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유도발전기 직입 기동에 적합한 변압기의 용량 산정에 관한 연구
박영진(Young-Jeen Park),김종겸(Jong-Gyeum Kim) 한국조명·전기설비학회 2021 조명·전기설비학회논문지 Vol.35 No.3
Induction generators have the advantages of simple structure, low cost, and easy maintenance, like induction motors. So, Induction generators are often used in small hydro power plants where the output of the generator is not high. The induction generator has a drawback that it causes a voltage drop due to a high inrush current when the induction generator is directly inserted and is connected to the system like the start of the induction motor. When a voltage drop occurs in the same bus line, it may affect the devices connected in parallel and prevent them from operating, or cause a malfunction. In order to reduce the influence of the starting current of the induction motor or the inrush current of the induction generator, a number of studies have been proposed that have proposed various starting methods. The current reduction method for reducing the voltage drop is the addition of another starting system for the induction motor and induction generator. In this study, using the method applied for calculating the capacity of the emergency generator, the capacity of the transformer connected to the system after the direct starting of the induction generator was calculated considering the magnitude of the voltage drop. As a result of analysis, it was confirmed that the voltage drop on the primary side of the transformer was very low, but the secondary side of the transformer had a large difference in the voltage fluctuation rate depending on the transformer capacity.
하이브리드 PWM에 의한 인버터 가변속 운전시의 패턴절환기법
서영민(Young-Min Seo),박영진(Young-Jeen Park),홍순찬(Soon-Chan Hong) 전력전자학회 1998 전력전자학술대회 논문집 Vol.- No.-
This paper proposes the hybrid PWM scheme that can obtain less harmonic characteristics in GTO inverters. By employing the variable of the dc-link voltage Vdc, the hybrid PWM pattern can ideally compensate the dc input fluctuation together with selected harmonics elimination. The transient behavior, which the magnetic flux and torque are altered and the large current flows instantly, may be produced when the mode change. To reduce such an undesirable transient behavior, it is also presented the technique for the gear changing of inverter operated with the hybrid PWM. The results are verified by simulations and experiments
3상 4선식에시 비선형 부하의 운전시 유도전동기의 특성 해석
김종겸,박영진,이은웅,Kim, Jong-Gyeum,Park, Young-Jeen,Lee, Eun-Woong 한국조명전기설비학회 2006 조명·전기설비학회논문지 Vol.20 No.8
3상 4선식 전원공급 시스템에서 단상 및 3상 부하의 운전하에서 전압 불평형은 부하의 불평형 운전에 의해 발생되고, 전류 불평형은 떨어진 전압 품질에 의해 더욱 심해진다. 에너지 변환장치로 사용되는 여러 형태의 컨버터는 3상 4선식 배전시스템에 직접적으로 고조파 전류를 주입함으로서 고조파 왜란을 증가시킨다. 고조파 전류는 전동기 출력 토크를 감소시키고, 전동기를 과열 또는 소음을 증가시키며 회전자에 토크 맥동을 증가하여 기계적인 공진과 진동을 발생하는 등 여러 가지 부작용을 낳고 있다. 따라서 본 논문은 3상 4선식 배전시스템에서 선형 및 비선형 부하의 혼합 운전시 불평형과 고조파 성분에 의해 유도전동기의 특성 변화에 대한 연구로서 선형 단독운전, 비선형 부하 결합에 따른 특성 변화를 해석한 것으로서 단상 비선형 부하의 추가 운전시 5 고조파 필터로도 저감이 어려운 고조파로 인해 토크 맥동 횟수는 줄고 리플값은 증가함을 확인할 수 있었다. Voltage unbalance will be generated by the load unbalance operation such as combination operation of single & three phase load and current unbalance will be more severe by the deteriorated voltage quality. Under the these unbalance conditions, all power electronic converters used in different types of electronic systems can increase harmonic disturbances by injecting harmonic currents directly into the feeder grid of three phase 4-wire. Harmonic current may cause torque to decrease. it may also overheat or become noisy and torque oscillation in the rotor can lead to mechanical resonance and vibration. This paper presents a scheme on the characteristics of induction motor under the combination of linear & non-linear loads at the three phase 4-wire power distribution system by the unbalance and harmonic components. It was able to confirm that the number of torque pulsation decreased and torque ripple values increased by the harmonics that reduction was difficult by five harmonics filters at additional driving time of single-phase non-linear load.