• Title, Summary, Keyword: Current

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The Effect of Direct and Variable Current on Current Efficiency of Copper Anode (조동의 전류효율에 미치는 직류 및 가변전류의 영향)

  • Ahan, Sung-Chen;Lee, Sang-Mun;Kim, Yong-Hwan;Chung, Won-Sub
    • Journal of the Korean institute of surface engineering
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    • v.39 no.5
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    • pp.223-228
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    • 2006
  • The current efficiency of copper anode containing impurities in copper sulfate solution for electrorefining was studied at various current type such as direct current, variable current and periodic reverse current. The passivity behavior was investigated by galvanostatic technique. The results obtained were that current efficiency of variable current was higher than those of direct current and periodic reverse current. The increased current efficiency could be explained by the formation of slime structure with lower average resistance due to variable current. The frequency of various factors in variable current condition has a greatest effect on current efficiency. It appeared that frequency increased current efficiency when increased from 1 to 4, but further increases did not have an effect.

Accuracy Enhancement Technique in the Current-Attenuator Circuit (전류 감쇠 조정 회로에서의 정밀도 향상 기술)

  • Kim, Seong-Kweon
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.8
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    • pp.116-121
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    • 2005
  • To realize the tap coefficient of a finite impulse response(FIR) filter or the twiddle factor of a fast Fourier transform(FFT) using a current-mode analog circuit, a high accurate current-attenuator circuit is needed This paper introduces an accuracy enhancement technique in the current-mode signal processing. First of all, the DC of set-current error in a conventional current-attenuator using a gate-ratioed orient mirror circuit is analyzed and then, the current-attenuator circuit with a negligibly small DC offset-current error is introduced. The circuit consists of N-output current mirrors connected in parallel with me another. The output current of the circuit is attenuated to 1/N of the input current. On the basis of the Kirchhoff current law, the current scale ratio is determined simply by the number of the current mirrors in the N-current mirrors connected in parallel. In the proposed current-attenuator circuit the scale accuracy is limited by the ac gain error of the current mirror. Considering that a current mirror has a negligibly small ac gain error, the attainable maximum scale accuracy is theoretically -80[dB] to the input current.

Characteristics for Current and Power of Induction Motor by Load Variation (부하변동에 따른 유도전동기 전류와 전력 특성)

  • Kim, Jong-Gyeum
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.25 no.8
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    • pp.82-87
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    • 2011
  • Induction motor is most widely used as the driving power in the industrial site. Induction motor current is composed of two parts, magnetizing current and load current. Load current uses energy what is doing the work. Load current varies with load variance but magnetizing current is constant, regardless of load variation. Magnetizing current needs for establishing the rotating magnetic field of induction motor and lags behind the voltage. Generally capacitor is used for power-factor compensation of inductive load. Self-excitation occurs when the capacitive reactive current from the capacitor is greater than the magnetizing current of the induction motor. When this occurs, excessive voltages can result on the terminals of the motor. This excessive voltage can cause insulation degradation and ultimately result in motor insulation failure. In this paper, we analyzed that how the magnetizing current and condenser current is operating at the allowable limit by the load variation. Condenser current is below allowable limit of magnetizing current but magnetizing current is above allowable limit at the lower load operation condition.

the Active Current Bias Control using Flyback Converter (Flyback Converter를 이용한 Active Current Bias 제어)

  • Hwang Seon-Nam;Lim Sung-Kyoo;Lee Jun-Young
    • Proceedings of the KIPE Conference
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    • pp.84-87
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    • 2006
  • 본 연구는 Current Mirror에 있어서 Active Current Bias에 관하여 기술하였다. Current mirror에서 Active Current Bias를 걸어주는 보편적인 방법은 Current Bias단에 저항을 연결하여 저항값을 조절함으로 해서 Current를 제어하는 방법을 사용한다. Reference 전류를 제어하는데 있어 새로이 제안하는 것은 Flyback Converter를 이용하여 Acitve Current Bias를 제어 하려 한다. 트랜지스터를 이용하여 Current Mirror Circuit를 구성하고 Current Bias 측에 Flyback Converter Circuit을 연결한다. Flyback Converter의 PWM의 Duty Ratio를 조절함으로 해서 전류를 제어하는 특징을 이용하여 Active Current Bias를 제어한다.

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A Phase Current Reconstruction Technique Using a Single Current Sensor for Interleaved Three-phase Bidirectional Converters

  • Lee, Young-Jin;Cho, Younghoon;Choe, Gyu-Ha
    • Journal of Electrical Engineering and Technology
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    • v.11 no.4
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    • pp.905-914
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    • 2016
  • This paper proposes a new phase current reconstruction technique for interleaved three-phase bidirectional dc-dc converters using a single current sensor. In the proposed current reconstruction algorithm, a single current sensor is employed at the dc-link, and the dc-link current information is sampled at either the peak or valley point of the pulse-width modulation (PWM) carriers regularly. From the obtained current information, all phase currents are reconstructed in a single PWM cycle. After that, the digital current controller is applied to achieve current balancing in each phase. Compare to the previous multiple current sensor method, the proposed strategy reduces the number of the current sensors in the interleaved three-phase bidirectional converter as well as reducing potential current sensing error caused by non-ideal characteristics of the multiple current sensors. The effectiveness of the proposed method is verified from the experiments based on a 3kW three-phase bidirectional converter prototype for the automotive battery charging application.

