• Journal of Power System Engineering
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• v.13 no.6
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• pp.95-101
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• 2009

The generator for gas turbine power generation consists of the rotor which generates magnetic field, the winding coil which is the path for the field current and the wedge and retaining ring which prevents the radial movement of the coil. Relatively severe deformation was observed at the coil end section during the inspection of the generator for peaking-load operation, and the thermal-electricity and the centrifugal force were evaluated by the simple modeling of the windings to find the cause. But the simulation stress was not sufficient to induce the coil plastic deformation. The analysis result seems to be applicable to the base-load generators which runs continuously without shut down up to a year, but there had been more deformation than simulated for the generator which is started up and shut down frequently. The cause of the coil deformation was the restriction of the expansion and shrinkage. The restriction occurs when the winding coil shrinks, and the stress overwhelms the yield stress and cause the plastic deformation. The deformation is accumulated during the start-ups and shut-downs and the thermal growth occurs. The factors which induce the coil restriction during the expansion and shrinkage should be reduced to prevent the unallowable deformation. The resolutions are cutting off the field current earlier during the generator shut-down, modifying the coil end section to remove the stress concentration and making the insulation plate inserted between the coil end section and the retaining ring have the constant thickness.

• Journal of Digital Contents Society
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• v.11 no.3
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• pp.283-290
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• 2010

The effectiveness of 3.0T phase array coil images was tested by comparing signal-to-noise ratios for the same coil images relative to 1.5T endorectal coil images. Signal intensities were measured in the three regions of prostate, central and peripheral (right and left) after 40 patients with prostate cancer were imaged during the period between Jan. 2008 and Oct. 2009 with T2 W, T1 W, and DW images obtained respectively using endorectal coil on a 1.5T MR scanner and phase array coil on a 3.0T MR scanner. For quantitative analysis, comparisons of average SNRs for the same ROIs were made between groups scanned with a 1.5T and a 3.0T MR scanner. The signal-to-noise ratios were shown to increase more sharply when using a phase array coil at a 3.0T MR scanner compared to using an endorectal coil at a 1.5T MR scanner.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.3
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• pp.1302-1307
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• 2011

The Spiral coil is made considering primary, secondary side coil inductance, turn number, size, thickness, and shielding area with the litz wire-type in case of manufacturing a coil, and at this time, the semi-automation winding machine is used. When deciding on primary and secondary side coil specification and manufacturing a coil, the spiral coil of a specification varied in the various litz wire of a specification is required, and at this time, a difficulty is generated by the manufacture cost, period which during, and failure the manufacture is generated in the coil sample making. A difficulty is in the desired coil quality control of a specification. Since improving the rectifier of the secondary side in order to improve this kind of problem, the range of the coil design and the during the manufacture, various coil manufacture specifications can be comprehensively made.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.78-84
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• 2010

The efficiency of system with a built-in coil is improved as (1) the total coil flux increases, (2) the space distribution of coil flux is closer to the sinusoidal wave and (3) the direction of coil flux flow becomes more inherent with the original direction at the same condition. Every turn RC(Reinforced Coil) is composed of OC having original region and two IC's strengthening bidirectionally the inner part flux in order to maintain the symmetry with origin. This way we will realize the inherent flux direction and the sinusoidal closeness as well. Accordingly RC type is obtained by connecting the pure OC's and RC's in just turns to be closer to sinusoidal flux wave. We proved experimentally the usefulness of reinforced coil to improve the efficiency of SPIM.

• Journal of Magnetics
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• v.20 no.3
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• pp.308-311
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• 2015

We design a crisscrossed double-layer birdcage (DLBC) coil by modifying the coil geometry of a standard single-layer BC (SLBC) coil to enhance the homogeneity of transmitting magnetic flux density ($B_1{^+}$) along the main magnetic field ($B_0$)-direction for small-animal magnetic resonance imaging (MRI) at 300 MHz. The performance assessment of the crisscrossed DLBC coil is conducted by computational analysis with the finite-difference time domain method (FDTD) and compared with SLBC coil in terms of the $B_1$ and the $B_1{^+}$ distribution. As per the computational calculation studies, the mean value in the two-dimensional $B_1{^+}$ map obtained at the mid-axial slice with the proposed DLBC coil is slightly lower than that obtained with the SLBC coil, but the $B_1{^+}$ value of the DLBC coil in the outermost plane (40 mm away from the central plane) shows improvements of 19.3% and 24.8% over the SLBC coil $B_1{^+}$ value when simulating a spherical phantom and realistic mouse body modeling. These simulation results indicate that, the $B_1{^+}$ homogeneity along the z-direction was improved by using DLBC configuration. Our approach enables $B_1{^+}$ homogeneity improvement along the zdirection, and it can also be applied to ultra-high field (UHF) MRI systems.

