• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2685-2687
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• 1999

This paper is concerned on developing DC-DC converter. In contrast to resonant converter, this converter requires no external resonant elements and operates with constant switching frequency. In conventional PWM converter, two MOSFET switches of the converter are simultaneously turned on and turned off. In presented converter, to achieve Zero Voltage Switching, the two legs of the bridge are operated DC-DC converter is phase shifted. Phase shifted Full Bridge ZVS PWM Converter have an effect on the power system. Operation principle and features are illustrated by the experiment results from 50W, 250kHz with MOSFET switch.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2556-2558
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• 1999

We present voltage-source inverter for variable speed of washing machine. In the case of previous washing machines only on/off contol of motor was satisfied but these days the desire of customers moves to more silent and energy saving machine. Therefore many white goods manufacturers consider variable driving methods of motor. Nowadays variable speed Induction motors powered by inverters are becoming more and more popular. In this paper the principles of constant V/F control of Induction motor used in washing machine and space vector PWM technique are reviewd. Implementation issues such as command voltage generation, switching pattern determination, speed and power measurement are also presented. Experimental results are included in the end of the paper.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2168-2173
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• 2003

Pressure balancing valve is one of important control devices, which is fully automatic and no manual controls, regulating or adjustments are needed. It is typically used to maintain constant temperature of working fluid in power and chemical plants and domestic water supply systems. Pressure balancing valve is composed of body, cylinder and balancing piston. Therefore, the balancing piston shapes are important design parameters for a pressure balancing valve. In this study, numerical and experimental analyses are carried out with two different balancing piston shapes. Especially, the distribution of static pressure is investigated to calculate the flow coefficient($C_v$). The governing equations are derived from making using of three-dimensional Navier-Stokes equations with standard ${\kappa}-{\varepsilon}$ turbulence model and SIMPLE algorithm. Using commercial code, PHOEIC, the pressure and flow fields in pressure balancing valve are depicted.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.112-115
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• 1999

A new method to solve a Lyapunov equation for a discrete delay system is proposed. Using this method, a Lyapunov equation can be solved from a simple linear equation and N-th power of a constant matrix, where N is the state delay. Combining a Lyapunov equation and frequency domain stability, a new stability condition is proposed. The proposed stability condition ensures stability of a discrete state delay system whose state delay is not exactly known but only known to lie in a certain interval.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.4
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• pp.136-142
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• 1996

Automatic monitoring of cutting process is one of the most important technology in machining. AE sensing technology has been applied to monitoring process and proved to be effective in detecting tool abnor- malities such as tool wear and fracture. In this experimental study. AE signals were detected from the tool holder for continuous and interrupted cutting, which obtained from changing workpice material configuration, under control of constant cutting speed from CNC lathe. From statistical and frequency analysis, the AE signals were analyzed to obtaining the characteristics of continuous and interrupted cutting conditions and tool failure. The Kurtosis values decreased but RMS voltages increased as the cutting speed increased, in both continuous and interrupted cutting. RMS voltage is suddenly increased but Kurtosis value is suddenly decreased when tool failure condition. Power spectrum density of AE signals when tool failure reaches extreme value around 0.065 cycles/ .mu. m.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.351-352
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• 2015

Thyristor-controlled series capacitor (TCSC) is a power electronic-based device that provides a fast and controllable series compensation of transmission line reactance. To match with laboratory facilities and for further research initiatives, a practical laboratory scale TCSC was designed and fabricated in this paper. The TCSC parameters were designed based on the terminologies such as percentage of compensation, boost factor and resonance factor. According to the design parameters, a prototype laboratory scale TCSC with a constant reactance controller was fabricated and tested. The measured results from the laboratory scale TCSC demonstrate the ability of the TCSC to provide rapid control of series reactance of a transmission line.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.900-903
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• 2003

An identification method of induction motor parameters such as rotor time constant and mutual inductance at standstill condition is discussed assuming that stator resistance and leakage has already been obtained applying two different DC voltage and single phase voltage to the induction motor, respectively. This proposed scheme is implemented by means of Model Reference Adaptive Control (MRAC) technique, which uses a rotor flux equation in voltage model as a reference model and one in current model and is demonstrated through experiment.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.182-185
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• 2003

This paper combines the adaption of MRAS with the ability of NN for better modeling of nonlinear systen It presents an MRAS using an NN in the adaption mechanism. The technique is applied to a IPMSM drive. The torque constant and stator resistance variations on the speed and position estimations over a wide speed range has been studied. The NN estimators are able to track the varying parameter of different speeds with consistent performance. The validity of the proposed estimator is confirmed by the operating characteristics controlled by neural networks control.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.384-387
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• 1998

This paper presents a newly developed speed sensorless drive using RLS(Recursive Least Squares) based on Neural Network Training Algorithm. The proposed algorithm based on the RLS has just the time-varying learning rate, while the well-known back-propagation (or generalized delta rule) algorithm based on gradient descent has a constant learning rate. The number of iterations required by the new algorithm to converge is less than that of the back-propagation algorithm. The RLS based on NN is used to adjust the motor speed so that the neural model output follows the desired trajectory. This mechanism forces the estimated speed to follow precisely the actual motor speed. In this paper, a flux estimation strategy using filter concept is discussed. The theoretical analysis and experimental results to verify the effectiveness of the proposed analysis and the proposed control strategy are described.

• Journal of environmental and Sanitary engineering
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• v.13 no.3
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• pp.72-78
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• 1998

For investigation into gas permeation characteristics, the porous alumina membrane with asymmetrical structure, having upper layer with 10 nanometer under of pore diameter and lower layer with 36 nanometer of pore diameter, was prepared by anodic oxidation using DC power supply of constant current mode in an aqueous solution of sulfuric acid. The aluminium plate was pre-treated with thermal oxidation, chemical polishing and electrochemical polishing before anodic oxidation. Because the pore size depended upon the electrolyte, electrolyte concentration, temperature, current density, and so on, the the membranes were prepared by controling the current density, as a very low current density for upper layer of membrane and a high current density for lower layer of membrane. By control of current quantity, the thicknesses of upper layer of membranes were about $6{\;}{\mu}m$ and the total thicknesses of membranes were about $80-90{\;}{\mu}m$. We found that the mechanism of gas permeation depended on model of the Knudsen flow for the membrane prepared at each condition.