• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.153-156
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• 2004

This paper presents a new circuit topology of the half-bridge resonant inverter. As the proposed half-bridge inverter can be operated in the load freewheeling modes, pulse width modulation (PWM) control method can be used for the output power control. The proposed half-bridge inverter should keep unity output displacement factor under the load-impedance varying conditions, if a new PWM control scheme based on the resonant frequency tracking algorithm is adopted. In this paper, electrical characteristics, and losses analysis of the proposed half-bridge resonant inverter are described. Simulation and experimental results of the prototype experimental setup to verify the validity of the proposed half-bridge resonant inverter are presented and discussed.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권6호
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• pp.842-846
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• 2016

This paper presents a DC-DC buck converter which uses a sleep control to improve the power efficiency in a few mW light load condition. The sleep control turns off analog controller building blocks to reduce the static power losses during the off-duty period of pulse width modulation. For verification, a buck converter has been implemented in a $0.18{\mu}m$ CMOS process. The power efficiency has been improved from 76.7% to 82.5% with a 1.2 mW load. The maximum power efficiency is 95% with a 9 mW load.

• Asian-Australasian Journal of Animal Sciences
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• 제14권8호
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• pp.1062-1066
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• 2001

Studies were carried out on forty young bulls of the Hariana breed (around 18 months of age) selected on the basis of their dam's milk yield at the animal farm of CCS HAU, Hisar during the period 1993-1999. Since animals showed variation in capacity to work over prolonged periods, they were subjected to regimes of carting without load and with 8 qtls. of load for three hours. The study revealed that maximum change took place in the pulse rate, followed by respiration rate and rectal temperature. The mean fatigue score for pulling an empty cart ranged between 1.66 to 2.20 after two hours work, and 2.36 to 2.73 after three hours work. For a cart loaded with 8 qtls., the corresponding ranges were 2.90 to 3.36 and 3.40 to 4.10, respectively. These results indicated that the animals under experiment had the capacity to pull moderate load (8 qtls.) for about two hours without showing any serious effect on the ability to recover and soon to work again.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.343-346
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• 2002

In recent, complex SVPWM (Space Vector PWM) algorithm can be easily implemented by high performance microprocessor and DSP. Various SVPWM techniques are widely studied due to the advantages of low harmonic distortion and high use ratio of D.C. link voltage. Most of various studies for improving of VS-PWM inverter performance are concentrated about switching pattern and zero pulse pattern split algorithms. However, dc link voltage that is determined at rated load and speed conditions is not proper in the low speed and under rated load. In this paper, analysis of current ripple with digitally implemented SVPWM inverter is introduced according to link voltage. The optimal link voltage in the designed inverter system and load condition is provided in order to suppress output voltage error and current ripple. As remaining the effective voltage vector interval per sampling period sufficiently, additional voltage error and current ripple are suppressed. The proposed algorithm is verified through digital simulation and experimental results.

• 한국초전도ㆍ저온공학회논문지
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• 제21권4호
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• pp.44-47
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• 2019

This paper is a study of recovery under load process of superconducting fault current limiter (SFCL). SFCL consists of five parallel-connected high-temperature superconductor (HTS) tapes additionally stabilized by stainless tape. Previously, HTS was heated by current pulse to simulate a short circuit in a power grid. During the cooling period, the current amplitude decreased to 23% or less of HTS critical current value, which is the simulation of network re-switching. When HTS with a polymer coating is cooled, temperature gradient on thermal insulation layer occurs, that prevents a boiling crisis and improves the heat sink into liquid nitrogen. Two samples are coated with a 30 ㎛ and 50 ㎛ polylactide (PLA) layers, reference sample has no polymer coating on it. Samples with a polymer coating show 3-5 times faster cooling than the reference one.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권4호
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• pp.246-255
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• 2000

This paper deals with a novel full digital control method of the three-phase PWM inverter for UPS. The voltage and current of output filter capacitor as state variables are the feedback control input. In addition, a double deadbeat control consisting of a d-q current minor loop and a d-q voltage major loop, both with precise decoupling, have been developed. The switching pulse width modulation based on SVM is adopted so that the capacitor current should be exactly equal to its reference current. In order to compensate the calculation time delay, the predictive control is achieved by the current·voltage observer. The load prediction is used to compensate the load disturbance by disturbance observer with deadbeat response. The experimental results show that the proposed system offers an output voltage with THD less than 2% at a full nonlinear load.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.40-44
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• 2002

In this paper, robust control method using fuzzy PI parameter tuning is proposed to control constant thrust force on load variation. First, a structure and thrust force equations of the LPM are described. Second, an controller with PI parameter-tuning using a fuzzy theory is proposed to achieve high-precision position with constant thrust force of the LPM. Finally, the effectiveness of an fuzzy PI controller is demonstrated by some simulated and experimental results. Accurate tracking response and superior dynamic performance can be obtained due to the powerful on-line Fuzzy PI gain tuning method with regard parametric variations and load thrust force variations.

