• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.7-10
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• 2001

This paper provides a solution for the problem of efficiency decrease caused by load variation. A novel control scheme of tracking the PT's operation frequency for the maximum efficiency is proposed. As a result, a high efficiency over $80\%$ has been achieved even under the output-current decrease down to $10\%$ of the full load current.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.4
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• pp.586-593
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• 1994

This paper suggests the algorithm for on-line efficiency control of permancent magnet synchronous motors driving the electric vehicles. The existance of unigue d-axis current is verified, which generates the maximum efficiency at operating points of motor. Using the Fibonacci search method, d-axis current converges to the minimization of inverter input power, and to prevent the variation of motor speed in process of the efficiency control, the voltage decoupled control strategy is introduced. Through the experiments, the effects of an efficiency control algorithm are verified.

• Journal of Environmental Health Sciences
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• v.23 no.1
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• pp.43-49
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• 1997

This study was aimed to estimate removal efficiency(%) of BER(Biofilm-Electrode Reactor) and A.S(Activated Sludge) treatments. When were analyzed COD$_{Cr}$, NH$_3$-N and T-P by current density and reaction time, the results were as follows : 1) In BER treatment, the removal efficiency of COD$_{Cr}$ in domestic wastewater was 79-86% when current density was 2.39 mA/dm$2$(15mA)-3.98 mA/dm$^2$(25mA) and reaction time was 48 hr. 2) Removal efficiency of NH$_3$-N was 71-73% when current density was 2.39-3.98 mA/dm$^2$ and reaction time 48 hr. 3) When the reaction time was 48 hr removal efficiency(%) of BER treatment for COD$_{Cr}$, NH$_3$-N and T-P were more excellent than A.S. treatment. And then we prospect that was because activated microorganism colonies attached in biofilm on surface of electrode pannel. Therefore, In order to derive BER treatment efficiency(%) should establish optimum conditions of pH, temp., reaction time, current density and biochemical and electrochemical states.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.355-358
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• 2009

This paper proposes efficiency optimization control of IPMSM drive using multi hybrid fuzzy controller(HFC). The design of the speed controller based on fuzzy-neural network that is implemented using fuzzy control and neural network. The design of the current based on HFC using model reference and the estimation of the speed based on neural network using ANN controller. In order to maximize the efficiency in such applications, this paper proposes the optimal control method of the armature current. The controllable electrical loss which consists of the copper loss and the iron loss can be minimized by the optimal control of the armature current. The minimization of loss is possible to realize efficiency optimization control for the proposed IPMSM The optimal current can be decided according to the operating speed and the load conditions. This paper considers the design and implementation of novel technique of high performance speed control for IPMSM using multi HFC. Also, this paper proposes speed control of IPMSM using HFC1, current control of HFC2-HFC3 and estimation of speed using ANN controller. The proposed control algorithm is applied to IPMSM drive system controlled HFC, the operating characteristics controlled by efficiency optimization control are examined in detail.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.711-715
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• 2007

Properties of organic light-emitting diodes (OLEDs) with aluminum-doped zinc oxide (ZnO:Al) anodes showed different behaviors from OLEDs with indium tin oxide (ITO) anodes according to driving conditions. OLEDs with ITO anodes gave higher current density and luminance in lower voltage region and better EL and power efficiency under lower current density conditions, However, OLEDs with ZnO:Al anodes gave higher current density and luminance in higher voltage region over about 8V and better EL and power efficiency under higher current density over $200mA/cm^2$. These seemed to be due to the differences in conduction properties of semiconducting ZnO:Al and metallic ITO. OLEDs with ZnO:Al anodes showed nearly saturated efficiency under high current driving conditions compared with those of OLEDs with ITO anodes. This meant better charge balance in OLEDs with ZnO:Al anodes. These properties of OLEDs with ZnO:Al anodes are useful in making bright display devices with efficiency.

• Progress in Superconductivity
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• v.14 no.2
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• pp.96-98
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• 2012

Bias current dependence of a superconducting strip photon detector is studied in the wavelength range of 405 to 1310 nm. The detector is made of an $MgB_2$ meander pattern with the line width of 135 nm and thickness of 10 nm. At 1310 nm, the detection efficiency exponentially decreases as the bias current decreases. While at 405 nm, the detection efficiency almost saturates in the high bias current region. These features suggest that the intrinsic detection efficiency of the $MgB_2$ detector is high at 405 nm.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.3
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• pp.280-289
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• 2015

A high-efficiency full-bridge DC-DC converter with a current-doubler rectifier and an asymmetric pulse-width modulation is proposed. Through the asymmetric pulse-width modulation, the proposed converter achieves zero-voltage switching of power switches without the circulating currents. The proposed converter reduces the output current ripple through the current-doubler rectifier. A control strategy is suggested for the proposed converter to charge battery banks. A constant current and constant voltage charging is performed. The proposed converter achieved a higher efficiency compared with the conventional full-bridge DC-DC converter with a phase-shift modulation. The performance of the proposed converter is evaluated by the experimental results for a 1.0 kW prototype circuit.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12S
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• pp.1268-1272
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• 2003

In order to enhance current Injection efficiency of Y-groove inner strife(VIS) quantum wire lasers, three different current configurations, n-blocking on p-substrate(VIPS), p-n-p-n blocking on n-substrate(VI(PN)nS), p-blocking on n-substrate(VINS) have been designed and fabricated. Among them VIPS laser showed the most stable characteristics of lasing up to 5 mW/facet, a threshold current of 39.9 mA at 818 nm, and an external differential quantum efficiency of 24 %/facet. The current tuning rate was almost linear 0.031 nm/mA, and the temperature tuning rate was measured to be 0.14 nm/$^{\circ}C$.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.9
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• pp.431-436
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• 2005

This paper studies a novel boost DC-DC converter operated high efficiency for discontinuous current mode (DCM) control. The converter worked in DCM eliminates the complicated circuit control requirement, reduces a number of components, and reduces the used reactive components size. In the general DCM converter, the switching devices are turned-on the zero current switching (ZCS), and the switching devices must be switched-off at a maximum reactor current. To achieve the zero voltage switching (ZVS) at the switching turn-off, the proposed converter is constructed by using a new loss-less snubber circuit. Soft-switched operation of the proposed boost converter is verified by digital simulation and experimental results. A new boost converter achieves the soft-switching for all switching devices without increasing their voltage and current stresses. The result is that the switching loss is very low and the efficiency of boost DC-DC converter is high.

• Journal of the Korean institute of surface engineering
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• v.37 no.1
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• pp.13-21
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• 2004

The deposition rate, the current efficiency and surface morphology of trivalent Cr deposits were investigated according to additives in sulfate bath and current density. The deposition rate of the Cr deposits plated from the formic acid complexed bath was noticeably higher than that of the glycine complexed bath. The current efficiency of the deposition from formic acid bath was higher than that of the glycine bath and increased with current density in the range of 20-50 A/d$\m^2$. The current efficiency of the deposition from the formic acid bath with boric acid buffer was higher than that of the bath with aluminum sulfate or boric acid-aluminum sulfate buffers. The nodular crystallite size of the Cr deposits increased with current density and the uniform and crack-free growth of the deposits for the aluminum sulfate was observed compared to the other buffers.