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장수진,류동균,원충연,이진국,배기훈,김수석 성균관대학교 2003 학술회의지원논문목록집 Vol.2003 No.-
A synchronous generator is equipped with an automatic voltage regulator(AVR), which is responsible for keeping the output voltage constant under normal operating conditions at various levels. The output voltage of Synchronous Generator is regulated constantly by field voltage control in excitation system. High frequency PWM converter (Buck converter) type excitation system for synchronous generator that can sustain proper output voltage level even at the fault condition happened. The proper operation of the proposed excitation system was verified through the simulations and the experiments.
능동 클램프 ZVS 플라이백 컨버터의 역률개선에 관한 연구
최태영,류동균,이우석,안정준,원충연,김수석 성균관대학교 2002 학술회의지원논문목록집 Vol.2002 No.-
본 논문에서는 single-stage, two-stage 두가지 역률보상(PFC)기법을 기존의 능동 클램프 플라이백 컨버터에 적용하여 역률 개선을 하였다. 삽입된 플라이백 컨버터의 능동클램프회로가 주스위치와 보조스위치의 영전압스위칭(ZVS)을 구현하며, 스위칭 손실을 줄임으로써 고효율을 얻을 수 있고, 높은 주파수에서의 스위칭이 가능하다. 하지만 일반적으로 사용되는 다이오드정류기, 평활용커패시터에 의한 낮은 역률의 문제점이 남아있다. 본 논문에서는 300W급 능동 클램프ZVS플라이백 컨버터를 설계하여 single-stage, two-stage방식을 적용, 입력역률개선을 시뮬레이션과 실험에 의해 입증하고자 한다. This paper analyzed PFC of active clamp ZVS flyback converter by adding two method PFC (Power Factor Correction) circuit - two-stage and single-stage. The addition of active clamp circuit also provide a mechanism for achieving ZVS of both the primary and auxiliary switches. ZVS also limits the turn off di/dt of the output rectifier, reducing rectifier switching loss and switching noise, due to diode reverse recovery. As a results, the proposed converters have characteristics of the reduced switching noise and high efficiency in comparison to conventional flyback converter. The simulation and experimental results show that the proposed converters improve the input PF of 300W ZVS flyback converter by adding single-stage, two-stage PFC circuit.
유아교육과 학사학위 전공심화과정 등록 및 수업 운영 현황 분석
김수연 ( Soo Yeon Kim ),윤길근 ( Kilg Yuen Yoon ),이희경 ( Heek Yung Lee ),김성수 ( Sung Soo Kim ) 영유아교육학회 2009 영유아교육연구 Vol.12 No.-
이 연구는 유아교육과 학사학위 전공심화과정의 등록 및 수업운영 현황을 조사하고 문제의 원인을 분석함으로써, 전공심화과정 제도가 발전하기 위한 과제를 제시하고자 한다. 이 연구는 학사학위 전공심화과정 개설 19개 대학 학과장을 대상으로 질문지조사, 유아교육과 교수 및 전문대학정책관련 전문가 등 7명 대상으로 면접 조사를 실시하였다. 2009년 현재 유아교육과 학사학위 전공심화과정은 19개 전문대학 20개 과정이 운영되고 있으며, 등록률은 53.3%(272/510명), 졸업률은 96.9%이다 면접 결과, 교수들은 전공심화 과정의 개설 당위성과 제도적 한계로 인해 모집 및 교육과정 운영의 어려움 등 현실적 업무 속에서 많은 갈등을 하고 있는 것으로 나타났다. 연구결과, 산업체 경력기간에 대한 폐지 또는 축소 등 제도의 합리적 개선, 수요자 분석에 기초한 과정 개설, 교육현장 및 수요자의 요구를 반영한 실무중심 현장 중심 직업교육과정 운영 등의 발전적 과제를 제안한다. This study examined the present situation of the enrollment management and presented causes and solutions of problems by analyzing the perception of professors and experts on Bachelor`s Degree Course at Department of Early Childhood Education at Junior Colleges. At present, 19 Junior Colleges manage 20 Bachelor`s Degree Course at Department of Early Childhood Education. Their enrollment ratio is 53.3%(272/510persons) and their completion ratio is 96.9%. The occupation distribution is 36 principals(18.8%), 147 teachers(77.0%). Results of Interviews indicated that professors had the conflicts and difficulties in collecting students and management of this course. Even though they know well this course is indispensability for the development of department and college which they worked at, they had difficulties in collecting students causing by systematic limits. As the results of research, this study suggested an abolition or reduction of one-year work experiences in the industries and the management of in-service training course reflecting the needs of users and education fields.
