• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.41-48
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• 2009

This paper presents an Neural Network(NN) controller for Maximum Power Point Tracking (MPPT) of PV supplied DC motor. A variation of solar irradiation is most important factor in the MPPT of PV system. That is nonlinear, aperiodic and complicated. NN was widely used due to easily solving a complex math problem. Proposed photovoltaic system consists of NN, DC-DC converter, DC motor and load(cf, pump). NN algorithm apply to DC-DC converter through an Adaptive control of Neural Network, calculates Converter-Chopping ratio using an Adaptive control of NN. The results of an Adaptive control of NN compared with the results of Converter-Chopping ratio which are calculated mathematical modeling and evaluate the proposed algorithm. The experimental data show that an adequacy of the algorithm was established through the compared data.

• Journal of Korean Society for Atmospheric Environment
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• v.17 no.4
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• pp.313-319
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• 2001

The development of ozone SRP (Standard Reference Photometer) designated as a G-7 project by the Korean Ministry of Environment began 1997 and is now nearly completed. With the completion of the ozone SRP we will not only acquire a qualification to participate in the international ozone calibration system but also enhance calibration credibility of ozone similarly to that of other ambient air pollution monitors. As the ozone SRP uses highly cleaned blank air that can be distinguished from general ozone analyzer, it is possible to reduce errors associated with the determination of ozone via elongation of the absorption length as long as 1 meter In addition, gas chopping method hat been adopted to cut down interference of other substances and time drift. Furthermore, the system has also been modified to minimize the strayed ultra-violet noise along the light path. In this paper, a new method for uncertainty evaluation has been introduced, which is guided by the ISO (International Standard Organization) GUM (Guide to the Expression of Uncertainty in Measurement) through assessments of the uncertainty type B (that was impossible to estimate before) as well as the uncertainty type A (based on statistics).

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.28-32
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• 2004

In this paper, the operational performance of SRM can be improved by using current hysteresis control method. This method maintains a generally flat current waveform. At the high speed, the current chopping capability is lost due to the development of the back-EMF. Therefore SRM operates in single pulse mode. By using zero-current switching and zero-voltage switching technique, the stress of power switches can be reduce in chopping mode. When the commutation from one phase winding to another phase winding, the current can be zero as fast as possible in this period because several times negative voltage of DC-source voltage produce in phase winding. This paper is compared to performance based on conventional C-dump converter topology and the proposed resonant C-dump converter topology Simulation and experimental results are presented to verify the effectiveness of the proposed circuit.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.207-210
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• 2001

Recently, the study on the vibration analysis of machinery is greatly important and ESPI is widely used because of its many attractive features. Firstly, ESPI can be used to measure the vibration mode shape and the phase in real-time. Secondly, the conventional measuring methode, such as accelerometers, take much time to measure the whole field of object, but ESPI needs shorter time than other methods. Because ESPI is a field-inspection method. Thirdly, ESPI is a non-contact measuring system. ESPI does not have influence on the specimen. Beyond these features, there are several advantages in ESPI system. In this paper, the Stroboscopic ESPI system is described for measurement of a vibration mode shape. The Stroboscopic ESPI system had been used to visualize the vibration mode shape, in which EO(Electro-Optic)modulator was used to chop CW(Continuous Wavefront)laser. But it was not easy to control EO modulator and quantified the vibration amplitude and the phase of circular metal plate. At first, we found resonant frequency of the specimen by using time-averaged ESPI method. Nextly, the amplitudes of specimen were quantified by using Stroboscopic ESPI and we compare the results which were obtained in several chopping ratio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.4
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• pp.459-466
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• 2014

This paper deals with the method to classify the aircraft target by analyzing its JEM signal. We propose the method to classify the engine model by analyzing JEM spectrum using the harmonic frequency mask generated from the blade information of jet engine. The proposed method does not need the complicated logic algorithm to find the chopping frequency in each rotor stage and the pre-simulated engine spectrum DB used in the previous methods. In addition, we propose the method to estimate the precise spool rate and it reduces the error in estimating the number of blades or in calculating the harmonic frequency of frequency mask.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1697-1699
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• 2001

