• Journal of Biomedical Engineering Research
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• v.13 no.3
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• pp.217-224
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• 1992

A new three-channel surface gradient coil obtained by using numerical optimization and its application to MR computerized nomography are presented. The new surface gradient coil pro aided linear field gradient region more than twice wider compared with the t'irst surface gradi encl coil, removed torque and field offset, and reduced coupling between the surface gradient coil and combined surface rf coil. We realized the new surface gradient coil set with $30{\times}60{cm^2}$2 size, which generated more tharl 4G/cm with 100 amperes over a $4{\times}4{\times}4{cm^3}$ region with good linearity. The optimal geometries of the three-channel surface gradient coil and volun teer's high-resolution in wiuo spinal cord Images obtained by using the optimized surface gradi ent coil set are presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.689-693
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• 2009

We investigate the comparison of fault current characteristics between the separates three-phase flux-lock type superconducting fault current limiter(SFCL) and integrated three-phase flux-lock type superconducting fault current limiter(SFCL). 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 superconducting elements are connected to secondary coil in series. Superconducting elements are used by the YBCO coated conductor. The separated three-phase flux-lock type SFCL consists of single-phase flux-phase type SFCL in each phase. But the integrated three-phase flux-lock type SFCL consists of three-phase flux-reactors wound on an iron core. Flux-reactor consists of the same turn's ratio between coil 1 and coil 2 for each single phase. To compare the current limiting characteristics of the separated three-phase flux-lock type SFCL and integrated three-phase flux-lock type SFCL, the short circuit experiments are carried out fault condition such as the single line-to-ground fault. The experimental result shows that fault current limiting characteristic of the separated three-phase flux-lock type SFCL was better than integrated three-phase flux-lock type SFCL. And the integrated three-phase flux-lock type SFCL has an effect on sound phase.

• Journal of Power Electronics
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• v.19 no.1
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• pp.211-219
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• 2019

In magnetically coupled resonant (MCR) wireless power transfer (WPT) systems, the introduction of additional intermediate coils is an effective means of improving transmission characteristics, including output power and transmission efficiency, when the transmission distance is increased. However, the position of intermediate coils in practice influences system performance significantly. In this research, a three-coil MCR WPT system is adopted as an exemplification for determining how the spatial position of coils affects transmission characteristics. With use of the fundamental harmonic analysis method, an equivalent circuit model of the system is built to reveal the relationship between the output power, the transmission efficiency, and the spatial scales, including the axial, lateral, and angular misalignments of the intermediate and receiving coils. Three cases of transmission characteristics versus different spatial scales are evaluated. Results indicate that the system can achieve relatively stable transmission characteristics with deliberate adjustments in the position of the intermediate and receiving coils. A prototype of the three-coil MCR WPT system is built and analyzed, and the experimental results are consistent with those of the theoretical analysis.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.46-51
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• 2002

Recently, High capacity alternator are used fur some special equipments in industry. But, several serious problem are occured, especially, broken coil of rotor, caused by crash with stator on rotating the rotor. Although added coil cover thor protect coil of rotor, coil cover is broken. In this study purpose 2 step for corrected that problems. First, three dimensional finite element method far investigate what is most important point. For that purpose, performed stress analysis of coil and coil cover that modeling and finite analysis by ANSYS software. Second, Apply prestress when winding the coil on stator to modify direction of net force. Vector analysis is used for determine corrected prestress. Result of the analysis and prestress are reviewed.

• 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 Power Electronics
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• v.18 no.2
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• pp.533-546
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• 2018

This study proposes a comprehensive mathematical model that includes coil-system circuit and loss models for power converters in wireless power transfer (WPT) systems. The proposed model helps in understanding the performance of WPT systems in terms of coil-to-coil efficiency, overall efficiency, and output power capacity and facilitates system performance optimization. Three methods to achieve constant output power for variable-load systems are presented based on system performance analysis. An optimal method can be selected for a specific WPT system by comparing the efficiencies of the three methods calculated with the proposed model. A two-coil 1 kW WPT system is built to verify the proposed mathematical model and constant output power control methods. Experimental results show that when the load resistance varies between 5 and $25{\Omega}$, the system output power can be maintained at 1 kW with a maximum error of 6.75% and an average error of 4%. Coil-to-coil and overall efficiencies can be maintained at above 90% and 85%, respectively, with the selected optimal control method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.167-168
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• 2005

The operational characteristics of the integrated three-phase flux-lock type superconducting fault current limiter (SFCL) were analyzed. The suggested three-phase SFCL consisted of a three-phase flux-lock reactor and three high-Tc superconducting (HTSC) elements. The former has three windings wound on an iron core, each of which has the same turn's ratio between coil 1 and coil 2. The latter are connected in series with coil 2 of each phase. The integrated three-phase flux-lock type SFCL showed the operational characteristics that the fault phase could affect the sound phase, which resulted in quenching the HTSC element in the sound phase. Through the computer simulation applying numerical analysis for its three-phase equivalent circuit, the fault current limiting characteristics of the integrated three-phase flux-lock type SFCL according to the ground fault types were compared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.112-113
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• 2006

The operational characteristics of the integrated three-phase flux-lock type superconducting fault current limiter (SFCL) were analyzed. The suggested three-phase SFCL consisted of a three-phase flux-lock reactor and three high-$T_c$ superconducting (HTSC) elements. The former has three windings wound on an iron core, each of which has the same turn's ratio between coil 1 and coil 2. The latter are connected in series with coil 2 of each phase. The integrated three-phase flux-lock type SFCL showed the operational characteristics that the fault phase could affect the sound phase, which resulted in quenching the HTSC element in the sound phase. Through the computer simulation applying numerical analysis for its three-phase equivalent circuit, the fault current limiting characteristics of the integrated three-phase flux-lock type SFCL according to the ground fault types were compared.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.3
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• pp.101-106
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• 2003

The high temperature superconductor transformers gain interests from the industries. This paper described construction and test results of 10㎸A HTS transformer Three phase transformer with double pancake windings were constructed. To reduce the leakage magnetic field, secondary coil were placed between the two primary coils. BSCCO-2223 wire. silicon sheet steel core and FRP cryostats were used to construct the transformer. Three coils were stacked in one cryostat. Two double pancake coils were connected in series for the primary coil and one double pancake coil was used for the secondary coil. Total number of turns of the primary winding and the secondary winding were 112turns and 98urns, respectively, The rated voltages of each winding were 440/220V. The rated currents of each winding were 13.1/26.2A. After the tests of basic properties of the three phase HTS transformer using no-load test, short-circuit test and full-load test, continuous operation of 100 hours with pure resistive load has been carried out. Test results proved over-load capability and reliability of the HTS transformer.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.727-730
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• 2007

Coil inductor has been used widely as an electromagnet, because of the high magnetic filed resulting from the voltage applied to the coil. In this study the coils were used in vibration suppression as an actuator. The control system consists of a coil attached in aluminum beam and a permanent magnet set at its bottom. This actuation method is easy to be incorporated into the system and allows significant forces to be applied without contacting with the structure. Three types of coils (cylindrical type, square type, Circular sheet type) were employed in vibration suppression of cantilever beam. The positive position feedback (PPF) controller was applied to the magnet-coil actuator to suppress the first mode of vibration. Experimental results showed that the cylindrical type and square type coil made good vibration suppression efficiency under PPF controller than their eddy current damper. However, there was minimal difference for the circular sheet type coil if compared with its eddy current damper.