• Journal of Electrical Engineering and Technology
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• v.3 no.2
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• pp.213-217
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• 2008

The flux-lock type superconducting fault current limiter(SFCL) can apply the magnetic field into the high-$T_C$ superconducting(HTSC) element by adopting the magnetic field coil in its third winding. To apply the magnetic field into the HTSC element effectively, the capacitor for LC resonance is connected in series with the magnetic field coil. However, the current waveform of third winding for the application of the magnetic field is affected by the LC resonance condition for the frequency of the source voltage and can affect the waveform of the limited fault current. In this paper, the current waveform of the third winding in the flux-lock type SFCL according to LC resonance condition during a fault period was analyzed. From the differential equation for its electrical circuit, the current equation of the third winding was derived and described with the natural frequency and the damping ratio as design parameters. Through the analysis according to the design parameters of the third winding, the waveform of the limited fault current was confirmed to be influenced by the current waveform of the third winding and the design condition for the stable fault current limiting operation of this SFCL was obtained.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.49-51
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• 2009

This paper deals with the analysis on eddy current losses for cylindrical linear oscillatory actuator (LOA) with Halbach array mover according to voltage waveform. This paper presents analytical procedures for calculation of eddy current losses using Poynting theorem. On the basis of the magnetic vector potential and a two-dimensional (2-d) cylindrical coordinate system, this paper derived analytical solutions of eddy current tosses using phase current analysis. The eddy current losses of each harmonic obtained by fast Fourier transform (FFT) analysis of phase current are compared with results obtained from finite-element method (FEM). Particularly, this paper shows that the eddy current losses of cylindrical LOA according to square voltage waveform are more significant than those according to sinusoidal voltage waveform.

• Journal of Welding and Joining
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• v.33 no.4
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• pp.24-29
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• 2015

The current waveform was analysed to monitor the weld quality in real time process. The acquired current waveform was discretely analysed for the top and bottom limits of peaks as well as the pulse frequency measurement. Fast Fourier Transform was implemented in the program to monitor the pulse frequency in real time. The developed algorithm or program was tested for the validation purpose. The cross-section of weld profile was compared to the current waveform profile to correlate the monitored signal and the actual parts. Pulse frequency was also used as auxiliary tool for the quality monitoring. Based on the results, it was possible to evaluate the quality of welding by measure the current waveform profile and frequency measurement.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.1
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• pp.120-126
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• 2013

The main aim of this paper is to expound high-efficiency operation of Switched Reluctance Generator (SRG) based on the current waveform. For this purpose, theoretical analysis of the copper loss and iron loss of the system is done first. Then, necessary simulation is done to find the variation trend of the copper loss and iron loss with the variation of the current waveform at the same output power. Finally, the best current waveform which can make the system operate with high efficiency is obtained by considering the influence of these two kinds of loss. In order to verity the simulation results, the experimental platform of DC motor-SRG is built and the modified angle position control (APC) method which can specify the current shape optionally is presented. By comparing the system efficiency at the three kinds of typical current waveform, the correctness and feasibility of the theory is verified. The proposed method is simple, reliable, and easy to achieve.

• Journal of Welding and Joining
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• v.32 no.2
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• pp.70-75
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• 2014

In automotive industry, applying of Mg alloy to autobody has been issued recently as a light metal. But poor resistance spot weldability of Mg alloy is blocking commercialization. So studies on improving resistance spot weldability of Mg alloy is increasing continuously. For reduce loss of heat input during welding, inverter DC power source is considered because of short rise time to target welding current. But rapid rising of welding current can increase temperature rapidly in nugget and oxide film between electrode and base metal, and that causes generating expulsion on low welding current range. In this study, for increase optimum welding current range and prevent generating expulsion, applicate various types of welding current waveform controls during resistance spot welding. For analysis effects of each current waveform control, acceptable welding current regions according to electrode force and welding time is determined and lobe diagram is derived. In result, pre heat is proposed as optimum type of welding current waveform control.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.63-68
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• 2013

This paper is aimed to make an analysis on characteristics of the parallel arc waveform and RMS of current at the electrical tracking state by conductive powder. In order to achieve the goal in this paper, field state investigation at metal processing companies in Chung-Nam province area was conducted. With the field state investigation, conductive powder were collected from metal processing companies. By experiment on electrical connector(breaker, connector) over which the conductive powder were scattered, arc waveform and RMS of current were measured. The measured waveform and RMS(root-mean-square) of current were analyzed to describe characteristics and patterns of electrical arc by the conductive powder. It was proved that conductive powder on electrical connector can flow electrical current enough to make electrical fire with high thermal energy. Also the change of sine waveform and RMS of current can be used to find out relationship between electrical fire and fault signal by conductive powder. The results obtained in this paper will be very helpful for the prevention of electrical fires occurred at the metal processing companies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.1
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• pp.155-161
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• 2005

Nonlinear electronic loads used at office buildings distort the voltage and current waveform that cause the overheating of transformer losses, ELB(Electrical Leakage Breaker) tripping, and so on. This paper analyzed waveform distortion characteristics at several once buildings by comparing with magnitude of voltage and current harmonics, crest factor of voltage and current, phase voltage and current unbalance. As a consequence, severe current waveform distortion in phase and neutral line by harmonics and high current unbalance rates by unbalanced using of single loads among the three phases are investigated. The results of the study can be used in making decisions regarding reasonable and economical operating of loads at office buildings.

• Journal of the Korean Society of Mechanical Technology
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• v.20 no.6
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• pp.783-789
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• 2018

This paper investigates the relationship of voltage and current waveform between normal piezo injector and deterioration abnormal piezo injector. The experimental methods using Pico oscilloscope and GDS scan tool are employed to measure current and voltage waveform and fuel pressure of piezo injector. The experiment is carried out during no-load condition. A summary of the important results are as follows. 1) In case of normal injector, the fluctuation of duration time of piezo injector was linearly and regularly decreased with increasing engine speed, but the that of deterioration piezo injector was irregularly decreased with increasing engine speed. 2) In main injection, the peak value of the current waveform of abnormal injector was larger than that of normal injector, the duration time of deteriorated abnormal injector was less than that of normal injector at 800rpm and 1500rpm, but the duration time of deteriorated abnormal injector was larger than that of normal injector at 2000rpm and 3000rpm. This irregularity appears to be caused by the deterioration of the injector.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.7
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• pp.127-133
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• 2001

The effects of triangular and rectangular discharge current waveforms on anode erosion in wire electric discharge machining is investigated based on heat transfer analysis of half-space subject to time and space-dependent heat flux. The thermal load on the anode is simulated by a hear flux that is calculated from time-dependent discharge channel radius and energy. Evolution of the melting front during discharge, the molten volume at the experimental result for qualitative verification of the analysis. It is demonstrated that the triangular current waveform is more efficient in eroding the anode than the rectangular one.

• The Journal of Information Technology
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• v.8 no.4
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• pp.1-7
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• 2005

Investigations of high frequency current transformer(HF-CT) waveform characteristics of the surface leakage on kaolin polluted EPDM polymer insulators have been performed. This work is part of a program aimed at examining the potential for HF-CT waveform characteristics analysis to provide information about the environment contaminants and environment condition of polymer insulators. The investigation reported examined the HF-CT waveform characteristics at high frequencies. The use of high frequency measurements for on-line applications reduces electrical inference. This work was peformed utilizing HF-CT to monitor of surface polluted discharge. It was found that HF-CT waveform frequency spectrum, magnitude depend on importantly the duration of the surface discharge activity.