• 한국신뢰성학회지:신뢰성응용연구
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• 제17권1호
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• pp.22-27
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• 2017

Purpose: The purpose of this study is to estimate the life time of OLED TV panel through electric current ADT(Accelerated Degradation Test). Methods: We performed accelerated degradation test for OLED TV Panel at the room temperature to avoid high temperature impact on the luminance. Results: we got more accurately the life time of the OLED TV when we applied ADT without temperature factor than including both current and temperature. Conclusion: Until now, the ADT of the OLED TV has been conducted with temperature and current at the same time for reducing test time and costs. We estimate incorrect life time when the temperature is adopted as an accelerated factor. Due to the high temperature impact on the luminance of the OLED TV panel. So as to solve this problem, we discard temperature and use electric current only.

• Journal of Chest Surgery
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• 제22권4호
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• pp.548-561
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• 1989

In single atrial cells isolated from the rabbit the properties of inward current of Na-Ca exchange were investigated using the whole cell voltage clamp technique. The current was recorded during repolarization following brief 2 ms depolarizing pulse to +40 mV from a holding potential of * 70 mV. Followings are the results obtained: 1. When stimulated every 30 seconds, the inward currents were activated and reached peak values 6-12 ms after the beginning of depolarizing pulse. The mean current amplitude was 342 pA/cell. 2. The current decayed spontaneously from the peak activation and the time course of the relaxation showed two different phases fast and slow phase. The time constants were 10-18 ms and 60-140 ms, respectively. 3. The recovery of inward current was tested by paired pulse of various intervals. The peak current recovered exponentially with time constant of 140 ms and 1 p M isoprenaline accelerated the recovery process. 4. Relaxation time course was also affected by pulse interval and time constant of the fast phase was reduced almost linearly according to the decrease of pulse interval between 30 sec and 1 sec. 5. The peak activation was increased in magnitude by long prepulse stimulation, 5 p M Bay K, 1 p M isoprenaline or internal and external application of c-AMP. 6. The relaxation time constant of the fast phase was prolonged by 5 p M Bay K or c-AMP, and shortened by isoprenaline. However the time course of the slow relaxation phase was not so much changed. From the above results, it could be concluded that increase of the calcium current by Bay K or c-AMP results in the potentiation and prolongation of intracellular calcium transient, and the facilitation of Ca uptake by SR might be a mechanism of shortening the time constant of current relaxation by short interval stimulation or isoprenaline.

• 전력전자학회논문지
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• 제20권3호
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• pp.201-208
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• 2015

The effects of dead-time and offset error, which cause output current distortion in single-phase grid-connected inverters are investigated this paper. Offset error is typically generated by measuring phase current, including the voltage unbalance of analog devices and non-ideal characteristics in current measurement paths. Dead-time inevitably occurs during generation of the gate signal for controlling power semiconductor switches. Hence, the performance of the grid-connected inverter is significantly degraded because of the current ripples. The current and voltage, including ripple components on the synchronous reference frame and stationary reference frame, are analyzed in detail. An algorithm, which has the proportional resonant controller, is also proposed to reduce current ripple components in the synchronous PI current regulator. As a result, computational complexity of the proposed algorithm is greatly simplified, and the magnitude of the current ripples is significantly decreased. The simulation and experimental results are presented to verify the usefulness of the proposed current ripple reduction algorithm.

• 전기의세계
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• 제27권5호
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• pp.69-75
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• 1978

3 phase induction motor applied in the method of connecting it directly across the line needs large current when it starts. At that time, leakage magnetic pathes of interior of the motor are severely saturated and leakage reactances are decreased because of saturation. Consequently, increased current and raised powerfactor yield increase of starting torque. The author, noticing those phenomena, derived experimentally the raion of decreasing leakage reactance from the fact that when voltage applied to motor is increased under locked condition the magnitude of current and phase angle are varied, and determined tha equations of starting current and starting torque, considering the decrease of leakage reactance by the large starting current. The author calculated the characteristics of Current-Time and Speed-Time with the determined equation at specific load conditions, and compared the values obtained from above calculations with those from circle diagram's method and the practically recorded values at same load conditions. Therefore, the authos got a confidience that the results of the derived theory coincide with the practically measured values more well than circle diagram's results and circle diagram's equation should be modified in order to analize the starting status of a induction motor.

• 한국해양공학회지
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• 제18권5호
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• pp.22-28
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• 2004

This study constructed a 3D real-time numerical model that predicts the water quality and movement characteristics of the inner bay, considering the characteristics of the wind-driven current and density current in estuaries, generated by the river discharge from the Hyeong-san river and oceanic water of the Eastern sea. The numerical model successfully calculated the seawater circulation current of Yeong-il Bay, using the input conditions oj the real-time tidal current, river discharge, and weather conditions during March 2001. This study also observed the wind-driven current and density current in estuaries that are effected by the seawater circulation pattern of the inner bay. We investigated and analyzed each impact factor, and its relationship to the water quality of Yeong-il bay.

