• 전기학회논문지
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• 제65권6호
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• pp.1007-1012
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• 2016

Induction motors are used widely in driving load of a fluid, such as a pump or a fan in the industry. Induction motor has been generated the voltage drop by the occurrence of a high current during startup. In addition, high start-up current can act as a mechanical stress on the shaft of the motor. So there is need a way to reduce the starting current. Soft start method is one of the many ways to reduce the starting current. This method uses silicon-controlled rectifiers(SCRs) for varying value of the voltage applied to the motor. There is a case for fixing or changing the thyristor firing angle to adjust the magnitude of the voltage. Starting power factor of induction motor is very low compared to the normal operation. Soft starting with the firing angle fixed needs to be considered a low power factor at startup. In this study, we compared the direct start characteristics and soft start characteristics considering the low power factor at the time of start-up. It was possible to confirm that the starting current and the voltage drop is present differently according to the firing angle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.350-352
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• 1995

The starting characteristics of single phase induction motor(SPIM) is described by control of phase and voltage. Auxiliary winding voltage is controlled by DC amplifier and phase is integrator. These processes enable comparison of torque with slip in each voltage and phase angle variations. Simulation and experimentation results of the motor's torque-slip characteristics using the controlled auxiliary winding voltage and phase angle arc shown and discussed. As a results, starting time is fast and main winding current is small when auxiliary winding voltage is low than rating voltage and starting characteristics is good in phase angle $90^{\circ}$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.817-820
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• 2002

Since a squirrel cage induction motor by NEMA Design types is designed to withstand full-voltage starting, direct starting method can be the most economical one. Starting a squirrel cage motor from standstill by connecting it directly across the line may allow inush currents of approximately 500-600% of rated current at lagging power factor of 35-50%. For many of the large motors, the starting inrush current may be great enough to cause voltage dips, which may adversely affect the building's lighting system. Electric utilities also have restrictions on starting currents, so that voltage fluctuations can be held to prescribed limits. Therefore the need for choosing the most appropriate method of motor starting is quite essential. In this paper, we proposed a plan for the selection of the most appropriate motor starting method, first by way of numeric simulation using manufacturer's data and second by way of actual experience. So far, more often than not, the selection of motor starting method has been accomplished only as regards to the capacity of the motor and the frequency of starting and stopping. But nowadays such high-tech apparatus as soft starters are being developed, and we are on the position to give more attention to clarify the way of selection of the motor starting method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 전기설비
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• pp.61-62
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• 2006

Since the starting reactor used for reducing inrush current of high voltage induction motor applies an electric current only when it is at the stage of transition, it gets lots of electrical or mechanical stress. In this aspect, the reliability on the starting reactor is very important because the reactor-relating-accident takes 80% of all the accident concerned with high voltage motor starting panel. In this study, we conducted an insulation test of starting reactor of high voltage induction motor of intake pumping station to the Seoul area And the result from this study was used as data for determining whether it's still usable or not.

• 한국산학기술학회논문지
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• 제8권4호
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• pp.748-757
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• 2007

본 논문은 대용량 유도전동기가 기동할 때 발생하는 큰 돌입전류로 인해 PCC(Point of Common Coupling)에 심한 전압 강하가 발생하게 되어 기동에 실패하는 문제를 해결하기 위해 대상 유도전동기의 기동 특성과 배전계통을 모델링하고 시뮬레이션을 수행함으로써 유도기 기동시에 전압저하 현상을 해석하였다. 문제가 되는 유도전동기는 2500KVA 용량의 펌프용 농형 유도전동기로 리액터 기동법을 채용하고 있다. 2500KVA 유도전동기 한대의 기동에는 문제가 없으나 기동 완료 후 PCC 전압이 다소 떨어진다. 하지만 추가로 동일 용량의 유도전동기가 기동하게 되면 PCC의 심한 전압강하로 기동에 실패하게 되는 문제가 발생하였다. 이러한 문제 해결을 위해 본 논문에서는 실제 기기의 기동시 토크-속도 곡선을 이용한 유도전동기의 기동 특성을 정확히 모델링하고 시뮬레이션을 수행하여 두 대의 대용량 유도전동기가 순차적으로 기동에 성공할 수 있는 적절한 전압보상 방안을 제안하였다. 본 논문에서 논의되는 대용량 유도전동기는 한국수자원공사의 취수장에서 운전되고 있으며 대상 유도전동기 및 배전계통은 PSCAD/EMTDC 소프트웨어를 사용하여 모델링 및 시뮬레이션을 수행하였다.

