• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.77-84
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• 1998

This paper describes a control system design for the transmission STATCOM by applying a no-linear state feedback, and the performance analysis of the control system by simulations and scaled-model experiments. A mathematical model for the STATCOM was derived using a 3-phase equivalent circuit and a perturbation state equation with respect to a typical operating point. A transfer function to describe the dynamics of STATCOM was derived by considering nonlinear state feedback. A controller design was completed by analyzing the feedback system stability with root locus method. The performance analysis of the conceived control system was verified by simulations with the EMTP and experiments with scaled model, assuming that the STATCOM is connected to an 154kV transmission system. The results show that the conceived control system has excellent performance to control the reactive power of the transmission system.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.863-869
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• 2006

The existing Europe Standard, EN 50159 with respect of safety of railway signalling communication protocol has been changed into International Standard, IEC 62280. This Standard presents the requirement for safe communication between safety-related devices which connects with transmission system, there are both closed and open transmission system. Regardless of this international Standards, the communication protocol for interface between CTC communication server and external facilities has been standardized several years ago in our country, so this is applied to integrated CTC system in KORAIL. Two Standards are currently standardized as a protocol between CTC and external facilities, these standard protocols are also required high level safety as a communication link which is transmitted vital control information in common with the train control system. For that reason, we have made analysis of requirement for the safe transmission required by international standard. Under this analysis, we have studied safety features of communication protocol applying to our standard. In other words, we have researched that how many the requirement from international standard for safe transmission is reflected in domestic standard protocol, and also whether our standard makes sure of safety enough or not.

• Journal of Power Electronics
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• v.15 no.1
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• pp.86-95
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• 2015

An active clamp high step-up boost converter with a coupled inductor is proposed in this paper. In the proposed strategy, a coupled inductor is adopted to achieve a high voltage gain. The clamp circuit is included to achieve the zero-voltage-switching (ZVS) condition for both the main and clamp switches. A rectifier composed of a capacitor and a diode is added to reduce the voltage stress of the output rectifier diode. As a result, diodes with a low reverse-recovery time and forward voltage-drop can be utilized. Since the voltage stresses of the main and clamp switches are far below the output voltage, low-voltage-rated MOSFETs can be adopted to reduce conduction losses. Moreover, the reverse-recovery losses of the diodes are reduced due to the inherent leakage inductance of the coupled inductor. Therefore, high efficiency can be expected. Firstly, the derivation of the proposed converter is given and the operation analysis is described. Then, a steady-state performance analysis of the proposed converter is analyzed in detail. Finally, a 250 W prototype is built to verify the analysis. The measured maximum efficiency of the prototype is 95%.

• Tribology and Lubricants
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• v.34 no.6
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• pp.325-331
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• 2018

Automobiles and systems requiring high gear ratios and high power densities generally use worm gears. In particular, as worm gears have a small volume and self-locking function, home appliances such as refrigerators and washers consist of worm gears. We can classify worm gears into cylindrical worms and rectangular worms. According to the AGMA standard, there are four types of cylindrical worms, ZA, ZN, ZK and ZI, depending on the machining of the worm shaft. It is preferable to use a ZI-type worm shaft, which is a combination of a worm wheel having an involute helical tooth surface and a conjugate tooth surface. However, in many cases, industries mostly use ZK, ZN, and ZA worm shafts because of the ease of processing. This paper presents numerical approaches to produce ZI and ZA worm surfaces and worm wheel. For the analysis of the transmission error of a worm gear system, this study (1) generates surface profile functions of ZI profile worm gear and worm shaft based on the common rack theory, (2) adopts the Newton-Raphson method for the analysis of the gear surface contact condition, and (3) presents and compares the corresponding transmission errors of ZI and ZA worm gears.

