• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1169-1171
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• 2001

Synchronous reluctance motors(SynRM) for the application such as an electric vehicle, compressor drives of air conditioner and machine tool spindle drives require a wide field-weakening speed range. In order to improve the efficiency performance in such applications, this paper has examined the loss and the efficiency characteristics of SynRM mainly in the field-weakening speed region over the base speed. The control strategy in order to offer a efficiency optimization operation is shown and the copper and iron losses driven the equivalent circuit model of the machine is minimized. The usefulness of the proposed efficiency optimization control is verified through the SynRM durve system.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.263-269
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• 2018

In this study, a selective inverter operation between a 2-level voltage source converter (VSC) and a 3-level T-type VSC (3LT VSC) is proposed to improve the efficiency of a 3LT VSC. The 3LT VSC topology, except for its neutral-point switches, has similar operations as that of the 2-level VSC. If an operation mode is changed according to efficiency, the efficiency can be improved because efficiencies of each methods are depending on current and MI (Modulation Index). The proposed method calculates the power losses of the two topologies and operates as the having lower losses. To calculate the losses, the switching and conduction losses based on the operation mode of each topology were analyzed. The controller determined the operation mode of the 2- or 3-level VSC based on the power loss calculated during every cycle. The validity of the proposed control scheme was investigated through simulation and experiments. The waveform and average efficiency of each method were compared.

• Journal of Magnetics
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• v.20 no.1
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• pp.57-61
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• 2015

In this paper wireless power transmission system based on magnetic resonance coupling circuit was carried out. With the research objectives based on the mutual coupling model, mathematical expressions of optimal coupling coefficients are examined. Equivalent circuit parameters are calculated by Maxwell software, and the equivalent circuit was solved by Matlab software. The power transfer efficiency of the system was derived by using the electrical parameters of the equivalent circuit. System efficiency was analyzed depending on the different air gap values for various characteristic impedances. Hence, magnetic resonance coupling involves creating a resonance and transferring the power without radiating electromagnetic waves. As the air gap between the coils increased the coupling between the coils were weakened. The impedance of circuit varied as the air gap changed, affecting the power transfer efficiency.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.295-299
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• 2018

In this work, we conducted a study on cell strings of high efficiency and high power solar cell modules via simulation. In contrast to the conventional module manufacturing method, the simulation was performed by connecting cutting cells divided into four parts from 6-in size using the electrically conductive adhesive (ECA). The resistance of the ECA added in series connection was extracted using an experimental method. This resistance was found to be $3m{\Omega}$. Based on this simulation, we verified the change in efficiency of the string as a function of the number of cutting cell connections. Consequently, the cutting cell efficiency of the first 20.08% was significantly increased to 20.63% until the fifth connection; however, for further connections, it was confirmed that the efficiency was saturated to 20.8%. Connecting cutting cells using ECA improves the efficiency of the string; therefore, it is expected that it will be possible to fabricate modules with high efficiency and high power.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.424-429
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• 2003

A reciprocating compressor with a rotary motor used in a refrigerator has low efficiency, because it has the large mechanical losses due to the crank mechanism. The linear compressor which has the free piston driven by a linear motor, was developed to increase the efficiency of compressor by reducing mechanical losses. The TRIAC has been widely used for controlling the piston, because it has simple structure. However, as it is able to control only stator voltage, it is very difficult to obtain good efficiency. Recently, PWM inverter which is able to control the voltage as well as the frequency, is applied to linear compressor drive system to overcome above problem. In this paper, the variations for efficiency and power factor of linear compressor are investigated by changing both the mechanical resonant frequency and electrical resonant frequency of linear compressor, and also the inverter frequency The optimum relationships between both resonant frequencies and the inverter frequency is derived in order to obtain the maximum efficiency and also good power factor.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.563-569
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• 2015

For some low-frequency applications such as power-related circuits, NEM relays have been known to show better performance than MOSFETs. For example, in a step-down charge pump circuit, the NEM relays showed much smaller layout area and better energy efficiency than MOSFETs. However, severe process variations of NEM relays hinder them from being widely used in various low-frequency applications. To mitigate the process-variation problems of NEM relays, in this paper, a new NEM-relay charge pump circuit with the self-adjustment is proposed. By self-adjusting a pulse amplitude voltage according to process variations, the power consumption can be saved by 4.6%, compared to the conventional scheme without the self-adjustment. This power saving can also be helpful in improving the power efficiency of the proposed scheme. From the circuit simulation of NEM-relay charge pump circuit, the efficiency of the proposed scheme is improved better by 4.1% than the conventional.

• Journal of Electrical Engineering and Technology
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• v.11 no.5
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• pp.1063-1069
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• 2016

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.49-51
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• 2002

This paper deals with the efficiency evaluations in a synchronous reluctance motor (SynRM) using a coupled transient finite element method (FEM) and Preisach modeling, which is Presented to analyze the characteristics under the effect of saturation and hysteresis loss. The focus of this paper is the efficiency evaluation relative to hysteresis loss, copper loss, etc. on the basis of speed, load condition in a SynRM. Computer simulation and experimental result for the efficiency using dynamometer show the propriety of the proposed method.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.393-396
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• 2001

According to the development of power electronic element(GTO, IGBT) and material for electrical machines(permanent magnet, super conductor), the technology for electrical machines is nowaday rapidly developing. Here with, a novel electrical machine, based on the new conception of transverse flux configuration leads to a considerable Increase in power density and enables simultaneously high efficiency. The transverse flux machine with PM excitation will be applied to gearless direct drives for railway traction system and magnetic levitation system. The designed and measured performance of transverse machine for railway traction system and magnetic levitation system revealed a great potential of system improvements to reduce linear motor mass and increase efficiency.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1049-1050
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• 2006

This paper is proposed to a novel DC-DC converter operated high efficiency for loss-less snubber capacitor. The general converters of high efficiency is made that the power loss of the used switching devices is minimized. To achieve the soft switching operation of the used control switches, the proposed converter is constructed by using a loss-less snubber capacitor. The proposed 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 converter is high. The soft switching operation of the proposed converter is verified by digital simulation and experimental results.