• Journal of Electrical Engineering and Technology
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• 제3권4호
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• pp.576-583
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• 2008

In this study, we attempt to design a real-time autonomic nervous system(ANS) evaluation system usable during exercise using heart instantaneous frequency(HIF). Although heart rate variability(HRV) is considered to be a representative signal widely used ANS evaluation system, the R-peak detection process must be included to obtain an HRV signal, which involves a high sampling frequency and interpolation process. In particular, it cannot accurately evaluate the ANS using HRV signals during exercise because it is difficult to detect the R-peak of electrocardiogram(ECG) signals with exposure to many noises during exercise. Therefore, in this study, we develop the ground for a system that can analyze an ANS in real-time by using the HIF signal circumventing the problem of the HRV signal during exercise. First, we compare the HRV and HIF signals in order to prove that the HIF signal is more efficient for ANS analysis than HRV signals during exercise. Further, we performed real-time ANS analysis using HIF and confirmed that the exerciser's ANS variation experiences massive surges at points of acceleration and deceleration of the treadmill(similar to HRV).

• 설비공학논문집
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• 제10권5호
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• pp.619-629
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• 1998

An experimental work was conducted to investigate a feasibility of simultaneous measurement of gas-liquid two-phase flowrates with double orifice plates using air and water. The tests were carried out under the atmospheric pressure and at the ambient temperature using two different tube sizes. Qualities of an air-water flow in the present study have values less than 0.1 and thus the mixed flow showed bubbly, plug, slug flow regimes. The probability density function (PDF) and the power spectral density function (PSDF) of the instantaneous pressure drop traces for the flow regimes were obtained. It is found that some distinctive features exist in the distribution of these functions, depending upon the two-phase flow pattern. The time-averaged value of the instantaneous pressure drop increases with increasing gas and liquid flowrates, showing a single-valued function for the total mass flowrate and the quality. It is also found that the two-phase discharge coefficient exhibits a consistent trend for variation of dimensionless parameters such as the superficial velocity ratio and the gas Reynolds number. The results indicate that simultaneous measurement of two-phase flowrate may be possible based upon a statistical analysis of the instantaneous pressure drop curves monitored using double orifice plates.

• 전력전자학회논문지
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• 제22권5호
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• pp.457-462
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• 2017

This paper proposes a digital power control of the LLC resonant half-bridge inverter for high power microwave oven application. Conventional half-bridge inverter for driving a microwave oven uses a hardware-based power control method which varies the frequency according to the AC source voltage. In this case, it is difficult to control the output power according to the variation of the load status of magnetron. The proposed power control consists of an instantaneous current generator and a current controller. Instantaneous current generator makes an instantaneous current reference from power command using input voltage information. Current controller controls input current which has an information of status of magnetron. The proposed power control does not require any compensation algorithm for the change of the load status of the magnetron and change of input voltage. The validity of the proposed method for the control of the change of input voltage and frequency is verified by both simulation and experiment.

• Current Optics and Photonics
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• 제4권4호
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• pp.361-367
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• 2020

An approach based on an integrated photonic Ti:LiNbO₃ Y branch has been proposed, designed, and analyzed for the microwave instantaneous frequency measurement (IFM). By designing the Y branch with length L = 6545 ㎛ and refractive index N_TE - N_TM = 0.0764, a complementary optical filter with free spectral range (FSR) of 600 GHz is constituted, which results in a maximum measureable frequency of 300 GHz being obtained. Theoretical analysis on the temperature stability of the Ti:LiNbO₃ Y branch shows that the FSR variation of the complementary filter is 0.3% for the temperature change of 100 K, which indicates that the IFM approach will have a better stability. All these results demonstrate that the proposed IFM approach has potential capability to be used for the increasingly higher microwave IFM with better stability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.412-414
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• 1996

The rotor resistance variation has a large effect on the field oriented control system of induction machine. In this paper, the adaptation technique based on MRAC is used to identify the rotor resistance variation. The criterion function used in the adaptation algorithm is the error function of the two reactive powers of the induction motor. The one is obtained from the voltages and the currents of the stator of the induction motor. And the other is estimated from the rotor flux and stator current. We simulated this control system operated by field oriented control and assured the robustness of the induction motor control system against the rotor resistence variation.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1210-1216
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• 2014

This paper deals with an application of Teager Energy Operator (TEO) and Energy Separation Algorithm(ESA) to detect and determine various voltage waveform distortions like harmonics, inter-harmonics and frequency variation. Because the TEO and DESA algorithm was initially proposed for speech or communication analysis, its applications are limited to some types of waveform in the power quality analysis area. For example, an undistorted voltage signal is similar with a pure sinusoid. A voltage fluctuation is very similar with an amplitude-modulated signal, from the viewpoint of signal theory. And a continuous frequency variation is similar with a frequency-modulated signal, which is also known as a chirp signal. This paper is written to show that the TEO and DESA algorithm can be used for detecting occurrences of the representative waveform distortions and determining their instantaneous information of amplitude and frequency.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1124-1136
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• 2017