• 전기학회논문지P
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• 제53권3호
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• pp.148-151
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• 2004

For turn on high pressure sodium vapor lamp, Starting Voltage is very important factor. This starting voltage supply to high pressure sodium vapor lamp as electric discharge lamp, Electric field is producted in electric discharge tube, So accelerative electron collide against vapor atom and second electron is generated, And rapidly the current flow to electric discharge tube. This starting voltage is high voltage and source for melting contact that relay is according as turn on/off high pressure sodium vapor lamp. Consequently, This paper propose that the prevention of melting contact in accordance relay of controller for turn on/off high pressure sodium vapor lamp.

• 전기학회논문지P
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• 제57권3호
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• pp.225-230
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• 2008

Reactor starting method has the advantage of simplicity and closed transition in spite of lower starting torque per kVA. This method allows a smooth start with almost no observable disturbance on transition and is suitable for applications such as centrifugal pumps or fans. Reactive power doesn't contribute to work but needs to sustain the electromagnetic field required for the induction motor to operate. Starting power factor of induction motor is specially lower than running power factor. Power factor application is needed to compensate for the lower power factor of induction motor. This power factor compensation systems is occasionally being hit by the effects of the starting reactor connection position at the starting, stopping of high-voltage induction motor. This paper describes voltage and current stress affected by the installation position of power factor compensation application at the reactor starting method.

• 전기학회논문지P
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• 제64권2호
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• pp.62-66
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• 2015

Induction generator is easy to durability and maintenance than the synchronous generator. So, recently Induction generator has been widely applied to small-scale hydroelectric power plant. When the rotor is operating faster than synchronous speed, induction machine can generate electric power. Induction generator has a large inrush currents, such as the starting current of the induction motor. Induction motor has been designed a variety of rotor shape in order to reduce starting current. Since the occurrence of high inrush current cause a voltage drop to the system, it will need to reduce possible. Because the starting current of the squirrel-cage induction motor varies in accordance with the rotor shape, it is necessary to analyze the magnitude of inrush current in order to apply to the generator. In this study, we analyzed the inrush current and the voltage drop caused in accordance with the rotor shape of 1500kw induction generator.

• 대한전기학회논문지:전력기술부문A
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• 제53권11호
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• pp.589-595
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• 2004

This paper presents a modeling and simulation of a grid-connected wind turbine generation system with respect to wind variations, starting of large induction motor and three-phase fault in the system, and investigates voltage variations of the system for disturbances. It describes the modeling of the wind turbine system including the drive train model, induction generator model, and grid-interface model on MATLAB/Simulink. The simulation results show the variation of the generator torque, the generator rotor speed, the pitch angle, terminal voltage, system voltage, fault current, and real/reactive power output, etc. Case studies demonstrate that the pitch angle control is carried out to achieve maximum power extraction for wind speed variations, starting of a large induction motor causes a voltage sag due to a large starting current, and a fault on the system influences on the output of the wind turbine generator.

• 전기의세계
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• 제31권3호
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• pp.197-203
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• 1982

The effects on the characteristics of 20-W fluorescent lamp were studied when applying magnetic field to its positive column. First, when the direction of the magnetic field is axial, i.e., along the lamp, if the magnitude of the field is stronger than the critical field, lamp voltage is increased, lamp current decreased, luminous flux increased, starting voltage decreased, as increasing the applied magnetic field. At the magnetic flux density is 130 gauss, luminous flux is increased to about 6 percents and starting voltage is increased to about 45 percents. Second, when the direction of the magnetic field is transverse to the lamp axis, as increasing the applied magnetic field, lamp voltage is increased, lamp current decreased, luminous flux increased and starting voltage is nearly constant, but the rates of increase or decrease of this case is different from those of the first. At the magnetic flux density is 300 gauss, luminous flux is increased about 45 percents. In both cases, electric power dissipated by lamps is the same as that of the lamp which magnetic field is not applied to.