김경수,최정영,김준기,조상욱,여향순,강명원,신성하,고영춘,임연근 대한소화기내시경학회 2001 Clinical Endoscopy Vol.22 No.1
Multiple carcinoid tumors in stomach are very rare tumors and associated with pernicious anemia, chronic atrophic gastritis and Zollinger-Ellison syndrome. These are believed to be due to hypergastrinemia, resulting in chronic stimulation of enterochromaffine-like (ECL) cells, leading to hyperplasia, metaplasia and ultimately neoplasia. The carcinoid tumor is potentially malignant, even though it may grow slowly, so the treatment of choice must be endoscopic lumpectomy or surgical gastrectomy. The prognosis depends on the site of the tumor and its size. Most carcinoid tumors are less than 1 cm in size and metastasis is uncommon but metastasis in tumors with size over 2 cm is common. A case of multiple carcinoid tumors in stomach, which was successfully removed by endoscopy, is herein reported.
The development of LF power supply for dry scrubber
Soo-Seok Kim,Chung-Yuen Won,Dae-Kyu Choi,Sang-Don Choi 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10
In this paper, the development of the LF power supply for dry scrubber is discussed. 1500kW, 100kHz LF power supply is designed and tested. The main power stage is used for the FB PWM inverter with an LC filter in the secondary circuit. The operation characteristics of LF power supply are verified by simulation and experimental results.<br/>
Soo-Cheol Shin,Hee-Jun Lee,Young-Ho Kim,Jung-Hyo Lee,Taeck Kie Lee,Chung-Yuen Won 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.5
In general, for a large power system like DC distribution system for buildings, several power converters are modularized for parallel operation. However, in parallel operation, inconsistency of parameters in each module causes circulating current in the whole system. Circulating current is directly related to loss, and, therefore, it is most important for the safety of the power system to supply the suitable current to each module. This paper proposes a control method to reduce circulating current caused during parallel operation. Accordingly, the validity of parallel operation system including response characteristics and normal state was verified by simulation and experiment result.
김수석(Soo-Seok Kim),최대규(Dae-Kyu Choi),최상돈(Sang-Don Choi),원충연(Chung-Yuen Won) 전력전자학회 2001 전력전자학술대회 논문집 Vol.2001 No.7
In this paper, the development of the LF power supply for dry scrubber is discussed. 1500kW, 100kHz LF power supply is designed and tested.<br/> The main power stage is used for the FB PWM inverter with an LC filter in the secondary circuit. The operation characteristics of LF power supply are verified by simulation and experimental results.
Walsh-Fourier변환을 사용한 PWM인버어터의 새로운 고조파 제거방법에 관한 연구
安斗守,元忠淵,李海基,金泰勳 成均館大學校 科學技術硏究所 1989 論文集 Vol.40 No.2
The thesis presents the problem of new harmonic elimination method of P\V\i inverter f d induction motor system using walsh series. In other words, this thesis presented technique of the selective harmonics elimination (SHE) by W-FT series in three phase PWM inverter output waveform. A microprocessor(8086 CPC)-controlled three phase induction motor system in order to verify this algorithm is presented. It is designed for a three output voltage in the 1∼60Hz inverter with the 5th and 7th harmonics, 5th, 7th, 11th, and 13th harmonics eliminated, and with the fundamental wave amplitude proportional to the output frequency. As the results, the performance of the proposed method could eliminate the harmonics and reduce computation time which determines switching pattern. In inverters, dead time circuits are inserted in the switching signals to prevent the dc link shortage. This causes the "dead-time effect", the fundamental voltage drop and the generation of low order harmonics, this thesis is deals with quantative prediction of dead-time effect and its compensation in PWM inverters. The performance of the compensation circuits is conformed through the sir,.-elation and the experiment. In the future, the proposed PWM pattern by W-FT series, is effective not only to the induction but also to the other electromagnetic machine such as volta e regulator, UPS.