor. The separated three-phase flux-lock type SFCL consists of single-phase flux-phase type SFCL in each phase. To analyze the current limiting characteristics of a three-phase flux-lock type SFCL, the short circuit experiments were carried out fault such as the triple line-to-ground fault. The experimental result shows that fault current limiting characteristics of additive polarity winding was better than subtractive polarity winding and when the inductances of coil 2 was lower, resistances of YBCO CC was more generated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.9
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• pp.714-717
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• 2010

The improved flux-lock type superconducting fault current limiter (SFCL) is composed of a series transformer and superconducting unit of the yttrium-barium-copper-oxide (YBCO) coated conductor. In this paper, we investigated current limiting characteristics through winding direction of coil 2 and variable number of coil 1 and coil 2 in improved flux-lock type SFCL. The better fault current characteristics and the burden of YBCO coated conductor can be confirmed from the experimental result in the higher turn ratio of coil 1 and coil 2 in the additive conditions. In case of subtractive condition, we can confirm a similar result in the same case of experimental conditions. but the burden of YBCO coated conductor has been increased from an increase in winding numbers of coil 2.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.12B no.1
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• pp.13-18
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• 2002

Novel method to calculate flux linkage for 3-D finite element analysis is proposed. It does not require any integral path if the current direction in a coil is known. The flux linkage can be calculated very easily using simple volume based integration. The current direction is calculated based on the recently developed technique by the authors. The novel method for flux linkage calculation is verified by applying to a very complicated deflection yoke coil. The simulation result is compared to the experimental one. From the simulation, it is shown that the proposed method is very accurate and effective to calculate the flux linkage of a coil.

• Progress in Superconductivity and Cryogenics
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• v.3 no.2
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• pp.15-20
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• 2001

This paper describes a model flux pump experiment recently performed at the MIT Francis Bitter Magnet Laboratory. The results of the model flux pump will be used in the development of a prototype flux pump that will be couple to a high-temperature superconductor (HTS) insert coil of a high-field NMR (Nuclear Magnetic Resonance) magnet, Such an HTS insert is unlikely to operate in persistent model because of the conductors low index(n) The flux pump can compensate fro field decay in the HTS insert coil and make the insert operate effectively in persistent mode . The flux pump, comprised essentially of a transformer an two switches. all made of superconductor, transfers into the insert coil a fraction of a magnetic energy that is first introduced in the secondary circuit of the transformer by a current supplied to the primary circuit. A model flux pump has been designed. fabricated, and operated to demonstrate that a flux pump can indeed supply a small metered current into a load superconducting magnet. A current increment in the range of microamperes has been measured in the magnet after each pumping action. The superconducting model flux pump is made of Nb$_3$ Sn tape, The pump is placed in a gaseous environment above the liquid helium level to keep its heat dissipation from directly discharged in the liquid: the effluent helium vapor maintains the thermal stability of the flux pump.

• Journal of Mechanical Science and Technology
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• v.16 no.11
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• pp.1540-1549
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• 2002

Experimental results are presented for the effects of coil diameter, system pressure and mass flux on dryout pattern of two-phase flow in helically coiled tubes. Two tubes with coil diameters of 215 and 485 mm are used in the present study, Inlet system pressures range from 0.3 to 0.7 MPa, mass flux from 300 to 500 kg/㎡s, and heat flux from 36 to 80 kw/㎡. A partial dryout region exists because of the geometrical characteristics of the helically coiled tube. The length of the partial dryout region increases with coil diameter and system pressure. On the other hand, it decreases with increasing mass flux. The critical quality at the tube top side increases with mass flux, but decreases with increasing system pressure. This tendency is more notable when the coil diameter is larger. When the centrifugal force effect becomes stronger, dryout starts at the top and bottom sides of the tube. However, when the gravity effect becomes stronger, dryout is delayed at the tube bottom side. In some cases when the mass flux is low, dryout occurs earlier at the outer side than at the inner side of the tube because of film inversion.

• Progress in Superconductivity
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• v.4 no.1
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• pp.68-73
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• 2002

We have fabricated YBCO SQUID 1st order gradiometers on $30^{\circ}$STO bicrystal substrate. The pickup coil size was 3.8mm$\times$3.8mm and baseline was 5mm. Three types of SQUID gradiometer were designed and tested for unshielded operation; solid pickup coil, pickup coil consisting of 4 parallel $ 50\mu\textrm{m}$-wide loops, and solid pickup coil with flux dam. We have investigated external magnetic field dependence of the SQUID gradiometers on the magnetic field noiseproperties. Significant increase of low frequency noise with the application of static field has been observed in the case of parallel and flux dam type pickup coil above threshold field of $1.3 \mu$T. Magnetic field noise at 1 Hz measured in the magnetically shielding room was 30, 165, 480 fTcm／sup -1／Hz／sup -1/2／ for solid type and slot type and parallel loops type, respectively.

• Journal of electromagnetic engineering and science
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• v.8 no.1
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• pp.23-27
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• 2008

Magnetic coupling delivering wireless power in capsular endoscope(CE) is described in this paper. The characteristic of the magnetic flux linkage coil which generates the induced electromotive force(emf) under the magnetic field was analyzed. With the analyzed results, a magnetic flux linkage coil system was developed and tested. It was confirmed that the magnetic flux linkage coil system could supply more than 50 mW power at 125 kHz without changing the structure of conventional CE.

• Journal of Magnetics
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• v.21 no.2
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• pp.222-228
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• 2016

Correlation between coil configurations and the discharge characteristics such as plasma density and the electron temperature in a newly designed magnetized inductively coupled plasma (M-ICP) etcher were investigated. Radial and axial magnetic flux density distributions as well as the magnetic flux density on the center of the substrate holder were controllable by placing multiple circular coils around the etcher. The plasma density increased up to 60.7% by arranging coils (or optimizing magnetic flux density distributions inside the etcher) properly although the magnetic flux density on the center of the substrate holder was fixed at 7 Gauss.