• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.11
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• pp.9-16
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• 2010

This paper examines the temperature characteristics of an Optical CT (optical current transformer) using the Faraday effect for measuring high current in a super high voltage-power apparatus. It is performed as follows by the sensor for embodying Faraday effect. $\cdot$ A single-mode optical fiber capable of maintaining a polarization state is used. $\cdot$ A light source is applied at 1310[nm] to a Laser Diode. $\cdot$ The Linear of Faraday effect to a large current is evaluated and $\cdot$ A possible application using an Optical CT was shown. An Influence of Faraday effect to the surrounding temperature measured -40~50[$^{\circ}C$], and the characteristic of the current sensitivity was reported. An application using the results of the temperature compensation system was used in order to compensate for surrounding temperatures. A possibility of applying Optical CT for electric power apparatus was advanced further. We were able to confirm that this temperature calibration method can minimize the fluctuation of the output signal depending on the temperature conditions.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.1
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• pp.1-12
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• 2005

This paper deals with the HVDC stability according to controller types and control modes. From the viewpoint of controllers, the HVDC system which has PI, PD and PID, is designed considering the system response and stability. Also the HVDC system consists of multi-control modes like voltage control, current control and alpha control. Therefore, the HVDC stability analysis have to consider the above control modes and controller types. In this paper, the reduced model of HVDC control is analyzed in PSS/E(Power System Simulation/Engineering) and PSCAD/EMTDC.

• Transactions on Electrical and Electronic Materials
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• v.2 no.4
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• pp.1-6
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• 2001

In this paper, a 1.5 V high-gain high-frequency CMOS complementary operational amplifier is presented. The input stage of op-amp is designed for supporting the constant transconductance on the Input stage by consisting of the parallel-connected rail-to-rail complementary differential pairs. And consisting of the class-AB rail-to-rail output stage using the concept of elementary shunt stage and the grounded-gate cascode compensation technique for improving the low PSRR which was a disadvantage in the general CMOS complementary input stage, the load dependence of open loop gain and the stability of op- amp on the output load are improved, and the high-gain high-frequency operation can be achieved. The designed op-amp operates perfectly on the complementary mode with the 180° phase conversion for a 1.5 V supply voltage, and shows the DC open loop gain of 84 dB, the phase margin of 65°, and the unity gain frequency of 20 MHz. In addition, the amplifier shows the 0.1 % settling time of .179 ㎲ for the positive step and 0.154 ㎲ for the negative step on the 100 mV small-signal step, respectively, and shows the total power dissipation of 8.93 mW.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.1
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• pp.38-44
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• 2005

In a voltage source inverter, the dead time is necessary to prevent short circuits in the dc link. The dead time effect appears as a distortion of output voltages and currents. In recent years, the dead time compensation methods have been investigated in many literatures. This paper presents not the dead time compensation by sensing and calculation but the dead time elimination. The proposed inverter system doesn't need to sense load current and to calculate dead time. Adding some transformers to each leg, dead times in the inverter system are eliminated automatically. The proposed method is analyzed on each mode and verified through simulation results.

• Journal of Power Electronics
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• v.15 no.1
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• pp.256-267
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• 2015

Grid-connected transformerless photovoltaic (PV) inverters (TPVIs) are increasingly dominating the market due to their higher efficiency, lower cost, lighter weight, and reduced size when compared to their transformer based counterparts. However, due to the lack of galvanic isolation in the low voltage grid interconnections of these inverters, the PV systems become vulnerable to leakage currents flowing through the grounded star point of the distribution transformer, the earth, and the distributed parasitic capacitance of the PV modules. These leakage currents are prohibitive, since they constitute an issue for safety, reliability, protection coordination, electromagnetic compatibility, and module lifetime. This paper investigates a wide range of multi-kW range power rating TPVI topologies and classifies them in terms of their leakage current attributes. This systematic classification places most topologies under a small number of classes with basic leakage current attributes. Thus, understanding and evaluating these topologies becomes an easy task. In addition, based on these observations, new topologies with reduced leakage current characteristics are proposed in this paper. Furthermore, the important efficiency and cost determining characteristics of converters are studied to allow design engineers to include cost and efficiency as deciding factors in selecting a converter topology for PV applications.