Accuracy of Current Delivery System in Current Source Data-Driver IC for AM-OLED

  • Hattori, Reiji
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.4 no.4
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    • pp.269-274
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    • 2004
  • Current delivery system, in which the analog current produced by a unique DAC circuit is stored into a current-memory circuit and delivered in a time-divided sequence, shows variation of output current as low as 4% in a current source data-driver IC for AM-OLED driven by a current-programmed method without any fuse repairing after fabrication. This driver IC has 54 outputs and can sink constant current as low as 3 ${\mu}A$ with 6-bit analog levels. Such a low current level without variation can hardly be obtained by an ordinary MOS transistor because the current level is in the sub-threshold region and changes exponentially with threshold voltage variation. Thus we adopted a current mirror circuit composed of bipolar transistors to supply well-controlled current within a nano-ampere range.

Quench characteristics of HTS tapes applied over-current (과전류 인가 시 고온초전도 선재의 ?치 특성)

  • 임성우;최용선;황시돌;한병성
    • Progress in Superconductivity
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    • v.4 no.2
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    • pp.184-188
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    • 2003
  • Voltage-current characteristics of High Temperature Superconductor(HTS) tapes after applying the current beyond their critical current was investigated. When over-current is applied, the current begins to flow through the metal sheath instead of superconductor. The HTS tapes quenched were analyzed using V-I curve with various magnitudes of current. Two kinds of tapes were compared with each other to examine the influence of critical current on quench development. As a result, it was found that the resistance of superconductors and joule heat due to the over-current affect current distribution in HTS tapes. Critical current of HTS tapes was considered as a main factor deciding over-current characteristics.

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Development and Safety Estimation of Resistive Leakage Current(Igr) of Detection Outlet (저항성 누설전류(Igr) 검출 콘센트의 개발 및 안전성 평가)

  • Kim, Chang-Soung;Hanh, Song-Yop;Choi, Chung-Seog
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.58 no.2
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    • pp.221-226
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    • 2009
  • In this paper, we analyzed form of flowing leakage current in electrical installation. Leakage current ($I_g$) is consisted of resistive leakage current($I_{gr}$), capacitive leakage current($I_{gc}$), and inductive leakage current($I_{gl}$). Resistive leakage current($I_{gr}$) is big occasion than capacitive leakage current($I_{gc}$) in system, Residual Current Protective Device(RCD) detects correctly leakage current. But,$I_{gc}$ is big occasion than $I_{gr}$, RCD is malfunctioned It is resistance to lead to electric fire in electrical device. We manufactured outlet that resistive leakage current detecting circuit is had. Manufactured outlet displayed performance exactly in leakage current of 5 mA Therefore, this product estimates that contribute on electric fire courtesy call.

Unsteady-state analysis of current lead for DC Reactor of 6.6kV-200A superconductor current limiter (6.6kV-200A급 초전도 한류기 DC Reactor용 전류도입선의 비정상상태 해석)

  • 김형진;권기범;정은수;장호명
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • pp.182-185
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    • 2003
  • Temperature distribution and cooling load in binary current lead are analized, occurring fault current at DC Reactor type superconductor fault current limiter. It is assumed that Normal operating current is 300 A and fault current is 3000 A. Unsteady-state temperature distribution and cooling load of brass current lead optimized for 300 A and 1000 A are calculated by numerical method with TDMA. In the result of calculation, temperature increase in the brass current lead optimized for 300 A is higher than that in the brass current lead optimized for 1000 A, but the temperature increase in the brass current lead optimized for 300 A is not serious. Moreover, increase of cooling load in the brass current lead optimized for 300 A is higher than that in the brass current lead optimized for 1000 A, but normal cooling load in the brass current lead optimized for 300 A is lower than that in the brass current lead optimized for 1000 A. Therefore, designing current lead in superconductor fault current limiter had better to optimize for normal operating current.

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Compensating algorithm for the secondary current of a measurement type CT considering the secondary voltage-core loss current curve and the flux linkage-magnetizing current curve (2차 전압-철손 전류 곡선과 자속-자화 전류 곡선을 고려한 측정용 변류기 2차 전류 보상 알고리즘)

  • Kang, Yong-Cheol;Zheng, Tai-Ying;Jang, Sung-Il;Kim, Yong-Gyun
    • Proceedings of the KIEE Conference
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    • pp.65-66
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    • 2008
  • This paper proposes a compensating algorithm for the secondary current of the measurement current transformer (CT) that removes the effects of the hysteresis characteristics of the iron-core. The exciting current resulting from the hysteresis characteristics of the core causes an error between the primary current and the secondary current of the CT. The proposed algorithm decomposes the exciting current into the magnetizing current and the core loss current and each of them is estimated. The core loss current is calculated from the secondary voltage and the secondary voltage-core loss current curve. The core flux linkage is calculated and then inserted into the flux-current curve to estimate the magnetizing current. The exciting current at every sampling interval is obtained by summing the core-loss and magnetizing currents and then added to the measured current to compensate the secondary current. The performance of the proposed algorithm is validated under various conditions using EMTP generated data. The test results of the real CT were also included. The results indicate that the proposed algorithm can improve the accuracy of the measurement CT significantly, and thus reduce the size and the cost of the CT.

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