• Journal of Welding and Joining
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• 제21권1호
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• pp.48-53
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• 2003

The object of this study is to examine the effect of short circuit time ratio (SCTR) and current rise delay time (Td) on the spatter generation at low and medium current range in $CO_2$ welding. The spatter was evaluated by the weight generated in the welding of bead-on-plate for 30 seconds (3 times). Td was varied by order of 0, 0.4, 0.8 and 1.2 msec. At each Td, the short circuit time ratio was varied by the output voltage of the welding power source. In the low current range, it was found that the optimum SCTR was 20~25%, and the minimum spatter generation weight was obtained in the case of Td=0.4msec and SCTR=22% even though the remarkable difference was not showed by the application of Td. In the medium current range, it was confirmed that the arc was stable though the SCTR was increased from 20% to 40% by the control of current wave. Spatter generation weight depended on the variation of Td, and the lowest value of spatter generation weight occurred at Td=0.8~1.2msec.

• 제어로봇시스템학회논문지
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• 제9권12호
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• pp.1001-1008
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• 2003

A time-delay compensation method for vector control system is proposed that can compensate for voltage and current distortions resulting from a time delay in the overall system due to the low pass filter, hysteresis control inverter, microprocessor program computation time, and so on. The proposed scheme estimates the time delay using the difference between the Q-axis stator current command and the time-delayed actual Q-axis stator current in a synchronous reference frame, then compensates the time delay in the voltage and current using the angular displacement of a DQ transformation. Accordingly, the proposed scheme can accurately compensate for the time delay related to the overall system, thereby significantly improving the performance of the vector control system, as verified by simulation and experiment.

• 한국안전학회지
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• 제37권1호
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• pp.12-19
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• 2022

Circuit breakers are a crucial factor in ensuring the safety of a Direct Current (DC) grid. One type of DC circuit breaker, the Z-source DC circuit breaker (ZCB), uses a thyristor, which is a type of semiconductor switch. In the event of a fault in the circuit, the ZCB isolates the fault by generating a zero crossing current in the thyristor. The thyristor quickly and actively isolates the fault while generating a zero crossing current, but thyristor switch cannot control turn-off and the allowable current is lower than the current of the mechanical switch. Therefore, it is best to use a mechanical switch with a high allowable current capacity that is capable of on/off control. Due to the slow reaction time of mechanical switches, they may not isolate the fault during the zero crossing current time interval created by the existing circuit. In this case, the zero crossing current time can be increased by using the property that hinders the rapid change in the current of the inductor. This paper will explore whether adding system inductance to increase the zero crossing current time interval is a solution to this problem. The simulation of changing inductor and capacitor (LC) of the circuit is repeated to find an optimal change in the zero crossing current time according to the LC change and provides an inductor and capacitor range optimized for a specific load. The inductor and capacitor range are expected to provide optimization information in the form LC values for future applications of ZCB's using a mechanical switch.

• Journal of Welding and Joining
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• 제8권1호
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• pp.31-42
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• 1990

Arc must be stable during welding first of all other factors for obtaining sound weldment, especially in the automation of welding process. Arc stability is somewhat sophisticated phenomenon which is not clearly defined yet. In consumable electrode welding, the voltage and current variation due to metal transfer enables to assess arc stability. Recently, statistical analyses of the voltage and current waveform factors are performed to assess the degress of arc stability which is assessed and controlled by operator's own experience by now. But, considering the increasing need and the trend of automation of welding process, it is necessary to monitor arc stability in real-time. In this sutdy, the modified stability index composed of two voltage and current wvaeform factors (arc time and short circuit time) reduced from four factors (arc time, short circuit time, average arc current and average short circuit current) in Mita's index by the welding electrical circuit modeling is proposed and verified by experiments to be well estimating arc stability in the static sense. Also, the recursive calculation form estimating present arc stability in the dynamic sense is developed for real-time estimation. The results of applying the recursive index during welding show good estimation of arc stability in real-time. Therefore, the results of this study offers the mean for real-time control arc stability.

• 조명전기설비학회논문지
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• 제26권12호
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• pp.44-49
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• 2012

The earth leakage circuit-breakers installed to protect the human body against electrical shock have conventionally had a sensitivity current of 30 mA and an operating time of 30 ms or less. No reviews are found, however, on the operating time of the current conducting through the human body due to the electrical shock or ground fault. This paper measures the trip-operating time against the earth leakage under the condition of increased current as well as under the condition of rated sensitivity current of the earth leakage circuit-breakers. Further measurement with a prototype model showed an improved operating time of 16 ms or less under the condition of rated sensitivity current. It is expected that development of circuit-breakers with higher safety is possible if the performance of the electronic circuit can be improved.