• Electrical & Electronic Materials
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• v.9 no.1
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• pp.24-29
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• 1996

A composite piezoelectric ceramic transducer is fabricated with three piezoelectric ceramic disk vibrators and two sheets of thin insulator. Its equivalent circuit is derived from the Mason's model of a thickness-driven piezoelectric vibrator. When the electric input near its fundamental resonance frequency is applied to the center vibrator and the output voltages across the left and the right vibrators are connected in series to the resistor loads, the load characteristics at resonance frequencies under the various resistor loads and the frequency characteristics near the resonance frequency without load are investigated. Furthermore, symbolic expressions for input impedances, voltage ratios, resonance frequencies, and bandwidths are derived. The data calculated from those symbolic expressions are agreed well with the measurement data.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.345-350
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• 2019

This study deals with the design of a modular converter that can convert the output voltage according to the size of the load. The efficiency of the converter depends on the size of the load and is generally less efficient for lower loads. Therefore, it is more efficient to construct a small capacity modular converter than to manufacture a large capacity converter and it determines the capacity of the system through the parallel connection of the converter module according to the load size. In this paper, we will introduce a modular DC / DC converter designed to control the number of modules according to the load. A programmable resistor is placed at the output of the module for parallel connection of the module, and the voltage is regulated by adjusting the variable resistor. A system controlled in this way was found to exhibit an efficiency improvement of about 32%.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.12a
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• pp.78-82
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• 2001

Electronic Weighting Machine is used an electronic scale which has many trouble because of broken load cells. In this paper, we propose an intelligent Diagnosis System will for an electronic weighting machine using fuzzy logic. It's purpose be detect of the load cell's trouble. The electronic circuit of system, which call 'junction box', will be connected resistances in a series at circuit of Wheatstone Bridge for monitoring the condition of load cells.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.435-442
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• 2000

In this paper, we analyzed RF-DC conversion efficiency for the dual -polarization rectenna and the antenna position changing. Dual-Polarization rectenna consist of a two major parts, receiving antenna and rectifying circuits. We made dual-polarization 2.45GHz rectenna using the two dipole antennas and patch antenna. Rectifying circuit is consisted by a Schottky-Barrier diode with a large forward current and reverse breakdown voltage. The results of RF-DC conversion efficiency for the each of designed dual-polarization rectenna has 69.1% with 360$\Omega$(dipole type) and 75.4% with 340$\Omega$(patch type ) optimum load resistor. When the each of dual-polarization rectenna has optimal load resistor, it's conversion efficiency shows of $\pm$20% in dipole type and $\pm$5 in patch type at 0~180。position.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.10
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• pp.99-105
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• 2010

This paper discussed the theoretical simulation results for developing the blumlein pulsed power source and showed the circuit configuration and the discharge characteristics of the realistic manufactured pulsed power system. In the simulation, the output voltage characteristics at a load resistor showed the general impulse shape when the impedance of a single coaxial cable is matched with the that of a load resistor. In addition, it is confirmed that output values of the pulsed power can be easily controlled by the duplication of coaxial cables and the pulsed waveform showed the general impulse characteristics. Specifically, the inception discharge voltage in the gap distance of 5[mm] between needle and plane electrodes is about 20[kV] and which is lower than about 29[kV] in 9[mm] due to the difference of the reaching time of the inception voltage. Therefore, this paper showed that the output voltage of the blumlein pulsed power source can be easily controlled.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.1
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• pp.30-36
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• 1993

A simple discontinuous conduction mode(DCM) flyback type active power factor corrector for low power supply resents an effective resistive load to its power input. It is therefore well suited as an inexpensive high power factor rectifier for office equipment. An equivalent circuit model for the Active Power Factor Corrector based on the "Loss Free Resistor" concept is presented. This simple model correctly describes the basic power processing properties of the Active Power Factor Corrector, including input port resistor emulation, output port power some characteristics.teristics.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.280-281
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• 2011

Special Protection Scheme(SPS) that operates scenarios about faults beyond the normally protective action is wide system protection technology for the purpose of wide areas protection. Therefore, the SPS focuses on the improvement of the power supply capability by protecting the system rather than protecting the system equipments. Since the SPS requires emergency operation, the operation schedule is set up in advance by analyzing various scenarios. Since the SPS's action scheme uses generator tripping and is a classical method it is presently the most powerful one. However, as the setting of SPS is set to the most severe disturbance, the scheme tends to trip more generators than required to prevent fault propagation. It is highly likely that tripping generator units to prevent fault propagation would result in difficulty of system management and possibility of load shedding. Accordingly, it is desirable that generators are connected to the system within the range that ensures system stability and intelligent SPS is currently under development to solve the problem being stated. In this paper, as a part of developing the intelligent SPS, application of the fast-valving and braking resistor scheme to the generators is being proposed and analysed to reduce the number of tripped generators.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1062-1064
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• 2005

3 phase 4-wire system has been widely used in the customer's application due to merit of 1 bank construction of loads such as 1-phase lighting, heat and 3-phase motor. But if the load distribution is not uniformed by the operation conditions, voltage unbalance is highly appeared by the difference of each phase current value. Especially, if the linear load such as resistance or inductive load has different power factor value, voltage unbalance factor is not the same due to the phase angle and magnitude of each phase voltage. In this paper, we composed the measurement device and analyzed by varying of load pattern.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.166-169
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• 1990

The purpose of the circuit breaker on power system is to disconnect the faulty part from the system and to maintain the integrity of the system. With switching overvoltages are generated. When the system voltages become higher, switching overvoltage is important factor in insulation co-ordination. Since the no-load reclosing overvoltage with inductive source is severe, this paper deals with the reclosing overvoltage and the effect of closing resistor. This reclosing overvoltage of 27-bus model system with and without closing resistor is analyzed by using EMTP (Electro-Magnetic Transients Program) for both deterministic and Stochastic model.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1672-1681
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• 2016

This paper proposes a wireless parallel operation method of three-phase modular UPS inverter using resistive droop control. Furthermore, it applies a virtual resistor to droop control so that the output impedance of UPS inverter gets closer to resistive. It makes resistive droop control effective. The simulation using PSIM was performed in order to verify the validity of proposed algorithm. After consisting two-parallel system with three-phase modular UPS inverter, the experiment according to resistive load was conducted. It demonstrated the performance of current sharing and power sharing.