• Journal of Power Electronics
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• 제19권5호
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• pp.1153-1161
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• 2019

A current sharing controller is proposed in this paper for parallel-connected converters. The proposed controller is based on the calculation of the magnitudes of system current space vectors. Good current distribution between parallel converters is achieved with only one Proportional-Integral (PI) compensator. The proposed controller is analyzed and the circulating current impedance is derived for paralleled systems. The performance of the new control strategy is experimentally verified using two parallel connected converters employing Space Vector Pulse Width Modulation (SVPWM) feeding a passive RL load and a 2.2 kW three-phase induction motor load. The obtained test results show a reduction in the current imbalance ratio between the converters in the experimental setup from 53.9% to only 0.2% with the induction motor load.

• 전자공학회논문지SC
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• 제45권6호
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• pp.117-122
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• 2008

맥진은 한의 진단에 있어 중요한 요소이나 맥진 교육에 있어서 수련자와 교육자 간에 언어적 표현 외에는 적절한 교육 정보 소통의 도구가 없어 정량적이며 과학적 교육이 어려운 실정이다. 이에 본 논문에서는 맥진 시 한의사가 세 손가락을 통해 맥진 부위에 가하는 가압력 프로파일을 정량적으로 측정할 수 있는 하드웨어와 이를 기반으로 맥진 동작을 트레이닝할 수 있는 프로그램을 개발하였다. 가압력 프로파일 측정 하드웨어는 인조 팔 속 맥진 위치에 놓인 3개의 로드셀과 맥진 가압력 신호를 증폭하는 증폭부 및 상용 A/D 변환 모듈인 NI-USB 6009로 구성하였으며, 3채널 가압력 신호는 200Hz로 샘플링하였다. 하드웨어 출력 신호를 질량 값으로 교정할 수 있도록 $50{\sim}500g$ 범위의 8개 추를 인조 팔에 올려놓았을 때의 질량 대비 출력전압 테이블을 작성하였다 또한, 이 시스템을 통해 한방 전문의 3명의 맥진 가압 프로파일을 각 3회씩 측정해 보았으며, 이를 통해 한의사의 맥진은 크게 3개의 구간으로 나눌 수 있고 최대 가압력이 약 $500g{\cdot}f$인 것 등을 알 수 있게 되었다. 맥진 가압트레이닝 프로그램은 LabView를 통해 구현하였으며, 수련자가 미리 저장된 목표 맥진 가압 프로파일과 유사하도록 인조 팔을 맥진할 때의 가압 프로파일이 목표 가압 프로파일과 유사한 정도를 평가하여 일정 범위를 벗어나면 경고하고, 실습이 끝나면 목표 프로파일과 유사도 점수를 화면에 표시하도록 하였다. 더 나아가 유사도 점수의 추이를 통해 숙련 추이를 관찰 할 수 있도록 하였다. 이 시스템을 맥진 교육에 활용한다면 보다 정량적이며 과학적인 교육이 가능해질 뿐만 아니라 교육의 효율도 크게 향상될 것으로 기대된다.

• 오토저널
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• 제13권5호
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• pp.51-64
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• 1991

In this paper, an attempt is made to analyze the impulsive stress directly underneath the concentrated impact point for a supported square plate by using the three-dimensional dynamic theory of elasticity and the potential theory of displacement (stress function) on the supposition that the load, F$_{*}$0 sin .omega.t, acted on the central part of it. The results obtained from this study are as follows: 1. The impulsive stress cannot be analyzed directly underneath the acting point of concenrated impact load in privious theories, but can be analyzed by using the three-dimensional dynamic theory of elasticity and the potential theory of displacement. 2. Theorically, with increasing the pulse width of applied load, it was possible to clarify that the amount of stress in the point of concentrated impact load was increased and that of stress per unit impulse was decreased. 3. The numerical inversion of laplace transformation by the use of the F.F.T algorithm contributes the reduction of C.P.U time and the improvement of the accuracy or results. 4. In this paper recommended, it is found that the approximate equation of impact load function P (.tau.) = A.tau. exp (-B.tau.), and P (.tau.) =0.85A exp (-B.tau.) sinC.tau. could actually apply to all impact problem. In compared with the experimental results, the propriety of the analytical method is reasonable.