• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.414-417
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• 1999

According to development of power electric technology from industrial field to electronic home appliances, recent SMPS using semiconductor is spread widely. Electric converting instrument uses a sine wave voltage source, namely an usual power source, and it gets a non-sines power source from power source because current flows through one part in waveform of one cycle. This injects higher harmonic source in source part, absorb pollution source. And this cause quality deterioration, durability shortage of electric power instrument, spreading accident of electric solver system, and so on. It can't supply an electric source of good quality in industry, so become an impedimental element in improving productivity and reliance. This study can be used in prediction of hindrance and diagnosis material and intends to suggest a countermeasure about measurement data.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.3
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• pp.313-320
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• 2013

The fractional slot windings are widely used in rotating machine in order to increase the flexibility of design and improve the voltage waveform. However, the MMF wave of fractional-slot windings are found to contain unique harmonic component, which are designated as even order space flux harmonics, fractional number flux harmonics, or both. They may cause stray loss and stator core vibration. This paper proposes new winding methods "novel interspersed windings" and "expanded group windings" to reduce these harmonics. The advantages of two proposed windings are verified by using numerical analysis and measurement test of winding model.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.715-728
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• 1997

The aim of this paper is to investigate the secondary buckling behaviour and mode-coupling of spherical caps under uniformly external pressure. The analysis makes use of a rotational finite shell element on the basis of strain-displacement relations according to Koiter's shell theory (Small Finite Deflections). The post-buckling behaviours after a bifurcation point are analyzed precisely by considering multi-mode coupling between several higher order harmonic wave numbers: and on the way of post-buckling path the positive definiteness of incremental stiffness matrix of uncoupled modes is examined step by step. The secondary buckling point that has zero eigen-value of incremental stiffness matrix and the corresponding secondary mode are obtained, moreover, the secondary post-buckling path is traced.

• KIEE International Transactions on Power Engineering
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• v.12A no.1
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• pp.26-30
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• 2002

The four fuzzy criteria to distinguish the internal fault from the inrush fur the power transformer protection have been identified. They are based on the wave shape, terminal voltage, fundamental and second harmonic component of differential current. systematic way to determine the associated fuzzy membership function is also proposed.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.7
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• pp.668-679
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• 1990

The fully digitalized inveter has some difficulties in implementation because of the limitation of available memory capacity and computation time. This paper describes a new PWM(Pulse Width Modulation) Inverter technique which linearizes switching angle characteristics of SHEPWM(Selected Harmonic Eliminatin Pulse Width Modulation) Inverter. Also the detailed description of the scheme along with the realization is presented. The simulation and experimental results show that the proposed schemes have the advantates such as good voltage waveforms and memory-saving.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.403-406
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• 2003

For small capacity rectifier circuits such as these for consumer electronics and appliances, capacitor input type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been presented previously. However, most of these employ switching devices, such as FET and the like. The absence of switching devices mattes systems more tolerant to over-load and brings low radio noise benefits. We propose a power factor correction scheme using a LC resonant in commercial frequency without switching devices. In this method It makes a sinusoidal wave by widening conduction period using the current resonance in commercial frequency, Hence, the harmonic characteristics can be significantly improved, where the lower order harmonics, such as the fifth and seventh orders are much reduced The result are confirmed by the theoretical and experimental implementations.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.524-525
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• 2014

In this paper, we propose algorithm plan variable for detection of DC arc. Changes of surrounding frequencies of harmonic wave is proposed to detect DC arc. To prove validity of these variables, we analyzed frequency based on the measured data and waveform of load current by performing the experiment which generates DC arc by using DC arc generator regulated in UL1699 was carried out.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.121-124
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• 1998

Front end AC to DC converters of the boost type are used in traction applications for generating the DC link for the inverters. A GTO based converter is usually switched with a switching frequency of 300 to 500Hz, resulting in low frequency harmonic problems. In order to avoid this, multiple converters with Phase shifted carrier waveforms are used to suppress the low frequency harmonics. A detailed study of an AC to DC converter, with two converters parallely operated with Phase shifted carrier wave farms is Presented in this paper.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.174-176
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• 1995

An additional consideration for using general Induction Motor are about copper loss by harmonic component of source, and increase of iron loss due to switching frequency in semiconductor devices, so that these losses come to be significant elements on design for motors used for variable V/F. In this paper, therefore, the effects of the losses are discussed, in the case the source is generated by square wave and PWM Inverter.

• Bulletin of the Korean Chemical Society
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• v.17 no.7
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• pp.607-612
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• 1996

A series of new NLO-active poly(4-nitrophenylallylamine) derivatives was synthesized by the nucleophilic substitution reaction of several substituted 4-nitrohalobenzenes and poly(allylamine hydrochloride). All polymers obtained were amorphous and their glass transition temperatures (Tg) were observed around 148-160 ℃. For each of these polymers, their specific Tg values were dependent on characteristic electronic structures. UV-visible absorption spectra showed maximum absorption intensity at 355-393 nm for π-π* transition of alkylaminonitrophenyl groups. The χ(2)value of poly(4-nitrophenylallylamine), as determined by the second harmonic generation at 1064 nm, for a thin polymer film poled at an elevated temperature, was 1.4x10-8esu. The third-order NLO properties of poly(4-nitrophenylallylamine) derivatives were evaluated through measurement of degenerate four-wave mixing technique and χ(3) coefficient in the range of 2.7~3.2x10-12 esu at 602 nm was found with 400 fs laser pulses.