• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.12
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• pp.691-699
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• 2004

SRM(Switched Reluctance Motor) drives require the accurate position information of the rotor. These informations are generally provided by a tacho generator or digital shaft-position encoder These speed sensors lower the system reliability and require special attention to noise. This paper describes a new approach to estimating SRM speed from measured terminal voltages and currents for speed sensorless control. The described method is based on the sliding mode observer. The rotor speed and position observers are estimated by the adaptation law using the real and estimated currents. However, the conventional adaptive sliding mode observer based on the variable structure control theory has some disadvantages that the estimated values including the high-frequency chattering and the steady state error generated due to the infinite feedback gain chosen and the discontinuous control input. To reduce the chattering and steady state error, an integrator is also inserted in the sliding mode observer strategy. The described adaptive sliding mode observer decreases the vibration to the switching hyper-plane of the sliding mode by adding integrator. The described methodology incorporates the Lyapunov algorithm to drive the rotor speed and the stator resistance such that it can overcome the problem of sensitivity in the face of SRM parameter variation. Also, without any mechanical information. The rotor speed of SRM is obtained form adaptive scheme. The described method is verified through the simulation and experiment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1123-1126
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• 2003

In this paper, the emission properties of electrodeless fluorescent lamp were discussed using the inductively coupled plasma. To transmit the electromagnetic energy into the chamber, a RF power of 13.56MHz was applied to the antenna and considering the Ar gas pressure and the RF electric power change, the emission spectrum, Ar- I line, luminance were investigated. At this time the input parameter for ICP RF plama, Ar gas pressure and RF power were applied in the range of $10{\sim}60m$ Torr, $10{\sim}300W$ respectively.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.5-14
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• 1999

Free vibration characteristics of a cantilevered laminated composite beam with multiple non-propagating transverse open cracks are investigated. In the present analysis a special ply-angle distribution referred to as asymmetric stiffness configuration inducing the elastic coupling between chord-wise bending and extension is considered. The multiple open cracks are modelled as equivalent rotational springs whose spring constants are calculated based on the fracture mechanics of composite material structures. Governing equations of a composite beam with open cracks are derived via Hamilton's Principle and Timoshenko beam theory encompassing transverse shear and rotary inertia effect is adopted. The effects of various parameters such as the ply angle, fiber volume fraction, crack numbers, crack positions and crack depthes on the free vibration characteristics of the beam with multiple cracks are highlighted. The numerical results show that the existence of the multiple cracks in an anisotropic composite beam affects the free vibration characteristics in a more complex fashion compared with the beam with a single crack.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.279-282
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• 2002

Recently, gas turbines for power generation adopt multistage DLN(Dry Low NOx) type combustion, where diffusion combustion is applied at low load and, with increase in load, the combustion mode is changed to lean premixed combustion to reduce NOx emissive concentration. However, during the mode changeover from diffusion to premixed flame, unfavorable phenomena, such as flashback, high amplitude combustion oscillations, or thermal damage of combustor parts could frequently occur. In the present study, to apply for the analysis of such unfavorable phenomena, three-dimensional CFD investigations are carried out to compare the detailed flow characteristics and temperature distribution inside the gas turbine combustor before and after combustion mode changeover. The fuel considered here is pure methane gas. A standard $k-{\varepsilon}$ turbulence model with wall function and a P-N type radiation heat transfer model, have been utilized. To analyze the complex geometric effects of combustor parts on combustion characteristics, fuel nozzles, a swirl vane f3r fuel-air mixing, and cooling air holes on the combustor liner wall, are included in this simulation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.2
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• pp.124-131
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• 1989

This paper showed that the system reliability optimization problem with sereval failure modes at each subsystem can be treated as efficient computational algorithm proposed here. This algorithm was developed by considering a generalized upper bounding which always exists in constraints when the system reliability optimization problem may be reformulated as 0-1 integer programming problem. We demonstrated the optimal allocation of redundant units for system reliability by using the proposed algorithm. Our algorithm is superior to others in terms of number of iterations and variables used.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.107-115
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• 1997

In this paper, a 23 GHz push-push oscillator was designed and fabricated for 23 GHz point-to-point communication using split ring resonator. The split ring resonator was equivalent circuit and numerical method of MPIE(Mixed Potential Integral Equation). The analysis of split ring resonator which coupled between microstrip lines was carried out with transmission-mode using this results. The fabricated oscillator showed the output power of 4 dBm, the 1'st harmonic suppression of -20 dBc, the 3rd harmonic suppression of -34 dBc, a SSB phase noise of -109 dBc / Hz at 1MHz offset frequency from the carrier was achieved and 1.4 percents efficiency at 23 GHz. The experimental outputs were in good results with the theoretical and simulated results.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.1
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• pp.47-54
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• 2004

A new high voltage DC power supply is proposed. The proposed power supply is constructed with several power converters connected in series. It is easy to obtain high DC voltage for the same structure of each power converter. The output DC power of the proposed power supply can be disconnected from the load within several hundred microseconds at the instant of a load short-circuit fault. The rising time of the output DC voltage is also as small as several hundred microseconds, and there is no overshoot of the voltage because all of the output filter capacitors keep undischarged state even in load short-circuit condition. Therefore, the proposed scheme is suitable for the protection of frequent output short-circuit and fast on/off switching of output DC voltage. The proposed power supply has improved features such as simple structure, high power factor, and reduced size and volume compared with the conventional schemes. The operating principle is described and the validity of the proposed scheme is proved through simulations and experiments.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.12
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• pp.771-777
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• 2000

This paper deals with the design and fabrication of a novel superconducting power supply system, and characteristics have been investigated through experiments. Superconducting power supply consists of rotating and static parts, and superconducting magnet. In this experiment, superconducting foils were placed in parallel within the static part of the machine, pumping currents were measured with respect to rotor speeds and excitation currents. In addition, in order to observe the rotating flux distribution in the superconducting foils, several hall-sensors were placed in it. With the flux distribution acquired, effect of the flux on the superconducting foil during the process of current pumping has been discussed. Also, the general operational characteristics of the superconducting power supply system have been investigated on the basis of the current and voltage data, and magnetic field values acquired through the experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.4
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• pp.76-82
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• 2006

Flutter analyses are performed for the KF-16D aircraft with brand new ALQ-X ECM pod. A flutter analysis method using test modal data is proposed and validated using published F-16 modal data and flutter analysis results. Ground vibration test is performed for KF-16D stands on its landing gears. Attained modal data are transformed to free-free condition of KF-16D aircraft with ALQ-X pod and ALQ-119 pod, respectively. As the results of comparison of flutter analyses, ALQ-X is cleared to be operated in the flight envelope authorized for existing ECM pods.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.171-178
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• 2000

We present a numerical model which enables to analyze $1.47mu$m amplification band characteristics for thulium doped fluoride fiber amplifiers. We focused on upconversion pumping scheme, thus many transitions affecting $1.47mu$m band amplification was considered simultaneously. Backward propagating waves and transverse mode were also considered in the model. The parameters for modeling were then acquired using published experimental data and related theories such as Judd-Ofelt theory for radiative transition, empirical energy gap law for non-radiative transition, and McCumber relations for cross-sections. The simulation showed well-matched results with experiment and internal dynamics. amics.