• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.326-329
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• 1997

This paper deals with the generating power analysis of wound rotor induction generator according to the rotor excitation for use of DFIG (Doubly Fed Induction Generator) system in wind power generation as a part of renewable energy development. In this way, the generating power of wound rotor induction generator can be achieved for a wide range wind speed of supersynchronous and subsynchronous speed.

• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.19-24
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• 2014

Development of long-term mobile energy sources for mobile robots or small-sized unmanned vehicles are actively increasing. The micro gas turbine generator (MTG) is a good candidate for this purpose because it has both of high energy density and high power density, and 500W class MTG is under development. The designed MTG can be divided into 2 main parts. One part consists of motor/ generator and compressor, and the other one consists of combustor, recuperator and turbine. 500W class MTG is designed to operate at ultra-high speed of 400,000 rpm in high turbine temperature over $700^{\circ}C$ to improve the efficiency. Because the magnetism of NdFeB permanent magnet for the motor/generator could be degraded if the temperature is over $150-200^{\circ}C$, MTG needs the thermal insulation to block the heat transfer from combustor/turbine side to motor/generator side. Moreover, the motor/generator is allocated to get the cooling effect from the rapid air flow by the compressor. This study presents the experimental results to verify whether the thermal insulator and air flow are effective enough to keep the motor/generator part in the low temperature less than $100^{\circ}C$. From the motoring test by using the high temperature test rig, it was confirmed that the motor/generator part could maintain the temperature less than $50^{\circ}C$ under the condition of 1.0 bar compressed air.

• Journal of the Korean Solar Energy Society
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• v.27 no.1
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• pp.1-9
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• 2007

This paper reveals both the operational situation and the cause of the error occurred in wind turbine generator system of Hangwon wind farm in Jeju island. The four wind turbines were selected for this work, and the monitored period was for six months. Wind resource in the wind farm was analyzed, and the estimated energy production was compared with the actual energy production. As a result, with a decrease of system error, the estimated energy production was in good agreement with the actual energy production. The errors occurring in components such as gearbox and hydraulic motor affected the Availability of the wind turbine. Also, poor external conditions such as a strong wind, lightning and gust caused a standstill of wind turbines.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.780-787
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• 2012

In general, the ocean wave vibration power generator consists of buoy, vibration system and linear generation system. It maximized energy efficiency by using resonance phenomenon that turned to the natural frequency of vibration system and frequency of ocean wave energy. But it is difficult to obtain efficiently energy from ocean wave because the frequency of ocean wave changes from moment to moment. In this paper, we study the buoy and vibration system of ocean wave power generator to solve these problem. Firstly, we designed the buoy that gives rise to resonance between ocean wave and buoy. Secondly, we designed vibration system that is occurred to resonance between buoy and vibration system. And then the relative velocity between the buoy and magnetic of ocean wave vibration generator increases and the relative displacement between buoy and ocean wave decreases at the same time. As a result, the method which is proposed in this paper has merits not only securing its stability from harsh ocean wave environment but also obtaining more kinetic energy from ever-changing ocean wave.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.5
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• pp.501-509
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• 2001

For the enhancement of ECT reliability on the primary water stress corrosion cracks of nuclear steam generator tubes, of which the occurrence is on the increase, it is important to comprehend the signal characteristics on crack morphology and to select an appropriate probe type. In this paper, the sizing accuracy and the detectability for the inner wall axial cracks of tubes were quantitatively evaluated using the following specimens: the electric discharge machined notches and the corrosion cracks which were developed on the operating steam generator tubes. The difference of eddy current signal characteristics between pancake and axial coil were also Investigated. The results obtained from this study provide a useful information for more precise evaluation on the inner wall axial tracks oi stram generator tubes.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.174-181
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• 2014

Design procedure of LEG(Linear Electric Generator) is introduced by performing the time-domain analysis for the heaving motion of a floating buoy coupled with LEG. A vertical truncated buoy is selected as a point absorber and a double-sided Halbach array mover and cored slotless stator is adopted as a linear electric generator. LEG with a double-sided Halbach array mover and cored slotless stator is designed with the input data such as the heave motion velocity and wave exciting forces in time-domain. The validity of designed LEG is confirmed by performing generating-characteristic-analysis under the sinusoidal motion of a buoy, based on the numerical techniques such as FE(Finite Element) analysis. In particular, an ECM(Equivalent Circuit Method) is employed as the design tool for the prediction of generating characteristics under irregular wave conditions. Finally, we confirm that the ECM gives reasonable and fast results without sacrifice of accuracy.

