• 전력전자학회논문지
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• 제6권2호
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• pp.191-201
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• 2001

현재 산업용, 가정용 전동기의 수요는 급증하고 있다. 이는 스위칭 소자와 제어기술의 현저한 진보가 있었기 때문이며 이중 BLDC 전동기의 사용이 증가하고 있다. 그러나 일반적으로 사용되고 있는 3상 BLDC 전동기 맥동토크가 크고 속도변화에 민감하며 높은 속도에 적용하는데 한계가 있다. 이러한 문제를 해결하기 위해서는 전동기의 상과 극수, 슬롯수를 증가시켜야만 한다. 그래서 현재 다상 BLDC 전동기의 연구가 진행중에 있다. 하지만 다상 BLDC에서는 높은 스위칭 주파수로 인해서 일반적으로 쓰고 있는 히스테리시스 전류제어기를 제안하였고 7상 BLDC 전동기에 적용하여 시뮬레이션과 실험을 통해서 타당성을 입증하였다.

• Journal of Power Electronics
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• 제7권3호
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• pp.222-232
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• 2007

This paper presents the application of a single phase AC-to-DC converter using a three-phase series parallel (SPRC) resonant converter to variable speed dc-drive. The improved power quality converter gives the input power factor unity over a wide speed range, reduces the total harmonic distortion (THD) of ac input supply current, and makes very low ripples in the armature current and voltage waveform. This soft-switching converter not only possesses the advantages of achieving high switching frequencies with practically zero switching losses but also provides full ranges of voltage conversion and load variation. The proposed drive system is the most appropriate solution to preserve the present separately excited de motors in industry compared with the use of variable frequency ac drive technology. The simulation and experimental results are presented for variable load torque conditions. The variable frequency control scheme is implemented using a DSP- TMS320LF2402. This control reduces the switching losses and current ripples, eliminates the EMI and improves the efficiency of the drive system. Experimental results confirm the consistency of the proposed approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1152-1154
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• 2002

In this paper, a direct torque control method of an induction motor is proposed which enables constant switching frequency. The switching strategy of a conventional direct torque control scheme which is based on hysteresis comparator results in a variable switching frequency which depends on the speed, flux, stator voltage and hysteresis band of the comparator. This paper proposes a new switching strategy which determine the effective switching time on each switching period by comparing the ascending and descending torque slopes. The simulation results are presented to verify this proposed scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.685-688
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• 1992

This paper studies the commutation phenomenon in the Brushless DC Motor with the trapezoidal BEMF waveform. It is shown that the torque ripple am the speed ripple due to the phase commutation depend on driving sytem, operating speed am load condition. The effects of resistance and BEMF flat width on torque ripple are considered. Speed - torque characteristics of the motor is presented considering the phase commutation. Uncommutating current control method can attenuate the torque ripple in the low speed region, and also minimize the switching loss am switching frequency. In this paper, the commutation phenomena are verified by analytical formulation and simulation.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 1989년도 추계학술발표회논문집
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• pp.51-58
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• 1989

In this paper, the technique of particular harmonics elimination in three-phase PWM Inver-ter output waveform and the method for speed control of a squirrel cage I.M. are introduces. The required switching patterns are determind on personal computer and the results are stored in look-up table in EPROM for controlling the switching of the Inverter devices. In this system, the microprocessor(Intel 8086)computes the actual Motor speed from the pulses generated in a Incremental Encoder, compares the actual speed with the reference speed. And the PI(Proportional-Integral) controller is used to adjust the frequency of the Inverter that feeds the Motor.

• 유공압시스템학회논문집
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• 제1권4호
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• pp.15-21
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• 2004

High speed on-off electro-magnetic valves have been used for pressure control or flow control in automotive or construction machine servomechanisms. These systems require quicker valve switching speed to improve control preciseness. The authors designed and manufactured an electric valve driver with quick response characteristics by using 3 power source type valve driver concept. In experiments by using a hydraulic system incorporating the new valve driver, the new driver shortened the switching lag time from 5 ms to 1.3 ms. And also the new driver showed excellent position tracking control performances.

• 한국컴퓨터정보학회논문지
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• 제8권3호
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• pp.163-169
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• 2003

본 연구에서 개발하고자 하는 기기의 모델은 마이크로 컨트롤을 이용하여 모터속도를 제어 할 수 있는 출력 전자 변속기로써, 자동제어 방식을 사용하여 Switching frequency를 1,000MHz까지 가능한 형태로 변환하는 자동 변속장치이다. 연속출력전류는 5A, 11A, 18A, 25A, 35A, 50A이며, 사용되는 전압은 9V에서 최대 18V까지 가능하도록 설계하였다. Micro-controller 의 software와 hardware의 블록 다아이그램을 고안하였으며, 전력손실을 막기 위해 자동적으로 3.7V에서 Auto Cut-Off기능이 있도록 구성하였다.

• 전력전자학회논문지
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• 제5권6호
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• pp.530-536
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• 2000

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권10호
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• pp.693-700
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• 2000

A direct torque control algorithm for 3-level inverter-fed induction motors is presented. Conventional voltage selection methods provoke some problems such as stator flux drooping phenomenon and undersirable torque control appeared especially at the low speed operation. To overcome these problems, a proposed method uses intermediate voltage vectors, which are inherently generated in 3-level inverters. In the proposed algorithm, both subdivision of the basic switching sectors and applications of tntermediated voltages improve the low speed operation characteristics. This algorithm basically considers applications in which direct torque controlled induction motors are fed by 3-level inverters with low switching frequency around 500Hz. An adaptive observer is also employed to bring better responses at the low speed operation, by estimating some state-variables, motor speed and motor parameters which take a deep effect on the performance of the low speed operation. Simulation and experiment results verify effectiveness of the proposed algorithm.

• Journal of Magnetics
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• 제11권2호
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• pp.61-65
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• 2006

The physical origin of complex dynamic domain configuration in nonequilibrium magnetic systems with mesoscopic length scales has been studied. An increasing complexity in the spatial feature of the evolution is found to accompany the increasing reversal speed, when a ferromagnetic element is driven by progressively faster switching fields applied antiparallel to the initial magnetization direction. As reversal rates approach the characteristic precession frequencies of spin fluctuations, the thermal energy can boost the magnetization into local configurations which are completely different from those experienced during quasistatic reversal. The sensitive dependence of the spatial pattern on switching speed can be understood in terms of a dynamic exchange interaction of thermally excited spins; the coherent modulation of the spins is strongly dependent on the rise time of switching pulses.