• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.660-664
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• 2004

The indirect rotor position detection method using terminal voltage of brushless DC motor (BLDCM) requires simple control circuit, and has wide speed range of sensorless operation. However, because the substantial phase difference exists between real back emf and terminal voltage, the existing indirect detection method using analog filter which is affected by frequency, speed, and load sensitively cannot be synchronized with current, in the end, it advances or delays. This paper presents new analog filter circuit design for rotor position estimation in order to solve the problem, and proposes novel sensorless operation method which is stable even in high speed range and not influenced by parameters with analysis on phase difference by load and speed. Moreover, the appropriateness of the proposed sensorless drive in this paper is verified and analyzed by experimentation.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.250-252
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• 2008

An inductor-capacitor-inductor (LCL) filter are widely adapted in grid-connected inverter applications. In this paper, the harmonic attenuations of the LCL filter are quantitatively analyzed, and then the design optimization of two inductance values, which are related on a cost and a size, is illustrated. Based on the design optimization, the LCL filter employing a Symmetric Geometry is proposed. Through the equivalent circuit analysis of the proposed LCL filter, the operating characteristics and validity are presented in detail. In addition, simple proportional-integral (PI) current controller suitable for the LCL Filter is designed to mitigate the resonance problem. From simulation results, it is seen that the proposed LCL filter and control method have a sufficient attenuation and stability for the high frequency distortions and load variations.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.144-150
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• 2006

A serious problem with traditional 'command & control' spectrum management techniques is that they do not easily accommodate new technologies and new services. This paper describes the necessary principles of flexible-use spectrum rights which may allow a wide variety of spectrum uses in a single general-purpose band. Based on the electrospace description of the radio spectrum, these principles allow general aggregation or division of licensed electrospace regions via secondary markets, providing rules for how regulatory limits change under aggregation or division. These flexible-use principles limit transmitter behaviors that tend to create a more difficult operating environment for receivers, while making receivers responsible for handling any remaining interference. The author shows how flexible-use principles could provide a basis for real-world flexible-use frequency bands.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.135-143
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• 1992

A novel sliding mode control with disturbance observer for position control of DC servo motor is presented. The conventional sliding mode controller changes the control structure depending on the state of switching surface and consequently, the control law is discontinuous and theoretically chatters at an infinite frequency. To overcome this problem in view of the practical implementation, the disturbance observer is used to compensate the effects of the parameter variations and the load disturvances. We can obtain the performance predetermined by the switching surface with continuous control law while the controlled system remains robust. The performance of the proposed controller with that of the conventional sliding mode controller through digital computer simulation and experiment.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.255-258
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• 2000

The supplementalγ controls of the FACTS are designed for the enhancement of the small signal stability in power system. The designed supplementary controllers using residue are applied to SVC or TCSC for the improving the damping ratio of dominant eigen value in the New England and 39 bus test system as the sample system. The results show the validation of the supplementary controller for the enhancement of the eigenvalues which have the low frequency oscillations with poor damping ratio as the unstable problem in the sample system.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2203-2204
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• 2006

When the coil with alternating current approaches to the conductor the eddy current flows in conductor. Eddy current is concentrated on the conductor surface and decrescent because of skin effet.. In this paper investigated eddy current characteristic that is happened in conductor. Analyzed characteristic using electromagnetic field finite element analysis program that is commercialized to analyze value of eddy current and penetration depth. Analyzed creation value of eddy current and penetration depth in conductor that change operation frequency and the material of conductor, coil outside diameter, inside diameter, position, type of conductor from analyzed eddy current characteristic. The results. using distribution of eddy current and penetration depth data is that will help to forecast ECT(Eddy Current Testing), Eddy current application and use field, eddy current loss.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.268-269
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• 2006

Auto-synchonizer is important device to match the voltage, frequency, phase of the generating system to those factors of the transmission line, when the synchronous generator is operated. There were few or no incidents by Synchronization failure at Hapcheon hydraulic power plant, since it was built in 1989. but incidents by Synchronization failure have often happend lately. From now, let's improve the efficiency on the maintenance of generating equipment by studying about the cause and the method for this problem by comparing with the set point of each device of synchronizing system.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.571-572
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• 2006

When the coil with alternating current approaches to the conductor the eddy current flows in conductor. Eddy current is concentrated on the conductor surface and decrescent because of skin effet.. In this paper investigated eddy current characteristic that is happened in conductor. Analyzed characteristic using electromagnetic field finite element analysis program that is commercialized to analyze value of eddy current and penetration depth. Analyzed creation value of eddy current and penetration depth in conductor that change operation frequency and the material of conductor, coil outside diameter, inside diameter, position, type of conductor from analyzed eddy current characteristic. The results, using distribution of eddy current and penetration depth data is that will help to forecast ECT(Eddy Current Testing), Eddy current application and use field, eddy current loss.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.145-146
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• 2012

Recently the problem of the fouling organisms, especially Sn-compounds is expanded to environmental problems from the chemical reaction with imposex and secondary contamination. One of the existing antifouling system, antifouling paints, is regulated from 2012, July because of seriousness about toxic substances such as TBT, mercury, copper and so on. TBT is known that causes a variety of biological inhibition in various chemicals even a very small amount of concentration. So it has been developed to replace it. In this paper, we try to develope a new system with the environmental background and the research of the adhesion characteristics of fouling organisms using a low current, high frequency high voltage pulse power, not toxic compounds.

• Journal of Fisheries and Marine Sciences Education
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• v.20 no.1
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• pp.12-22
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• 2008

This study presents the results of a delphi survey which is intended to identify technical skills that corporations expect of employees. A total of 300 managers from different businesses took part in the survey. To obtain the delphi data, a questionnaire of expected technical skills developed on the basis of previous research was used. The obtained data were analyzed in terms of frequency and other descriptive statistics. Eleven technical skills emerged as important ones in the corporate environment. In order of importance, subjects listed communication skills, business capabilities, negotiation skills, problem-solving ability, organizational adaptation, ability to gather and analyze relevant information, practical computer literacy, self-management, creativity, and foreign language proficiency.