• Journal of Drive and Control
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• v.15 no.4
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• pp.30-38
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• 2018

Electronic control units (ECUs) are currently popular, and have evolved further towards the high-end application of autonomous vehicles in the automotive industry. Such digital technologies have also become widespread, in agriculture and construction equipment. Likewise, transmission control of high-speed tracked vehicles is based on the transmission control unit (TCU), performing complex gear change control functions, and diagnostic algorithms (a TCU's self-diagnostic and reporting capability of malfunction data through CAN communication). Since all functions of TCU are implemented by embedded-software, it is hardly possible to analyze specifications by reverse engineering. In this paper a real-time transmission simulator adaptable to TCU is presented, for analysis of diagnosis algorithm and standards. Signal simulation circuits are deliberately designed considering electrical characteristics of TCU inputs and various analysis tools, such as analog input auto scan function, and global output enable switch, are implemented in software. Test results from hardware-in-the-loop simulator verify tolerance time for each error, as well as cause of fault, error reset conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.66-71
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• 2022

The insulator used for the transmission line is a device that is bonded with a cap, pin, ceramic, and cement to withstand insulation capacity and mechanical load. The insulator design can help to reduce the dispersion of the electric field; thus, the optimization of today's design, especially as demanded power grows, is critical. The designs of four manufacturers were used to perform a comparative analysis. Under dry circumstances of the new product, an electric field distribution study was done with no pollutants attached. Manufacturer D's design has the best voltage uniformity of 24.33% and the arc length of 500 mm or more. Manufacturer C's design has an equalizing voltage of more than 2% higher than that of other manufacturers. The importance of the design of the insulator and the number of connections according to the installation conditions is very efficient for transmission lines that will increase in the future.

• Applied Microscopy
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• v.45 no.4
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• pp.189-194
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• 2015

Backside Ar ion milling technique for the preparation of cross-sectional transmission electron microscopy (TEM) specimens, and backside-ion milling combined with focused ion beam (FIB) operation for electron holography were introduced in this paper. The backside Ar ion milling technique offers advantages in preparing cross-sectional specimens having thin, smooth and uniform surfaces with low surface damages. The back-side ion milling combined with the FIB technique could be used to observe the two-dimensional p-n junction profiles in semiconductors with the sample quality sufficient for an electron holography study. These techniques have useful applications for accurate TEM analysis of the microstructure of materials or electronic devices such as arrayed hole patterns, three-dimensional integrated circuits, and also relatively thick layers (> $1{\mu}m$).

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.5
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• pp.1051-1057
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• 2001

In this paper, we deal with three types of modelling method for the analysis of galloping in power transmission line (PTL). The single mass model is obtained under linearization method and it is applied into f-order model. On these models, the nature frequencies of PTL are obtained and it makes an effects on the galloping directly. In simulation, we verify that the maximum magnitude of nature frequency depends on the galloping distance of PTL. Also from the analysis of frequency response, a few of reduction method for galloping are introduced which is effected by distance of PTL, wind velocity and icing types.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.3
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• pp.255-261
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• 2007

By using numerical analysis methods, through transmission type pulsed eddy current (PEC) testing is modeled and PEC signal responses due to varying material conductivity, permeability, thickness, lift-off and pulse width are investigated. Results show that the peak amplitude of PEC signal gets reduced and the time to reach the peak amplitude is increased as the material conductivity, permeability, and specimen thickness increase. Also, they indicate that the pulse width needs to be shorter when evaluating the material conductivity and the plate thickness using the peak amplitude, and when the pulse width is long, the peak time is found to be more useful. Other results related to lift-off variation are reported as well.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.824-828
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• 2011

Transmission line analysis of the surface a cumulation layer in injection-enhanced gate transistor (IEGT) is presented for the first time, based on per-unit-length resistance and conductance of the surface layer beneath the gate of IEGT. Lateral electric field on the accumulation layer surface, as well as the electron current injected into the accumulation layer, is governed by the well-known wave equation, and decreases as an exponential function of the lateral distance from the cathode. Unit-length resistance and conductance of the layer are expressed in terms of the device parameters and the applied gate voltage. Results obtained from the experiments are consistent with the numerical simulations.