• 전력전자학회논문지
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• 제24권4호
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• pp.273-278
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• 2019

This study proposes a method for improving the overmodulation performance of a three-phase inverter to obtain an enhanced output torque for the AC motors. In the inverter-fed AC motor drives, the output torque of the motor can be enhanced by utilizing the overmodulation region as well as the linear modulation regions of the inverter. The overmodulation method is used for this overmodulation operation of the inverter. However, the voltage gain, the ratio of the output voltage of the inverter to the reference voltage achieved by the conventional overmodulation methods becomes nonlinearly smaller than unity. Therefore, the effect of improving the output torque of the AC motors is insignificant even when the overmodulation region is utilized. In this study, we propose a method that improves the overmodulation performance of the inverter by compensating the limited amount of the reference voltage in the overmodulation operation to enhance the output torque of the AC motors. The effectiveness of the proposed method is verified through the simulations and experiments with an 800 W permanent magnet synchronous motor.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.221-224
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• 1998

A PWM inverter with an induction motor often has a problem with a high-frequency leakage current that flows through the distributed electrostatic capacitance from the motor windings to ground. This paper presents an equivalent circuit for high-frequency leakage currents in PWM inverter feeding an induction motor, which forms an LCR series resonant circuit.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권11호
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• pp.646-654
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• 1999

This paper deals with PWM patterns for harmonic reduction in inverter fed traction motors and the gear changing techniques for the variable speed drive of traction motor. GTOs are used as switching device of inverter because traction motor is a large load. To derive PWM rattern which can minimize the harmonics with the limited switching frequency, the output current and torque characteristic of SPWM and SHE PWM was analyzed. GTO inverter used for traction motor drive includes harmonics in the output current and torque by the limitation of switching frequency. However, the hybrid PWM method that adopt SPWM in the range of low frequency and SHE PWM in upper frequency range can achieve less harmonic characteristics in GTO inverters. If the traction motor is driven in variable speed by the proposed PWM pattern, 7 times of gear changing is needed. At the instant of the mode change, magnetic flux and torque may be altered and the large current flow. To reduce such an undesirable transient behavior, it is also presented the technique for the gear changing of inverter fed traction motor drive operated with the hybrid PWM. The results are verified by simulations and experiments.

• 조명전기설비학회논문지
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• 제22권10호
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• pp.111-117
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• 2008

일반적으로 산업현장에서 널리 사용되는 유도전동기는 상용인버터를 이용하여 속도제어를 하게 된다. 상용인버터로 구동되는 유도전동기는 인버터의 고속 스위칭에 의한 마이크로 서지전압을 발생한다. 이러한 마이크로 서지는 전동기의 소손뿐 만아니라 PLC 제어계통에 있어서 노이즈 문제를 발생하며, 생산 활동에 막대한 지장을 초래하게 된다. 본 논문에서는 마이크로 서지의 발생 메커니즘을 살펴본 후 전동기 소손 방지를 위한 대책을 제시하고 인버터 출력단에 LCR 필터를 부착하여 실험하였으며 결과로 마이크로 서지전압이 저감됨을 확인하였다 또한 PLC 제어계통의 노이즈 억제에 대해 이론적 고찰을 통해 대책도 제시하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권4호
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• pp.538-550
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• 1998

The variable frequency and variable voltage AC source made by a conventional inverter which is composed of power semi-conductors includes much noises in sine wave due to high frequency switching of DC source. In this paper the 3rd low pass LC filter for a variable speed 3 phase induction motor driven by a full bridge inverter is introduced to solve the EMI problem by serious noise current. The utility of a modified 3rd order Butterworth LC filter is confirmed through FFT analysis of sine waves and noiseless ACsource can be obtained by the proposed LC filter. The speed of a 3 phase induction motor driven by a full bridge inverter with a LC filter is satisfactorily controlled by a digital PID controller under the condition of stepwise load and setpoint changes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.746-748
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• 1987

A volocity and an efficiency of an induction motor are lower than those of a DC motor. But in the control, the utility of an AC motor is more enlarged with the development of inverter. But unfortunately, in using the induction motor, it include a lot of harmonics because of switching of semi-conductor devices(SCR or Tr) in the inverter. In PCR, as the change of a firing angle $\alpha$, harmonics are changed. Hence, in this thesis analyze the harmonics and provide the region of it's application when PWM and 6-step applied to inverter. Of course, frequencies of inverter changed. Especially, in PWM a carrier ratio is changed.

• 전기학회논문지
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• 제58권5호
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• pp.976-981
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• 2009

This paper proposed optimal design and microcontroller driver for driving the thin-type ultrasonic motor. To find the optimal size of the stator, motions of the motor were simulated using ATILA by changing length, width and thickness of the ceramics. Two sinusoidal waves which have 90 degree phase difference were needed for driving the thin-type motor. The thin-type ultrasonic motor driver was composed of microcontroller(Atmega128), push-pull inverter, encoder and AD-converter. Microcontroller generates four square waves which have variable frequency and 25[%] duty ratio in $20{\sim}150$[kHz]. The output signals of microcontroller were converted to sine wave and cosine wave by push-pull inverter and were applied to the thin-type ultrasonic motor. The encoder and AD-converter were used for maintaining speed of the thin-type ultrasonic motor. The AD-converter controlled DC voltage of inverter in accordance with output signal of encoder. Using the driver, characteristics of the motor as speed and torque were measured.

• 융합신호처리학회논문지
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• 제3권3호
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• pp.76-81
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• 2002

대전력 전동기 구동장시스템에서 하드 스위칭 토폴로지는 심각한 스위칭 손실과 EMI잡음문제를 일으키며, 인버터 스위칭 주파수는 과도한 손실과 열적문제 때문에 제한되게 된다. 본 연구의 목적은 개선된 소프트 스위칭 토폴로지에 의해 스위칭손실과 EMI를 저감할 수 있는 대용량 교류전동기의 구동에 적합한 시스템을 개발하고자하며, 시뮬레이션과 실험을 통하여 그 타당성을 입증하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제17권3호
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• pp.70-79
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• 1993

The application of A.C. motor to servo system is rapidly increased according to the recent advance of power electronics and digital control techniques. The induction motor which has a simple structure and needs less maintenance is used in the industrial field for the variable speed and position control recently. In this paper, the current characteristic of the full-bridge resonant inverter is studied by comparing with the computer simulation and the laboratory experiment when the ratio of forced frequency to the natural frequency and the ratio of conduction time to the period at the given frequency is changed. And then, the full-bridge resonant inverter is applied to the speed control of single phase induction motor.

• Journal of Power Electronics
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• 제7권4호
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• pp.271-277
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• 2007

In this paper, an induction motor rotor fault diagnosis system using current signals, which are measured using the axis-transformation method is presented. Inverter-fed motor drives, unlike line-driven motor drives, have stator currents which are rich in harmonics and therefore fault diagnosis using stator current is not trivial. The current signals for rotor fault diagnosis need precise and high resolution information, which means the diagnosis system demands additional hardware such as a low pass filter, high resolution ADC, an encoder and additional hardware. Therefore, the proposed axis-transformation method is expected to contribute to a low cost fault diagnosis system in inverter-fed motor drives without the need for any additional hardware. In order to confirm the validity of the developed algorithms, various experiments for rotor faults are tested and the line current spectrum of each faulty situation, using the Park transformation, is compared with the results obtained from the FFT(Fast Fourier Transform).