• Nuclear Engineering and Technology
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• v.39 no.3
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• pp.231-236
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• 2007

Due to the occasional occurrences of stress corrosion cracking(SCC) in steam generator tubing(Alloy 600), degraded tubes are removed from service by plugging or are repaired for re-use. Since electrodeposition inside a tube does not entail parent tube deformation, residual stress in the tube can be minimized. In this work, tube restoration via electrodeposition inside a steam generator tubing was performed after developing the following: an anode probe to be installed inside a tube, a degreasing condition to remove dirt and grease, an activation condition for surface oxide elimination, a tightly adhered strike layer forming condition between the electro forming layer and the Alloy 600 tube, and the condition for an electroforming layer. The reliability of the electrodeposited material, with a variation of material properties, was evaluated as a function of the electrodeposit position in the vertical direction of a tube using the developed anode. It has been noted that the variation of the material properties along the electrodeposit length was acceptable in a process margin. To improve the reliability of a material property, the causes of the variation occurrence were presumed, and an attempt to minimize the variation has been made. A Ni alloy electrodeposition process is suggested as a primary water stress corrosion cracking(PWSCC) mitigation method for various components, including steam generator tubes. The Ni alloy electrodeposit formed inside a tube by using the installed assembly shows proper material properties as well as an excellent SCC resistance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.9
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• pp.1083-1090
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• 2011

A steam generator poses many difficulties during the development of a sodium-cooled fast reactor because of the sodium-water-reaction problems. Until now, several types of steam generators have been developed, but the specifications of these generators differed in each country. Moreover, even if a country had developed a steam generator, it was not used in the subsequent reactor because the current techniques were not stabilized to select the proper steam generator. As a common development, the Benson steam cycle with few welding locations and high economical efficiency may be adopted. Moreover, the design is dwelled on the convenience of inspection, detection, control, and maintenance for the wear caused by sodiumwater reactions. The specifications of the designed steam generators were reviewed and the current technical problems for steam generators were analyzed. Concepts were proposed to overcome the current technical problems for steam generators.

• Corrosion Science and Technology
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• v.3 no.1
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• pp.30-33
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• 2004

It has been reported that some events of a rupture of seam generator tube have occurred in nuclear power plants around the world. Main causes of the leakage are from various types of corrosion in the steam generator(SG) tubings. Primary water stress corrosion cracking(PWSCC) of steam generator tubings have occurred in many tubes in Korean plant, and they were repaired using sleeves or plugs, In order to develop proper repair criteria, it is necessary to ascertain the leak behavior of the tubings. A high pressure leak and burst testing system was manufactured. Various types of Electro Discharged Machined (EDM) notches were developed on the SG tubes. Leak rate and burst pressure were measured on the tubes at room temperature. Burst pressure of the part through wall defected tubes depends on the defect depth, Water flow rates after the burst were independent of the t1aw types; tubes having 20 to 60 mm long EDM notches showed similar flow rates regardless of the defect depth. A fast pressurization rate gave the tube a lower burst pressure than the case of a slow pressurization.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.12
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• pp.785-790
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• 1999

This research has been carried out to develop a low-energy large-aperture pulsed electron beam generator (LELA), 200keV 1A, for industrial applications. One of the most important feature of this electron beam generator is large electron beam cross section of $190cm^2$. Low energy electron beam generators have been used for water cleaning, flue gas cleaning, and pasteurization, etc. In these applications the cross sectionof the e-beam is related to reaction efficiency. Another important feature of this LELA EB generator is easy maintenance because of its simple structure and relatively low vacuum operation compared to the conventional EB generators. The conventional EB generators need to be scanned because the small cross section thermal electron emitters are used in the conventional EB generators which have small EB cross section. In this research, we use the secondary electrons generated by ion bombardment on the HV cathode surface as a electron source. Therefore we can make any shape of EB cross section without scanning.