• Journal of Magnetics
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• v.18 no.4
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• pp.481-486
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• 2013

An electromagnetic launcher (EML) system accelerates and launches a projectile by converting electric energy into kinetic energy. There are two types of EML systems under development: the rail gun and the coil gun. A railgun comprises a pair of parallel conducting rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail, but the high mechanical friction between the projectile and the rail can damage the projectile. A coil gun launches the projectile by the attractive magnetic force of the electromagnetic coil. A higher projectile muzzle velocity needs multiple stages of electromagnetic coils, which makes the coil gun EML system longer. As a result, the installation cost of a coil gun EML system is very high due to the large installation site needed for the EML. We present a coil gun EML system that has a new structure and arrangement for multiple electromagnetic coils to reduce the length of the system. A mathematical model of the proposed coil gun EML system is developed in order to calculate the magnetic field and forces, and to simulate the muzzle velocity of a projectile by driving and switching the electric current into multiple stages of electromagnetic coils. Using the proposed design, the length of the coil gun EML system is shortened by 31% compared with a conventional coil gun system while satisfying a target projectile muzzle velocity of over 100 m/s.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.9
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• pp.640-646
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• 2007

The cooling heat transfer coefficient of $CO_2$ (R-744) for tube and coil diameter (CD), inclined angle of tube and coil pitch of inclined helical coil type copper tubes were investigated experimentally. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55 mm inner diameter (ID). The refrigerant mass flukes were varied from 200 to 800 [$kg/m^2s$] and the inlet pressures of gas cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in inclined helical coil tube with 2.45 mm ID are $5{\sim}10.3%$ higher than those of 4.55 mm. The heat transfer coefficients of 41.35 mm CD are $8{\sim}32.4%$ higher than those of 26.75 mm CD. Comparison between $45^{\circ}\;and\;90^{\circ}$ of coil angle, the heat transfer coefficients of $45^{\circ}$ are higher than those of $90^{\circ}$. For coil pitch of gas cooler, the heat transfer coefficients of inclined helical coil gas cooler with coil pitch of 5 mm are similar to those of 10 and 15 mm.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.34 no.1
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• pp.38-43
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• 1985

Since the superconductor type II with high critical current and high critical magnetic field was discovered in 1961, there were many studies on the superconducting coil for high field and highly homogeneous field. The graphical method and the numerical method by Newton Raphson technique have been studied as the method for design of homogeneous superconducting coil. It is comparatively easy to get a compensating coil for any given main coil by the above methods, but it is too laborious to get a general solution for main coil dimension. This paper studies the optimal design method for minimum volume of superconducting coil under certain central field and highly homogeneous field. The present method makes use of the nonlinear programming for optimization. The optimal solution of NMR superconducting coils by this method are demonstrated very well.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1996.10b
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• pp.181-189
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• 1996

회전열파이크는 전기모터, 고온가스터빈 등의 냉각에 이용함으로써 성능개선을 얻을 수 있다는 점에서 지난 20년 동안 많은 연구가 이루어져왔다. 그동안 내부벽면형상개발은 Taper를 설치하거나, 계단식 단면변화 또는 Impeller설치와 같은 기술들이 연구되었다. 본 연구는 회전 열파이프 용기내벽에 Coil Insert를 설치하여 응축액막 유동효과에 대한 가시화실험 및 열전달 성능실험을 통하여 그 특성을 검토하였고 아래와 같은 결과를 얻을 수 있었다. 1) Pool 영역에서는 Coil Insert에 의한 축방향 펌프효과가 매우 크며, 그 효과는 나선각이 클수록 크게 나타난다. 2) Coil Insert는 Pool에서 환상류로 천이를 촉진시키며, 나선각이 클수록 그 효과가 크게 나타난다. 3) Coil insert 열파이프의 열저항에 미치는 효과는 크지 않은 것으로 보인다. 4) Coil Insert에 의해 Dry-out한계의 증가가 예상되지만, 실험장치의 열부하한계에 의해 확인할 수 없었다.

• Journal of the Korean Society of Industry Convergence
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• v.9 no.1
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• pp.67-72
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• 2006

This study is on the development of algorithm of surge test for quality control on electrical parts of throttle body in automobiles with internal combustion engine, not only to know its condition to be good or not, but also jugding its condition to be classified into six types. To know whether its condition to be good or not, comparing and analyzing between two waveforms generated from master and test coil of throttle body. If test net area is below 20% of master area, the condition of test coil is good. By analyzing test coil waveform to master coil waveform, the condition of test coil into winding badness, insulation badness, layer and corona discharge, short badness should known. Therefore quality control system on electrical parts of throttle body should be developed.