• Progress in Superconductivity and Cryogenics
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• v.6 no.2
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• pp.25-28
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• 2004

Three-phase inductive superconducting fault current limiter (SFCL) with DC reactor rated on 6.6 $KV_{rms}/200 A_{rms}$ has been developed in Korea. This system consists of one DC reactor, AC/DC power converter, and a three-phase transformer, which is called magnetic core reactor (MCR). This paper deals with the short-circuit analysis of the SFCL. The DC reactor was the HTS solenoid coil whose inductance was 84mH. The power converter was performed as the dual-mode operation for dividing voltage between the rectifying devices. The short-term normal operation (1 see) and short-circuit tests (2∼3 cycles) of this SFCL were performed successfully. In regular short-circuit test, the fault current was limited as 30% of rated short-circuit current at 2 cycles after the fault. The experimental results have a very similar tendency to the simulation results. Using the technique for the fault detection and SCR firing control, the fault current limiting rate of the SFCL was improved. From this research, the parameters for design and manufacture of large-scale SFCL were obtained.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1515-1517
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• 2005

In this paper, we represent both occurrence reason of Surge-voltage and Leakage-current of AC drive system which is operated by Voltage-type PWM Inverter. It generates a compensating voltage which has the same amplitude as, but the opposite phase to, the common-mode voltage produced by the PWM inverter. The compensating voltage is superimposed on the inverter output by a common-mode transformer. As a result, the common-mode voltage applied to the load is canceled completely. The design method of the active common-mode noise canceler is also presented in detail. Therefore, we try to describe the method controling both of them and all of the proprieties are proved by our experiment.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.5
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• pp.44-51
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• 2008

UV lamp systems have been used for cleaning of display panels of TFT LCD or Plasma Display Panel (PDP). However, the needs for high efficient cleaning and low cost made high voltage plasma cleaning techniques to be developed and to be improved. Dielectric-Barrier Discharges (DBDs), also referred to as barrier discharges or silent discharges have been exclusively related to ozone generation for a long time. In this paper, a 6kW high voltage plasma power supply system was developed for LCD cleaning. The 3-phase input voltage is rectified and then inverter system is used to make a high frequency pulse train, which is rectified after passing through a high-power transformer. Finally, hi-directional high voltage pulse switching circuits are used to generate the high voltage plasma. Some experimental results showed the usefulness of atmospheric plasma for LCD panel cleaning.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.54-63
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• 2007

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage $380[V_{DC}]$ and a PWM inverter with LC filter to convent the DC voltage to single-phase $220[V_{AC}]$. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%]is obtained over the wide output voltage regulation ranges and load variations.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.909-915
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• 2010

In this paper, the unequal power divider based on CRLH (Composite Right/Left-Handed) transmission line with dual-band characteristic is proposed. They consist of dual-band branch line hybrid coupler, the connection between input and isolation port of hybrid coupler and ${\lambda}/4$ impedance transformer. When the transmission line between input and isolation port of hybrid coupler is asymmetrical connected, the divider is obtained the output results of the equal phase and unequal power dividing ratio. The simulation results of the divider represent the power ratio of 0 dB ~ 20 dB. To validate a function of divider, the hybrid coupler and transformer with 880 MHz and 1850 MHz is implemented. As a result, the proposed unequal divider obtains the power ratio of 3.2 dB ~ 8.8 dB at 880 MHz and 2.5 dB ~ 14.0 dB at 1850 MHz.

