• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1555-1560
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• 2004

We made a simplified eddy-current-tester, and observed some materials for the ingredients and mass and locations. The tester detects the current as frequency shifts of a LC-resonance circuit, which are caused by the eddy currents. Using air-wick coil and a multi-piled ceramic capacitor, we made a resonance system whose frequency was 100KHz. The shift quantity is few; so, to detect it, we used a frequency counter, and counted the shift. We can detect 10Hz order's shift.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.509-514
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• 2004

This paper introduces the modified slip energy recovery system in order to improve its power factor and to reduce harmonics of line current waveforms. Twelve pulse line commutated converter with the chopper type IGBT is applied where the chopper is applied across the DC terminal and the chopped DC is fed to the converter operating as an inverter and then passed through the wye-wye and delta-wye transformer circuit. This scheme leads to be able to adjust the speed of the motor by the duty cycle of the chopper operating in PWM mode. The fuzzy logic controller is also introduced to the modified slip energy recovery system for keeping the motor speed to be constant when the load varies. The experimental results in testing the 0.22 kW wound rotor induction motor from no-load condition to rated condition show the effectiveness of the proposed control scheme.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.901-904
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• 2005

Testing of mixed-signal circuit has become a difficult task for test engineers and efficient test solution to these problems are needed. In this paper a new specification-based mixed-signal test method called TSS(Time Slot Specification) using high performance current sensors and a novel test point selection technique without heavy computational overhead are proposed. External output and power nodes are used for test points and accessed by the current sensors in the ATE.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.77-79
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• 1996

The model interrupters of $SF_6$ gas electromagnetic contactor whose ratings are 7.2kV, 4.0kA have been designed and manufactured on the basis of theoretical and computational analysis for its development. The eddy current analysis, the magnetic field analysis and the calculation of the rotational force on arcs have been conducted using FLUX2D package. The short circuit current interrupting tests have been conducted for the model interrupters using the simplified synthetic testing facility in KERI. The results show that the model interrupters have sufficient interrupting capability and the new design concept is prefer for good interrupting performance.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.256-259
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• 2003

In this paper describes the development testing results of high density High Voltage Power Supply(HVPS) that employ microwave TWTs. The HVPS consist of number of modules connected in series. A new design that adapt resonant circuit and high density pulse transformer to the high voltage modules makes the HVPS much more reliable. Also High voltage Solid-State modulation using fast switching devices(FET's) and the test results of modulator modules development are represented.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.951-955
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• 2004

Piezoelectric(PZT) actuator can substitute for solenoid which is used in fluid control field because it has faster response times and no possibility of explosion. Besides, it is available in a high temperature and it has low energy consumption. In this study, pneumatic micro valve, bimorph type PZT actuator using the softner type PZT, carbon plate as a shim and its controller circuit were suggested and investigated. Performance tests and characteristics analysis, such as displacement, force, hysteresis and frequency properties, were carried out. The displacement of the actuator measured at the end point was 63 ${\mu}m$., force of the actuator was 0.052 N and maximum operating frequency was 15Hz. Also, characteristics of the micro valve with PZT actuator were evaluated in a testing system. The results show that the suggested PZT actuator is suitable for micro valve.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.5-8
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• 2008

SOFC (Solid oxide fuel cell) has an advantage in the term of fuel flexibility, comparing with other kinds of fuel cells. In SOFC and fuel reformer cooperation system, the reformate gas with the various $H_2$/CO ratios is delivered into the anode of SOFC. In this situation, electrochemical oxidation reactions of the reformate gas in the anode are complex and competitive. In this paper, the effects of the composition of $H_2$ and CO on the overall electrochemical oxidation at Ni-YSZ anode are studied by testing the open circuit voltage (OCV) and current-voltage characteristics of single cells.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.277-279
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• 2002

This paper is an experimental research of the design of a cell battery charger using switching methods. The developed charger in this paper can do both the equalizing current charge and floating charge. Also, it is easily transferable. Power MOS FET was used for the full bridge converter of the charger, and ZVS was applied for the switching method of the converter. Also, Customized IC was used for the control circuit in order to simplify ZVS mode. The setting current and floating current used for the charger were designed by using OP AMP. Based on the process provided by the current research, a sample converter with the power rating of 5KVA was developed and is field-testing to improve its validity and stability.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.7
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• pp.32-39
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• 1999

Digital signal processor (DSP) is used to obtain the peak value and the time difference of ultrasonic signals, to make digital filter, and to derive mathematical transformation from analog circuit. In this study, C-scan system and control program have been developed to high speed data acquisition. This system consists of signal processing parts (DSP, oscilloscope, pulser/receiver, digitizer), scanner, and control program. The developed system has been applied to a practical ultrasonic testing in overlay weld, and demonstrated high speed with precision

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2099-2104
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• 2015

The paper presents a monitoring system for the cooling of distribution transformers. The suggested system is controlled by a microcontroller scheme. The system is designed to control the oil temperature. It gives a solution to improve the cooling system by adding a number of fans especially for indoor transformers that are placed in badly-ventilated rooms. Also, the paper includes an alarm system with the possibility of tripping the transformer if it is necessary. The monitoring system consists of acquisition temperature sensor, and on-site unit. The hardware and software of the on-site unit are demonstrated with sufficient illustrations. Small prototype is constructed in the laboratory. Some laboratory experiments are carried out for examining the designed circuit by using Proteus Virtual System Modeling as well as for testing the prototype monitoring system. Concerning this research point, a study is carried out to evaluate the economic feasibility. The results are recorded and associated with many recommendations that may be valuable to electrical distribution (utility) companies.