• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.406-408
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• 1999

In order to reduce the overall size and cost, researchers attempted to integrate the functions of power factor correction(PFC) and isolated dc-dc conversion into single power stage. However, single-stage isolated PFC converters have higher voltage stress and heavier loss when compared with a normal dc-dc converters. In this paper, we propose to add active clamping circuit to keep the switch voltage stress low and to achieve soft switching of electronic devices.

• Korean Journal of Clinical Laboratory Science
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• v.45 no.2
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• pp.60-65
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• 2013

Data from repeated measurements are accomplished through repeatedly processing the same subject under different conditions and different points of view. The power of testing enhances the choice of pertinent analysis methods that agrees with the characteristics of data concerned and the situation involved. Along with the clinical example, this paper compares the analysis of the variance on ex-post tests, gain score analysis, analysis by mixed design and analysis of covariance employable for repeating measure. Comparing the analysis of variance on ex post test, and gain score analysis on correlations, leads to the fact that the latter enhances the power of the test and diminishes the variance of error terms. The concluded probability, identified that the gain score analysis and the mixed design on interaction between "between subjects factor" and "within subjects factor", are identical. The analysis of covariance, demonstrated better power of the test and smaller error terms than the gain score analysis. Research on four analysis method found that the analysis of covariance is the most appropriate in clinical data than two repeated test with high correlation and ex ante affects ex post.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.2
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• pp.220-220
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• 1999

This paper describes the high efficiency inverter ballast circuit using very cheap microprocessor, which has been developed by the author. A variety of soft-switching techniques have been proposed to reduce the switching losses and EMI problems that occur with higher switching frequencies in switched inverter ballast. The inverter ballast circuit, which employs a temperature sensing circuits has been also proposed to improve starting performance of the fluorescent lamps. That is, the inverter ballast circuit, which employs a soft-starting circuit and soft-switching techniques to implement the power factor correction and to mitigate of power-loss and increase a life time of the fluorescent lamps, has become an attractive performance for ballasting the fluorescent lamps. In this paper, the operation and the control of the inverter ballast are described in detail and experimental results are presented. As the experimental results, when environment temperature is at -40℃, the inverter ballast circuit has low THD(4.8%) of the input current and large power factor(98%) of the lamp current. The proposed improved ballast circuit appears to be a good performance for ballasting fluorescent lamps.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.4
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• pp.24-32
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• 2009

For a design of on/off solenoid actuator for valve actuating, designer must have the experimental knowledge as well as general electromagnetic formulas to design object. It is possible for theoretical knowledge to do the out-line design, but it is impossible to optimal design without experimental knowledge which only can be achieved through many repeated experiments. In addition, in present on/off type solenoid actuator field, the smaller, lightening, lower consumption power, high response time are effected as the most important design factor. So, experimental knowledge is more needed for optimal design of solenoid actuator. In this study, we derived the governing equations for optimal design of on/off solenoid actuator for valve actuating and developed a design program composed electromagnetic theories and experimental parameter values for inexperienced designers. And we proved the propriety of this program by experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.3063-3068
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• 2014

Since the RCS(Radar Cross Section) of target is important factor to determine radar performance, it is important to locate radar where large RCS is observed. However, the distance between the target and the radar is an important factor of the received power, as well as RCS. In this paper, it is calculated that received power from ballistic missile to radar based on different observed position and it is studied that to place radar for high detection efficiency.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.372-376
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• 2001

Due to several advantages of Pulse Width Modulation(PWM) Converter, such as unity power factor operation, elimination of low-order harmonics and regeneration of motor braking energy to source, the application range of PWM Converter has been rapidly extended in industrial application. Nowadays, vector control algorithm and space vector PWM(SVPWM) method are applied to improve the performances of PWM Converter, but vector control algorithm and SVPWM require to use Microprocessor and other digital devices in hardware, causing costly and somewhat large dimension system. In every practical application of energy conversion equipments, the design and implementation should be carried out considering cost and performance. High performance and low cost is the best choice for energy conversion equipments. So, this paper presents the practical design method and implementation results of 3-phase PWM Converter with analog hysteresis current controller, and verifies the performances of unit power factor operation and energy regeneration operation via experimental results.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.178-179
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• 2017

Input filter is an essential component in a practical matrix converter (MC) system to generate the sinusoidal input currents. However, the input filter causes a displacement angle between the input current of MC and the source current. In this paper, we investigate the input filter design for MCs by considering the displacement angles of the input current and the input voltage to guarantee high input power factor (IPF) operation as well as low input current harmonic contents. Simulation results are provided to validate the input filter design with near unity input power factor and low total harmonic distortion (THD) of the input current.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.205-210
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• 2001

A new single stage power factor corrected AC/DC converter has been proposed, that is unified with buck topology and suitable for universal input. The design example of the proposed converter lot 5V 12A application has been presented. The design considerations and simulation results for the proposed converter have been shown. The simulation results show that the line input current harmonics can meet IEC 1000-3-2 Class D requirements for the line input voltage from 90 to 260V.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.508-513
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• 2014

Heavy load start but light load operation is a common case in practical drive applications. When an induction motor is employed for such applications, its rated power is usually chosen according to the heavy load start. Then, during light load operation, its efficiency and power factor are low. To solve this problem, it is proposed to adjust the motor windings from the startup to the normal operation conditions. In this paper, arrangement of the adjustable windings is introduced, air gap field with different windings is investigated, and steady state operation performance under various loads is examined. It can be seen that by using proper winding arrangement both startup and operation performances are satisfactory.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.232-233
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• 2012

This paper presents an effective control scheme for an electric vehicle battery charger where a symmetrical bridgeless power factor-corrected converter and a buck converter are cascaded. Both converters have been popular in industries because of their high efficiency, low cost, and compact size, hence combining these converters makes the overall battery charging system strongly efficient. Moreover, this charger topology can operate at universal input voltage and attain a desired battery current and voltage without ripple. In order to achieve a unity input power factor and zero input current harmonic distortion, the proposed control scheme adopts duty ratio feed-forward control technique in both current and voltage control loop. Additionally, in the current loop, its reference is created by a phase-locked loop (PLL) block, leading to a pure sinusoidal input current although the input voltage waveform is being distorted. The feasibility and practical value of the proposed approach are verified by simulation and experiment with an 110V/60Hz ac line input and 1.5kW-72V dc output of the battery charging system.