• Journal of Power Electronics
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• v.14 no.3
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• pp.413-420
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• 2014

The conventional Phase-Shift Full-Bridge (PSFB) converter has a serious voltage spike because of the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches. To overcome this problem, an asynchronous active clamp technique employing an auxiliary DC/DC converter has been proposed. However, an exact analyses for designing the auxiliary DC/DC converter has not been presented. Therefore, the amount of power that is supposed to be handled in the auxiliary DC/DC converter is calculated through a precise mode analyses in this paper. In addition, this paper proposes a lossy snubber circuit with hysteresis characteristics to reduce the burden that the auxiliary DC/DC converter should take during the starting interval. This technique results in optimizing the size of the magnetic component of the auxiliary DC/DC converter. The operational principles and the theoretical analyses are validated through experiments with a 48V-to-30V/15A prototype.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3215-3217
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• 1999

In this paper, a new structure of realizing switching control logic for Data Weighted Average Technique is suggested. It uses memory and adder for summing past binary input and this summed data is used to select one switch in control logic. This control logic acts in parallel regardless of resolution so increasing resolution don't affect on converting speed. In this reason, high speed and high resolution D/A converter based on Data Weighted Average Technique could be made. In this paper, 4 bits current mode thermometer code D/A converter is degined and simulated by using HSPICE. Simulated results show that new structure of D/A converter has more than 250MHz converting speed and less than 0.0003[LSB] INL error. It is very useful in low power circuit because of using 3.3 V supply voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.9
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• pp.733-738
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• 2011

A novel design of a simple square-frame USM (ultrasonic motor) was proposed. The stator of the motor consists of a square-frame shape elastic body and four rectangular plate ceramics. The four ceramics were attached to inner surfaces of the square frame elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90 degree phase difference voltage were applied to the ceramics on vertical surfaces. To find a model that generates elliptical motion at outside of the stator, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As result, the model EL10EH3ET0.5CL4 which generates the maximum elliptical displacement was chosen by analyzing the resonance mode according to changes in frequency.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.285-288
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• 1996

The electronic operation of the gas discharge tube is controlled by the electrical energy as sinusoidal waveform in arbitrary frequency range, or as a sequence of pulses at a wide range of duty cycle, the gas composition, the kind of electrode and the vessel geometry. In this paper, the pulsed mode operated gas discharge tube is composed with mixed gas of IIg-Ne ( 10 Torr ), in the tube of 15.0 mm outer diameter and has variable color from red to blue with changing frequency and pulse width in high voltage. As increasing pulse width and frequency in the gas discharge tube, the phenomenons that the electron temperature in the positive column increases and the radiation from atoms of higher upper state energy levels increases, exist. The color have the locus from red (0.4972, 0.3128) to blue (0.2736, 0.2619) in CIE chromacity diagram with increasing pulse width and frequency. The changing method of pulse width and frequency has been shown to be suitable for the luminous color control.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.26-28
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• 2009

This paper proposes maximum torque control of IPMSM drive using adaptive teaming mechanism-fuzzy neural network (ALM-FNN) controller, model reference adaptive fuzzy tonal(MFC) and artificial neural network(ANN). This control method is applicable over the entire speed range which considered the limits of the inverter's current and voltage rated value. For each control mode, a condition that determines the optimal d-axis current $i_d$ for maximum torque operation is derived. This paper considers the design and implementation of novel technique of high performance speed control for IPMSM using ALM-FNN, MFC and ANN controller. The proposed control algorithm is applied to IPMSM drive system controlled ALM-FNN, MFC and ANN controller, the operating characteristics controlled by maximum torque control are examined in detail. Also, this paper proposes the analysis results to verify the effectiveness of the ALM-FNN, MFC and ANN controller.