• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1427-1432
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• 2004

This paper proposes transformerless power conversion system consisting of a single-phase diode rectifier and a shunt hybrid filter for the electric-railway system. The hybrid filter consists of a single tuned LC filter per a phase and a low-rated NPC type multi-level inverter. Compared with conventional active filters. Transformers are not used. Also, LC filter works as not only a harmonic filter tuned at the 5th harmonic frequency but also a switching-ripple filter. The rating of the active filter can be decreased by using a NPC type multi-level inverter. The simulation results confirm the validity of the system

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.9
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• pp.572-577
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• 2000

This paper describes the test results of a single phase 3kVA high temperature superconducting power transformer. The tapes are made with Bi-2223 and have silver alloy as the matrix. Four double pancake windings are used. Among them two double pancake windings are connected in series for high voltage winding and the others are connected in parallel for low voltage winding. The rated voltage and current of primary winding and secondary winding are 220/110V. 13.7/27.3A. Fundamental characteristics are obtained through short circuit and no load test. The over load capability and characteristics are investigated.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.12
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• pp.1157-1162
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• 2009

The aerodynamic torque and power caused by the interaction between the wind and blade of wind turbine are highly nonlinear. For this reason, the overall dynamic behaviors of wind turbine have nonlinear characteristics. The aerodynamic nonlinearity also affects properties of torque control for wind turbine. In this paper, the nonlinear aerodynamic property according to the wind speed below rated power and its effects on the torque control system are investigated. Nonlinear parameter representing change of aerodynamic torque with respect to rotor speed is obtained by linearization technique. Effects of this aerodynamic nonlinear parameter on the closed-loop torque system with PI controller for an 1.5 MW wind turbine are presented.

• New & Renewable Energy
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• v.10 no.4
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• pp.3-8
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• 2014

Both of induction generator and synchronous generator is available in the hydroelectric power plant. If the output of the power station is large, the synchronous generator is mainly used but when its output is low, the induction generator is often used. If the output capacity is small, there is a case in which induction motor is used as a generator. Torque at rated operation and start of the induction motor is different depending on the shape of the rotor. Small and medium-sized squirrel-cage induction motor is used primarily double cage rotor or deep bar. In this study, we attempt to interpret characteristics for double cage rotor or deep bar that occur when operating in the induction generator based on the parameters that have been designed and manufactured as an induction motor.

• Journal of Power System Engineering
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• v.19 no.4
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• pp.89-96
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• 2015

This paper investigates some strategies to overcome the chattering problem of the conventional sliding mode observer (SMO) and to improve the rotor position estimation performance for full range sensorless control of a PMSM. An adaptive observer gain based on the Lyapunov's stability criterion and a cascade low pass filter with advanced phase delay compensation were proposed to reduce the chattering problem and to strengthen the filtering capability of the SMO. Several cases studies through experiments were carried out to confirm conventional SMO's problems and effectiveness of the proposed strategies. The experimental results show that the proposed method gives precise estimation on speed and rotor position when the motor rotates on 2% of its rated speed.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.493-495
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• 1995

Recently, as power transformer capacity is getting larger, vibration noise of transformer would be large and unexpected failuare of transformer give enormous economic loses, So we aquaire vibration signal, which is maked from transformer windings, core that are airtight out box with in insulation oil, and out box. Also we are fixed rated voltage and changing load current, analyize frequency domain of each vibration signals.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.1
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• pp.24-28
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• 2014

An induction motor is most widely used to obtain driving force in the industrial field. The induction motor is generated a high current at starting. A starting current is often more than five times of rated current. A high starting current can cause problems such as voltage drop in the power system. In order to solve these problems, a reactor starting method has been widely applied in a large motor capacity. There are differences in the operating characteristics of induction motor corresponding the switching time of reactor tap. In this study, I analyzed that current, torque, power of induction motor are different from changing time and tap setting values of reactor tap.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.367-372
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• 2012

In nuclear plants, UVR (under voltage relay, 27r) of 1E bus, which protected and supplied power to essential loads, to safety trip of reactor and supplied to starting signal of EDG (emergency diesel generators) automatically. therefore UVR tolerances setting and calculation method has been important to nuclear facility. If calculation and tolerances values differ or ignore, may induced power loss and economical loss by protective failure. This paper show results for calculation methods, and whether dependant or independent methods for factors. included whether PT (potential transformer/voltage transformer) tolerance or not adapted, and based on UVR setting method within a difference minimum and maximum of rated voltage to safety operation in nuclear plants.

• Wind and Structures
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• v.17 no.6
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• pp.671-680
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• 2013

Static aeroelastic is investigated in a wind turbine blade. Imposed to different loadings, the very long and flexible structures of blades experience some changes in its preliminary geometry. This results in variations of aerodynamic loadings. An iterative approach is developed to study the interactions between structure and aerodynamics evaluating variations in induced stresses in presence of aeroelasticity phenomenon for a specific wind turbine blade. A 3D finite element model of the blade is constructed. Aerodynamic loading is applied to the model and deflected shape is extracted. Then, aerodynamic loadings are updated in accordance with the new geometry of the deflected blade. This process is repeated till the convergence is met. Different operational conditions consisting of stand-by, start-up, power production and normal shut-down events are investigated. It is revealed that stress components vary significantly in the event of power production at the rated wind speed; while it is less pronounced for the events of normal shut-down and stand-by.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.1018-1023
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• 1998

This paper presents an effective control scheme incorporated in the voltage-fed half-bridge series resonant inverter for induction heating applications, which is based upon a load-adaptive tuned frequency tracking control strategy using PLL(Phase Locked Loop) and its peripheral control circuit. The proposed control strategy ensures a stable operation characteristics of overall inverter system and ZVS(Zero Voltage Switching0 operation in spite of sensitive load parameters variation as well as power regulation, specially in the non-magnetic heating loads. The simulation results and the performance characteristics in the steady-state are shown as compared with the experimental results for a prototype induction cooking system rated at 1.2kW.