• Phonetics and Speech Sciences
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• v.13 no.3
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• pp.71-78
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• 2021

Most neural-network-based speech synthesis models utilize neural vocoders to convert mel-scaled spectrograms into high-quality, human-like voices. However, neural vocoders combined with mel-scaled spectrogram prediction models demand considerable computer memory and time during the training phase and are subject to slow inference speeds in an environment where GPU is not used. This problem does not arise in linear spectrogram prediction models, as they do not use neural vocoders, but these models suffer from low voice quality. As a solution, this paper proposes a Tacotron 2 and Transformer-based linear spectrogram prediction model that produces high-quality speech and does not use neural vocoders. Experiments suggest that this model can serve as the foundation of a high-quality text-to-speech model with fast inference speed.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.58-59
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• 2013

본 과제에서는 3.3kV/220V, 6kVA 용량의 양방향 지능형 반도체 변압기의 새로운 회로 구성을 제안하고 그 동작과 성능을 분석하였다. 제안하는 3상 반도체변압기는 1.9kV/127V 단상 반도체 변압기 모듈 3대를 Y-결선으로 구성하였으며, 각 단상 반도체 변압기는 고압 고주파 AC-DC 정류기와 저압 양방향 DC-DC-AC 컨버터로 구성되어 있다. 제안하는 3.3kV/220V, 6kVA 3상 반도체변압기를 제작하고 실험을 통해 그 동작과 성능을 검증하였다. 먼저 1차적으로는 3상 반도체변압기의 정상동작에 대해 실험을 실시하고 그 후에는 3상 입력전압에 외란이 발생하였을 때 보상성능을 순방향 조류와 역방향 조류 2가지 경우로 나누어 실험을 실시하고 그 결과를 분석하였다. 분석한 결과 제안하는 반도체변압기는 양방향 전력흐름이 가능하고 입력전압에 Sag가 발생한 경우에도 이를 보상하여 수전단이나 부하에 전력공급이 가능함을 알 수 있었다.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.71-73
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• 2006

본 논문은 단상 1MVA 22.9kV/220V 케이블 변압기의 설계, 제작 및 시험 결과를 서술한다. 케이블 변압기는 유입변압기의 폭발위험성과 환경오염 가능성이 없으므로, 인구밀집지역, 지하장소등 설치장소의 제한이 없는 장점이 있다. 제작된 케이블 변압기는 22.9kV급의 XLPE 케이블 전선을 사용하여 1차 권선을 제작하였으며, 2차측 권선은 내 단락시 특성이 우수한 몰드 권선 형태로 제작하였다. 사용된 XLPE 케이블은 도체-내부반도전층-XLPE-외부반도전층으로 구성되어 있으며, 외부반도전층은 접지된 구조이다. 철심은 단상 3각 구조로써 방향성 규소강판을 사용하였으며, 냉각방식은 공기 자연냉각방식이다. 제작된 변압기의 신뢰성을 확보하기 위하여, 특성시험과 절연시험을 실시하였다.

• Proceedings of the KIEE Conference
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• 2008.09a
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• pp.144-146
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• 2008

운전 중인 전력용 변압기의 고장 원인 중 진동에 의한 기계적 결함이 대부분을 차지하고 있다. 이러한 원인을 규명하기 위하여 한전 대전전력관리처 산하 변전소를 순회하면서 운전 중인 전력용 변압기에 대하여 진동 현상을 측정하였다. 측정 점은 변압기 한 면에 규칙 배열된 $5{\times}5$ 이다. 측정 점에 대한 진동 현상을 2D와 3D로 나타내어 분석하였다. 분석 결과와 전력용변압기의 경년, 설치 조건, 부하 정도에 따라 나타나는 현상을 분석하였다. 이 결과를 근거로 하여 전력용 변압기의 진동 기준을 정립하는데 기초로 활용하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.878-884
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• 2015

In this paper, Power Management System(PMS) simulator for Liquid Nature Gas Carrier(LNGC) is developed. Major components of power system for LNGC, such as generator, diesel engine and governor, transformer, circuit breaker, and 3 phase loads models are built based on MATLAB/SIMULINK. With these designed major parts, PMS simulator modeling is carried out. Based on MATLAB/Graphical User Interface, PMS simulator control for LNGC, and Human Machine Interface for monitoring is designed. PMS simulator for LNGC carries out simulation according to sequence of characteristics analysis. By comparing results of predicted simulation for each sequence to that of characteristics analysis, the reliability of PMS simulator for LNGC will be verified.