In this paper, the circuit of AC Choppers for $CO_2$ laser power supply are proposed and investigated. IGBT-controlled ac voltage regulators, operating at high frequency chopping mode. Chopping-to-supply duty ratio plays an important role in terms of laser output. Laser input energy is varied by controlling the leakage transformer used with the proposed system. This improved circuit employs a 3 electrode - type and Ring Blower. This improved circuit system has many advantages compared with the conventional SMPS such as simple design requirement, easy implementation, high reliability, low switching loss, and consequently high efficiency. As a result, the maximun output was 16W at duty-ratio of 92%, total gas mixture of $CO_2$ : $N_2$ : He = 1 : 9 : 15, total pressure of 15torr.

• Carbon letters
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• v.15 no.3
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• pp.180-186
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• 2014

This study highlights a novel method and mechanism for the rapid and effective milling of carbon fibers (CFs) in silicon carbide (SiC) powder, and also the dispersion of CFs in SiC powder. The composite powders were prepared by chopping and exfoliation of CFs, and ball milling of CFs and SiC powder in isopropyl alcohol. A wide range of CFs loading, from 10 to 50 vol%, was studied. The milling of CFs and SiC powder was checked by measuring the average particle size of the composite powders. The dispersivity of CFs in SiC powder was checked through scanning electron microscope. The results show that the usage of exfoliated CF tows resulted in a rapid and effective milling of CFs and SiC powder. The results further show an excellent dispersion of CFs in SiC powder for all CFs loading without any dispersing agent.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.27-33
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• 2016

This paper proposes a Low Noise Amplifier (LNA) with chopper stabilization technique with a sample-hold circuit. Chopper stabilization technique is effective in terms of reducing low frequency offset and flicker noise. Conventional chopper amplifier has a disadvantage in area because of using Low Pass Filter (LPF) for remove chopping spike. The proposed chopper amplifier employed sample and hold technique to decrease chopping spike instead of LPF that improves 36% in voltage damping and 11% in area.

• Journal of Power Electronics
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• v.7 no.1
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• pp.64-71
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• 2007

This paper proposes a novel active frequency drift (AFD) method to improve the islanding detection performance with minimum current harmonics. To detect the islanding phenomenon of grid-connected photovoltaic (PV) inverters concerning the safety hazards and possible damage to other electric equipment, anti-islanding methods have been described. The AFD method that uses chopping fraction (cf) enables the islanding detection to drift up (or down) the frequency of the voltage during the islanding situation. However, the performance of the conventional AFD method is inefficient and causes difficulty in designing the appropriate cf value to meet the limit of harmonics. In this paper, the periodic chopping fraction based on a novel AFD method is proposed. This proposed method shows the analytical design value of cf to meet the test procedure of IEEE Std. 929-2000 with power quality and islanding detection time. To verify the validation of the proposed method, the islanding test results are presented. It is confirmed that the proposed method has not only less harmonic distortion but also better performance of islanding detection compared with the conventional AFD method.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.64-66
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• 2002

Recently. switched reluctance motor is noticed because it is simple in structure and mechanically strong. SRM has great competitive power, and the study is developed about improving the characteristics of SRM. The current density of winding becomes larger in designing SRM that has the characteristics of the low voltage and high current. Hence the current density of SRM of a vehicle is high. And in order that we drive SRM in variable speed and protect the switching device. the current of SRM is limited by chopping. So it is impossible to obtain object value of output characteristics by limited current. In this paper, the author design the shape of SRM from Miller's output equation, and verify the design of SRM by using FEM. The waveform of chopping current is predicted by simulation and concur with experimental result. And the torque is improved by applying overlap current.