• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.302-310
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• 2008

In order to evaluate the nominal rating of breakers in distribution system due to the increased capacity and operating conditions of power transformers in 154 kV substation, the fault currents in distribution system were calculated by the conventional method and simulations of PSCAD/EMTDC program. Consequently, under the condition of the parallel operation of transformers, the fault currents exceed the nominal current of the breakers in some areas. Without NGR at the secondary neutral of the transformer, the current of single line-to-ground fault was bigger than that of 3-phase fault. Therefore, the results clearly show that the measures to limit the fault currents in distribution system are needed when the increased capacity of power transformers is introduced into 154 kV substation.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1104-1105
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• 2015

Recently, electric power demand increase due to the rapid industrial development. As a result, a power system has been expanded and fault currents are raised. Fault current is detriment effect on protective equipment. Superconducting fault current limiter(SFCL) is one of the solution to solve the fault current reduction. This paper analyzed operating characteristics according to applied location of SFCL in a transmission power system through the PSCAD/EMTDC simulation.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.525-528
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• 2002

A Novel Zero Current Switching(ZCS) Pulse Width Modulation(PWM) boost converter for reducing two rectifiers reverse recovery related losses Is proposed. The switches of the proposed converter are operating to work alternatively turn-on and turn-off with soft switching(ZVS, ZCS) condition. The reverse recovery related switching losses and EMI problems of the proposed converter eliminates the reverse recovery current of the freewheeling diode(D, Dl) by adding the resonant inductor Lr, in series with the switch S2. The voltage and current stresses of the components are similar to those in its conventional hard switching counterpats. As mentioned above, the characteristics are verified through experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.382-387
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• 1998

The adaptive hysteresis band current control method using neural network is proposed to hold the switching frequency of PWM inverter constant at any operating points of ac motor. The adaptive hysteresis band equation is derived as the teaching signal of neural network. and then the structure and learning algorithm of the neural network a are suggested. The simulation results show that the switching frequency of PWM inverter is held constant at any operating conditions of ac motor and the proposed method has good transient performance of stator current.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.409-416
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• 2000

In case of operating two converters in parallel with ZCT operation method using one current sensor for fault tolerance by system characteristics, identifying fault detection and isolation is difficult of which converter is fault since the ZCT output is a difference of two converters' supply current when a converter has fault. This thesis suggest a fault detection and isolation method of converter in case of operating two converters in parallel for fault tolerant system and verified this suggested method through an experiment.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.376-377
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• 2010

In this paper, novel unidirectional auxiliary resonant commutated pole is proposed to improve the performance of zero-voltage soft-switching inverter. The proposed circuit keeps the advantages of the original soft-switching inverter, while providing more effective resetting capability in magnetizing current. Based on the advanced reset mechanism, auxiliary switches operate under a complete zero-current condition. The operating principle and steady-state analysis are presented theoretically, according to its operating modes. Accordingly, it proves the fact that the proposed unidirectional auxiliary resonant commutated pole breaks an unwanted magnetizing current loop effectively. The performance of the proposed circuit is verified by several simulation results.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.2
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• pp.74-78
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• 2003

This paper describes the operating characteristic analysis of the PM-type linear oscillatory actuator used as a magnetic circuit breaker for the electromagnetic field, electric circuit, and mechanical motion problems. Transient calculations are based upon a 2D finite element magnetic field solution including non-linearity of materials. Changes of the dynamic characteristics from the eddy current in the plunger are quantified from finite element analysis. A new laminated model is proposed to decrease the eddy current effect.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.791-792
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• 2006

In motor design, an important factor is the content of silicon in coss material, which can effect the saturation of magnetic circuit and coss loss. While the content of silicon is high, the core loss will be reduced. At the same time, in order to assure the effective flux, the magnetizing current must be increased and then the copper loss becomes higher. Therefore the material with high content of silicon, which is used in the motor, can not always give the high efficiency. In this paper flux linkage of two different material s10 and s60 is compared according to the operating region and then exciting current to obtain same flux is estimated. By comparing core loss and copper loss between two material with the estimated current and flux linkage, this paper presents a criterion in determining the material for higher efficiency

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.6
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• pp.951-957
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• 1994

We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.2
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• pp.53-57
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• 2017

This papers propose a Hall-effect sensors position error compensation method in a sunroof system using a BLDC motor with a low-cost MCU. If the BLDC motor is controlled with this wrong position, the torque ripple and operating current can be increased and the average torque also decreases. Generally, sunroof system has characteristics that operate at constant load for several seconds. It is possible to find the minimum operating current value while changing the position of the Hall-effect sensor during the sunroof operation by using these characteristics. Therefore, propose a method to change the Hall-effect sensor position and find the minimum current value. The validity of the proposed algorithm is verified through experiments.