• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.276-278
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• 2007

This paper describes the analysis to install an arrester for an underground distribution line effectively. Currently, the underground distribution cable is protected by the arrester connected with overhead distribution line. However, riser pole arrester can't protect all parts of cable like the end of the underground distribution cable. To solve this problem, we installed the arrester on each cable and have measured the overvoltage made by lightning surge in each situation. The location to get effective results has been decided from the measured voltage above.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.8
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• pp.804-811
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• 2009

This paper deals with the relationship between zeros and step response of the second and third order LTI(Linear Time Invariant) SISO(Single-Input and Single-Output) systems. As well known, if a system has a single unstable zero, it shows the step response with undershoot and, on the other hand, a stable zero slower than the dominant pole causes the system to have the step response with overshoot. Generally, in the case of a system with two unstable real zeros, it is known to have B type undershoot[7]. But there are many complex cases of the step response extrema corresponding to zeros location in third order systems. This paper investigates the whole cases depending on DC gains of the additive equivalence systems and they are to be classified by the region of zeros which are related to the shape of the step response. Moreover, monotone nondecreasing conditions are proposed in the case of complex conjugate zeros as well as the case of two stable zeros.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1846-1849
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• 2002

A shorted-turn test was performed at the Sininchon combined cycle power plant on gas turbine generators. The test was conducted using a permanent flux probe and on-line diagnosis system. The flux probe installed in the generator air gap senses the field winding slot leakage flux and produces a voltage proportional to the rate of change of the flux. This pattern of flux variation is a signature unique to each field winding. We have also applied a voltage waveform analysis technique that can identify the pole location, slot number and number of shorted-turn with each slot.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1721-1724
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• 1998

A shorted-turn test was performed at the Pyungtaek combined cycle power plant on gas. turbine generator #4. The test was conducted using a permanent flux probe and digital oscilloscope. The flux probe installed in the generator air gap, senses the field winding slot leakage flux and produces a voltage proportional to the rate of change of the flux. This pattern of flux variation is a signature unique to each field winding. We have also applied a waveform analysis technique that can identify the pole location, slot number, and number of shorted-Turns with each slot.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.11
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• pp.742-747
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• 1999

On-line diagnosis system has been developed and is now applied the detection of shorted turns in the field winding of large generator. This system consists of data aquisition system and display PC. The data aquisition system detects voltage waveforms from flux probe sensor installed in the stator slot. The display PC shows theshorted-turn situation of generator rotor winding. A shorted-turn diagnosis test wasperformed on five gas turbine generators at the Seoinchon combined cycle power plant. The test was conducted using an new diagnosis system and digital oscilloscope which can identify the pole location, the slot number and the number of shorted turns within each slot. It is confirmed that results of two systems are very same in the field tests.

• Journal of Power Electronics
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• v.10 no.4
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• pp.382-387
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• 2010

This paper presents a novel design method for determining the PID gains of a speed controller for a servo system compensating variations in bandwidth at a low speed. The variations in bandwidth of a speed controller are measured at a low speed and the relationship between the bandwidth and the damping ratio are verified by determining the location of the closed loop pole. The proposed algorithm uses the z-transform of a plant and speed controller and applies the time-varying sampling method for determining the PID gains of the speed controller at low speed. The magnitude and the phase condition are considered for finding a suitable control gain. The usefulness and effectiveness of the proposed method is demonstrated through experimental results such as low speed control and robust disturbance responses.

• Proceedings of the KIEE Conference
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• 2006.07e
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• pp.59-60
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• 2006

A shorted-turn test was performed at the Pyungtaek combined cycle power plant on gas turbine generators. The test was conducted using a permanent flux probe and on-line shorted-turn diagnosis system. The permanent flux probe installed in the generator air gap senses the field winding slot leakage flux and produces a voltage proportional to the rate of change signature unique to each field winding. We have also applied a voltage waveform analysis technique that can identify the pole location, slot number and number of shorted-turn with each slot.

• Journal of Sensor Science and Technology
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• v.33 no.4
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• pp.209-215
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• 2024

Generally, a straight displacement meter is used to obtain displacement data to verify the safety of structural members and structures. A straight displacement meter is also used to measure the absolute displacement in research laboratories or safety inspection sites such as bridges and buildings. In this study, for structures in which the displacement sensor could not be fixed at the location where the displacement was to be measured, a circular displacement meter was manufactured to measure the displacement by installing a displacement gauge on the structure itself. In other words, when measuring the horizontal displacement of an upper part, such as a wind tower, a circular displacement meter was installed inside the wind tower to integrate it with the structure, applying the principle that the structure itself can be used as a displacement meter. This circular displacement meter can be installed and used inside a circular structure. Whereas in the case of a telephone pole, it can be installed outside to measure displacement. It can be manufactured in various sizes and used.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.8
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• pp.743-750
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• 2016

The conventional track to train communication is commonly using radio based equipment such as transponder or balise to transmit the data. However, there are some drawbacks of the conventional equipment, for example multipath fading, source of bandwidth limitation, and interference from other users. Moreover, the radio based equipment is very expensive when installed in large numbers. To address these problems, we propose infrared system for trackside to train communication system. Infrared system offers a transmission of data to train and it can be processed to obtain at least a train location. Infrared communication protocol provides practical wireless data communication for direct dedication configuration. Furthermore, on the pole configuration the infrared system provides an abundant bandwidth, an economically sensible, minimalized installation of equipment on the trackside and reliability for heavy rain environment. This paper concentrates on the communication function and measurement performance evaluation. The proposed trackside to train communication system covers about 6 meters between infrared receiver and infrared transmitter, whereas the half angle of the transmitter is set to $19.65^{\circ}$ and the receiver angle is $15^{\circ}$.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.44-47
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• 2016

In these days, interest of systems and services using TVWS(TV White Space) are increased, communication systems and services for TVWS have been actively studied. The unoccupied frequency in TVWS is different according to the geographical location and the time of day. RF systems having a frequency tunable bandpass filter operated in TVWS could be efficiently used. In this paper, a frequency tunable bandpass filter operated in 470 ~ 698MHz is designed and implemented. In consideration of simple control and physical size, the tunable bandpass filter is designed with 2-pole. The implemented tunable bandpass filter has the operating frequency band of 470 ~ 698MHz with control voltages of 1.58 ~ 3.93V, the insertion loss of maximum 4.78dB and the return loss of below 10dB. The implemented frequency tunable bandpass filter can be directly used in the RF receiver for TVWS and the design procedures could be used for developing a high power tunable bandpass filter as the basic research data.