• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.429-429
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• 2009

Nanoporous anodic alumina membranes (NAAM) with high-density through-hole pores fabricated by hard anodization of aluminum in 0.3 M oxalic acid under the applied voltage of 40 (mild anodization), 80, 100, 120 and 140 V were investigated. The current-time responses monitored using a PC-controlled anodization cell and the corresponding pore structures attainable from field-enhanced scanning electron microscopy (FE-SEM) were analyzed in order to establish the optimum fabrication process. The nanoporous structure can be produced for all the voltage conditions, while the stabilized through-hole pore formation seems to occur at 40, 80 and 140 V. The growth rate under 140 V hard anodization was over 30 times higher than under 40 V mild anodization (1.5 um/hr).

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.181-183
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• 2003

In this paper, phase controlled series resonant converter(PCSRC) system for control power supply in base station is suggested. PCSRC system is robust to load variations because it is POSR(parallel output series resonant) type. And it provides stable output voltage by changing phase angle of MOSFET switches to input voltage variations. Firstly, operation analysis about suggested series resonant converter system was carried. Then Computer simulations using PSIM were carried to prove characteristics of suggested system.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.45-48
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• 2003

Recently the PDP is the most remarkable media for a next generation display device. In this paper, we proposed the PDP dedicated DC-DC converter using a new soft switching method because the PDP has a lot of power dissipation so we need to develope. The proposed converter using one transformer has soft switching and a advantage to lower voltage stress in switch and also is predicted to have high power efficiency. we proposed the principles and theory using the zero voltage switching and verified the validity through a simulation.

• Journal of Power Electronics
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• v.8 no.3
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• pp.275-279
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• 2008

An LLC series resonant converter has many unique characteristics and improvements over PWM topologies. However, many output capacitors are needed in parallel to satisfy output voltage ripple and the rated ripple current of the capacitors. This paper deals with a novel two phase interleaved LLC resonant converter using a phase of the resonant capacitor. The proposed converter can satisfy output voltage ripple and a rated ripple current of capacitors with few output capacitors, relatively. The operation and features are considered in detail and a prototype with a 12V-100A output is investigated.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.704-705
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• 2011

At present, the widely used wind power generators in the whole world are fixed speed induction generator (FSIG) and doubly fed induction generator (DFIG). The models of FSIG and DFIG wind power generation system connected with the grid are built, and their steady-state and transient characteristics are studied. A new coordinated control strategy using both the grid and rotor side converters of DFIG for voltage regultation and reactive power support is put forword to improve the steady-state and transient performance of the FSIG in the case of DFIG in parallel with FSIG.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.706-707
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• 2011

The insertion of the crowbar system in the doubly fed induction generator rotor circuit for a short period of time during grid disturbance enables a more efficient way of limiting transient rotor current and hence protecting the rotor side converter (RSC) and the DC - link capacitor. When crowbar is activated at fault occurrence and clearance time, RSC is blocked while DC -link capacitor and the grid side converter (GSC) can be controlled to provide reactive power support at the PCC and improve the voltage which helps to comply with grid codes. In this paper, control strategies for crowbar system to limit the rotor current during fault is presented with RSC and GSC controllers are modified to control PCC voltage during disturbance to enhance DFIG wind farm to comply with some strict grid codes. Model simulated on MATLAB/Simulink verify the study through simulation results presented.

• Proceedings of the KIPE Conference
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• 2007.11a
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• pp.47-49
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• 2007

For the magnetron, two kinds of auxiliary power is required to generate proper heat and electromagnetic field. In this paper the development of filament power supply and magnet power supply for high power industrial magnetron is studied. The filament power supply which is generate proper heat, even it doesn't require high power like main power supplies, has many consideration such as high voltage insulation and power control coordinated with high voltage cathod current to maintain constant heat generation. The novel control method using constant resistance control is proposed for accurate control of filament power supply.

• KSTLE International Journal
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• v.2 no.1
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• pp.22-28
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• 2001

A resin bonded copper-graphite brush was investigated to evaluate the characteristics electrical signal transmission through a sliding contact as a function of the relative amount of graphite and copper in the brush. Particular attention was given to the correlation between electrical signal fluctuation and tribological properties in an electrical sliding contact system. A ring-on-block type tribotester was used for this experiment and the ring was made from pure copper. Results showed that a copper-graphite brush at a particular composition range exhibited the most stable frictional behavior with a minimum voltage drop. The amount of voltage drop at the friction interface was affected by the surface roughness, transfer film formation at the friction interface, and the real area of contact. Microscopic observations and the surface analysis showed a good agreement with the results from this experiment. The results also indicated that the electrical signal flunctuation was directly associated with the oscillation of the coefficient of friction during sliding by nanoscale variation of contacts at the friction interface.

• Journal of Electrical Engineering and Technology
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• v.3 no.3
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• pp.401-407
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• 2008

The dynamic model and displacement control of piezoelectric actuators, which are commercially available materials for managing extremely small displacements in the range of sub-nanometers, are presented. Piezoceramics have electromechanical characteristics that transduce energy between the electrical and mechanical domains. However, they have hysteresis between the input voltage and output displacement, and this behavior is very demanding and complicated. In this paper, we propose a method of designing the control algorithm, and present the dynamic modeling equations that represent the hysteretic behavior between input voltage and output displacement. For this process, the piezoelectric actuator is treated as a second-order linear dynamic system and system constants are determined by the system identification method. Also, a classical PID controller is designed and used to regulate the output displacement of the actuator. To evaluate the performance of the proposed method, numerical simulation results are presented.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.713-717
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• 2004

This is a thesis that a quarter-brick size of 100W class open-frame type on board power module comprising telecommunication application is reported. The input voltage is established between 36 and 75 in range in order for power module to be utilized for the telecommunication application, and output were set at 3.3V and 30A. A number of parts used for transformer, inductor, and hit sink are composed of PCB in order for DC-DC converter to be lowered below 8 mm. A constant current control circuit was annexed to the system as well as basic protection prototypes such as over-voltage, over-current, and over-temperature were well considered to enhance more credibility, and were tested. As a result, high circuit performance and credibility turned out to be significant.