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변압기 임피던스 차이에 따른 유도발전기 기동시 전류와 전압강하에 관한 연구
김종겸 대한전기학회 2022 전기학회논문지 Vol.71 No.5
Like an induction motor, an induction generator has the disadvantage that the voltage drop occurs due to a high starting current during the motoring mode before it is connected to the grid. The voltage drop due to such a high starting current can greatly affect the operation of other devices connected to the trunk line. For stable operation of the device, it is very important to keep the voltage drop within the allowable range. Transformers have different percent impedance depending on their capacity. In general, when the transformer capacity is low, the percent impedance is low, and vice versa, the percent impedance is high. The value of the transformer's percent impedance can greatly affect the voltage drop. This study analyzed how the voltage drop caused by the starting current changes according to the difference in the percent impedance of the transformer when the induction generator is in the motoring mode area before starting and operating as a generator.
출력 변동에 따른 유도발전기의 역률 보상기법에 관한 연구
김종겸 대한전기학회 2022 전기학회논문지 Vol.71 No.6
Induction generator are widely used in small-scale or micro-scale plants. Induction generators are sometimes operated at rated output, but in most cases, they are operated lower than rated output. Induction generators have an inductive load and a power factor of about 0.8 during rated operation, but the power factor drops below this when operating below the rating. A capacitor is attached to the generator terminal to compensate for the low power factor, but the capacity of this capacitor is calculated under the conditions of rated operation of the induction generator and is not suitable for output change. When the output of the generator changes, the current flowing through the stator of induction generator changes, but the excitation current required for magnetization changes very little. When the reactive power required for magnetization of the induction generator is compensated for on behalf of the power source, the power factor can be operated close to 1 even when the torque of the generator changes. In this paper, a control algorithm that can keep the power factor constant even when the output of the generator changes by installing a STATCOM(Static Synchronous Compensator) between the power supply side and the generator side is presented, and the possibility is presented through analysis.
유도전동기 기동시 전압강하와 변압기 용량 및 임피던스에 관한 연구
김종겸 대한전기학회 2022 전기학회논문지 Vol.71 No.4
Induction motors have the disadvantage of generating a voltage drop due to a high current during startup. This voltage drop may have a bad effect on other loads, so the voltage drop must be reduced within a certain range. The improvement of the starting method is also important to reduce the voltage drop, but the contents of the transformer's capacity and percent impedance are also very important. Transformers have different percent impedance depending on their capacity and voltage. The percent impedance is also related to the voltage drop. The higher the capacity of the transformer, the higher the percent impedance, and the lower the capacity, the lower the percent impedance. In this study, in order to limit the voltage drop to within the allowable range when starting the induction motor directly, the transformer capacity was calculated by considering the percent impedance together.
1선 지락 사고시 배전선로 접지저항에 따른 유도전동기 토크 특성 변화에 관한 연구
김종겸 대한전기학회 2022 전기학회논문지 Vol.71 No.10
Customers should be provided with good quality of electricity for stable load operation. Various failures can occur from substations and distribution lines to consumers. The most common failure in distribution lines is single-line ground fault. For distribution lines, grounding resistance is stipulated according to the length of the line and installation conditions. When single-line ground fault occurs, the magnitudes and phase angles of voltage and current change asymmetrically, resulting in unbalance. Three-phase induction motors among customer facilities are greatly affected by these voltage and current imbalances. Imbalance of current and voltage caused by a fault can have a great effect on the torque of the motor. In this study, we analyzed how the pulsating torque of an induction motor appears according to the ground resistance of the line during single-line ground fault in a distribution line. It was confirmed that the higher the ground resistance of the distribution line, the lower the amplitude of the pulsating torque.
김종겸,이동주 대한전기학회 2022 전기학회논문지 Vol.71 No.5
Induction motors are one of the most commonly used inductive loads in industrial settings. Induction motors may be operated at rated operation, but they are often operated at lower ratings. Induction motors have an inductive load and a power factor of about 0.8 during rated operation, but the power factor drops below this when operating below the rating. A capacitor is attached to the motor terminal to compensate for the low power factor, but the capacity of this capacitor is calculated under the conditions of rated operation of the induction motor and is not suitable for load fluctuations. When the load changes, the current flowing through the stator of induction motor changes, but the excitation current required for magnetization changes very little. When the reactive power required for magnetization of an induction motor is compensated for on behalf of the power source, the power factor can be operated close to 1 even when the motor torque changes. In this paper, by installing a static synchronous compensator(STATCOM) between the power source and the induction motor side, the reactive power required for magnetization is supplied to the induction motor instead of the power source even when the induction motor torque changes. A control method was presented, and the possibility was analyzed through simulation.
김종겸 한국조명.전기설비학회 2023 조명·전기설비학회논문지 Vol.37 No.4
Induction motor are most often used for driving rotating machines in industrial fields. This induction motor is a typical inductive load and is a rotating machine with a characteristic that the power factor varies according to the rotational speed. This induction motor contains two reactive power components. The first is the reactive power of the magnetization component used to create the rotating magnetic field, and the other is the reactive power corresponding to the formation of the leakage magnetic flux. Induction motors have different magnitudes of reactive power from starting to operating at rated speed. Therefore, the power factor also varies accordingly. In this study, we analyzed the effect of the reactive power on the power factor by comparing the magnitude of the magnetization component and the leakage component with the change of the rotation speed.