• Proceedings of the KIEE Conference
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• 2005.07e
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• pp.73-75
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• 2005

In present measurement of moisture contents is used as one of method for estimating degradation of transformer. Most of people use Karl-Fischer titration method for detection moisture contents but this measurement is inconvenient method because we must analyze transformer oil-paper after dismounting transformer and sampling in field. Therefore we don't directly investigate them in field. In this paper we will introduce Recovery Voltage Method(RVM) that is new method for estimating measurement in field though dismounting facility. For measure of moisture contents using RVM in accordance with accelerated thermal aging we have made experimental test cell and aged at a temperature up to 140$^{\circ}C$ for 300 hours. And we have been measured at intervals of 100 hours using RVM 5462 made in fetter company.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.7-9
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• 2003

A 3MJ class SMES was fabricated last year. And 1000A class current part for the SMES also was designed, fabricated and tested. The current lead was made of metal part(brass) and HTS lead Part. The lead is located in vacuum vessel and cooled down to belows the HTS lead's operating temperature. We made three types of current lead part and tested their performance. In this paper, the basic and conceptual type of current lead will be introduced. The lead was expected to have 1000A current capacity. But the test results was only 480A. After this test, based on the results we revised the shape of the lead and improved the connectivity between cryocooler and lead. In this paper, the design procedure and the results of performance test will be introduced.

• Journal of IKEEE
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• v.17 no.2
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• pp.159-162
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• 2013

In this paper, we make a performance analysis of two kinds of platforms, JAVA and .NET, about SOAP(Simple Object Access Protocol). SOAP is able to use various transport layer protocol but in this paper we suggested methods of performance analysis with using HTTP, TCP, UDP and then we made an performance analysis on the basis of suggested methods. The results of performance analysis may be deduced differently by a system environment and loaded degree of network. Therefore, for precise performance analysis, we made same environment and proceeded.

• Journal of the Korea Safety Management & Science
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• v.13 no.1
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• pp.1-9
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• 2011

It is a significant issue for several country including Korea, where the natural and the weather conditions are severe, to keep the safety against disasters which occur frequently every year, especially in urban region crowded with population. In order to implement suitable and effective measures against various disasters in such area, development of method for evaluation of disaster prevention performance based on various disaster risks and effective disaster damage mitigation technologies is independable. In this paper, methods for hazard evaluation, vulnerability evaluation and loss evaluation, and damage technologies are proposed targetting man-made disaster and natural one like flood, earthquake and tsunami and so on. The method proposed in this paper is based on the research of USA and Japan for man-made disaster and natural disaster. The proposed method will be developed in detail in four years during research period funded by government.

• Proceedings of the KIEE Conference
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• summer
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• pp.1046-1048
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• 2004

Inductance is an important parameter determining the characteristics of current waveform in electric motors. There are many kinds of inductances, however, self and mutual inductances are the major components. These inductances are changed under the variation of the magnetic circuit, current, frequency etc., even in the same winding distribution. Therefore this paper deals with the characteristics of inductance according to the shape of stator tooth. The analysis model is newly developed motor made of SMC(Soft Magnetic Composite) to reduce the core loss in high speed. the result of this paper gives the basic understandings of inductance to extend the applications of the motors.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.4
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• pp.272-281
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• 2000

This paper deals with the parallel operation of several numbers of PWM converters for a high speed railway train application. Several considerations are made to reduce the transformer interaction which can cause a current control problem in severe case. Also, in this paper, novel control strategy is proposed to achieve a harmonic free primary-side current control under a light load condition using one current sensor independent of the number of converters. In addition, the modified predictive current controller, which is suitable to a digital current controller with a relatively large sampling period, is used. Finally, to verify the system validity, digital control system with TMS320C44 micro-processor and small scale simulator are made and tested.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.687-693
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• 2011

In this paper, problems and solutions are proposed for applying IEC 61850 to Distribution Automation System(DAS). Communication protocol integration in power automation system have issued by IEC standards, IEC 61850 of them has researched for applying IEC 61850 to many areas of power system in spite of that it was made for substation automation system. Especially, DAS is just about to apply IEC 61850 by communication network change from serial to ethernet although DNP 3.0 is used. But it's impossible to apply directly IEC 61850 to DAS by difference of environment which unfixed wide area and separated nodes in power distribution system unlike concept of IEC 61850 is made by Substation Automation System(SAS) environment of limited space. Thus, this paper proposed applications of three types which conceptual, practical, and future to consider problems and solutions when apply IEC 61850 to Ethernet based DAS.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1291-1293
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• 2005

Switched reluctance motors have the advantage a high torque/weight ratio, as the large reluctance torque is made by salient poles of both stator and rotor, and a high reliability. On the other hand, the switched reluctance motors have the disadvantage of a large ripple torque which is made by salient poles. So the application for the industrial fields have been limited to special cases. This paper describes the design of a 12/8 switched reluctance motor using a enemy layer method of the asymmetry rotor. The design is focussed to reduce the torque ripple and radial force in the demanded value. The three dimension finite element analysis method(3D-FEM) was used for decides a enemy layer angle of the asymmetry rotor. This paper presents modifications of the rotor pole shape which reduces the torque ripple.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.62-67
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• 1999

The RP&M(Rapid Prototyping and Manufacturing) is the most appropriate technology for the small-lot production system, in which the production cycle is getting shorter owing to various needs from consumers. Recently RP products which are made of plastics, wax, and paper are used to verify the design of samples. But these products cannot be applied to the real mold because the strength enough to be a mold cannot be given by soft materials such as plastics. So RP products are copied to AFR(Al powder Filled Resin) molds or metal molds, which is called the RP&M. In this paper, RP&M is applied to a casting process. A porous casting mold, which is made from ceramic powder and binder, is used for rapid tooling of aluminum shoes molds.

• Advances in concrete construction
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• v.4 no.1
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• pp.27-35
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• 2016

The quantity of construction and demolition waste has been greatly increasing recently. It causes many problems to the environment. For this reason, demolition waste management becomes inevitable in order to overcome the environmental issues. The present study aims to evaluate the effects of using recycled coarse aggregate, which is generated from construction and demolition waste, on the properties of recycled aggregate concrete. An experimental investigation on the strength characteristics of concrete made with recycled coarse aggregate is presented and discussed in this paper. In this study, Portland Pozzolana Cement (fly ash based) is used instead of ordinary Portland cement. The results of this investigation show the possibility of the use of recycled coarse aggregates in the production of fresh concrete. Use of demolition waste as coarse aggregate will lead to a cleaner environment with a significant reduction of the consumption of natural resources. A comparative study on the strength characteristics of recycled aggregate concrete made with Ordinary Portland Cement and Portland Pozzolana Cement is presented and discussed in this paper.