Direct Power Control technique has become popular in the grid connected Voltage Source Converter (VSC) applications due to its simplicity, direct voltage vector selection and improved dynamic performance. In this paper, a direct method to determine the effect of voltage vector on the instantaneous active and reactive power variations is developed. An alternative Look Up Table is proposed which minimizes the commutations in the converter and results in minimum reactive power variation. The application of suggested table is established for Shunt Active Power Filter (SAPF) application. The Predictive Direct Power Control method, which minimizes apparent power variation, is further investigated to reduce commutations in converters. Both the methods are validated using 2 kVA laboratory prototype of Shunt Active Power Filters (SAPF).

• Journal of Advanced Marine Engineering and Technology
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• 제31권4호
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• pp.433-440
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• 2007

In this paper a new dynamoelectric winch system is introduced which is widely applied in shipping. building, architecture and so on. Generally in the winch system the squirrel cage induction motor is used as prime mover and line voltage is directly applied to the induction motor during operation. So it is difficult to obtain the smoothing revolution. because of variation of the weight of cargo and system operating method. Based on above reasons, the switched reluctance motor (SRM) is proposed to replace the induction motor because of more reliable mechanical structure, better traction characteristic and higher efficiency compared to induction motor. And in order to solve smoothing revolution problem, instantaneous torque control method based on torque sharing function (TSF) is used. Finally the validity of the proposed method is verified through the simulation and experimental results.

• 지구물리와물리탐사
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• 제4권4호
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• pp.115-123
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• 2001

탄성파 중합 단면도 상에서 천연가스 부존 여부를 지시하는 명점(bright spot)은 가스 층이외에 음향계수 차이가 큰 지층에서도 나타나므로 가스 층여부를 판단하기 위해서는 속도분석, AVO 분석, 탄성파 복소 트레이스 분석 등 추가적인 정밀 자료처리가 필요하다. 본 연구에서는 가스 층 추정을 위해 정밀 속도분석과 트레이스 복소분석 그리고 입사각에 따른 진폭변화 결과인 탄화수소 직접 지시 단면도(DHI)분석을 실시하였다. 트레이스 복소분석은 지층 상$\cdot$하간의 물성변화에 따른 지질정보를 제공하는것으로 여기에서는 순간 진폭, 순간 진폭에 대한 1차 및 2차 미분 값, 순간 위상, 순간 주파수, 가중평균 순간 주파수 값을 구하여 시추가 이루어진 국내 대륙붕 탄성파 자료에 적용하였다. 자료처리 결과 가스가 부존할 가능성이 높은 지역에서는 순간 진폭, 순간 주파수 단면도 그리고 AVO 분석에 의한 DHI 단면도에서 공통적으로 탄성파 진폭이상이 나타나며 정밀 자료처리 결과 중 어느 한 곳이라도 진폭이상이 나타나지 않으면 가스 부존 가능성이 낮다고 할 수 있다.

• 전력전자학회논문지
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• 제4권1호
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• pp.50-56
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• 1999

본 연구에서는 시간영역에서 전력이 해석되어지므로 이해하기 쉽고, 비교적 계측하기 용이한 상관함수에 의한 순시전력이론에 대해서 고찰하였다. 상관함수에 의한 순시전력이론은 시간영역에서 전압과 전류의 자기상관함수와 상호상관함수에 의해서 전력과의 전압과 상관성에 따라 상관전력과 비상관 전력으로 분해된다. 분해된 두 가지 전력성분으로부터 비선형 부항의 특성에 따라 전력과 전류를 유효성분, 기본파 무효성분 그리고 고조파성분 등 3성분으로 분해한다. 능동전력필터는 그 보상특성상 전력과 전류의 3성분만을 다루며, 실시간 제어를 위해 그외의 여러 복잡한 그리고 구현의 어려움이 있는 전력모델은 경제적이지 못하다. 상관함수적인 순시전력이론에 의해 분석된 전력성분들의 타당성을 입증하기 위해서 전압형 DSP능동전력필터를 제작하였다. 싸이리스터 제어 유도전동기 구동시스템의 전력을 제안된 순시전력이론에 의해 3성분으로 분해한 후, 이들 성분중에서 보상기준전류로 고조파성분과 기본파 무효성분을 각각 제어하여 그 보상결과로부터 타당성을 입증하였다.