• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.22-25
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• 2001

In this paper, a fuzzy advance angle control method is described to drive an industrial low voltage SRM (Switched Reluctance Motor) for 10kW forklift truck. SRM has a highly non-linear characteristic that is due to change the rotor and stator. And low voltage SRM is designed that its phase resistance and phase inductance is very low to inject high current into the phase windings. In this reason, the proper current control is necessary to drive the low voltage SRM efficiently. SRM has positive torque at increasing inductance region and negative torque at decreasing inductance region. Due to this reason, the current has to be built up in the increasing phase inductance part as soon as possible. Therefore, the phase switch must be turned on before the phase inductance increases, and this angle is called as the advance angle. Also, the phase current has to be dropped before the phase inductance decreases. Fuzzy logic is a flexible and general-purposed method of implementing non-linear functions and as such it is useful in control applications. Consequently, we designed a fuzzy advance angle controller to control the phase current appropriately.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.3
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• pp.365-370
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• 2013

Generally, photovoltaic modules consist of glass, EVA, Solar Cell, back sheet and ribbon. But EVA, solar cell, ribbon affect electric output with temperature. EVA is a change in the transmittance of light from the sun. In addition, the solar cell output is decreased with temperature and the ribbon increases resistance. Transmittance and reflectance of glass and EVA were measured. In this paper, the characteristics of the components of PV module as EVA and Glass, ribbon were studied by variable temperature. effects on material properties investigated. As a result, glass is independent in temperature variation. EVA was the reduction 1~4% in transmittance. Solar cell decrease 0.469[%/$^{\circ}C$] in electric output by temperature variation. Other factors was controlled in solar cell..

• Journal of Electrical Engineering and Technology
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• v.13 no.5
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• pp.1927-1934
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• 2018

In this paper, we studied the state of charge (SOC) estimation algorithm of a high-capacity lithium secondary battery for electric vehicles (EVs) considering temperature characteristics. Nonlinear characteristics of high-capacity lithium secondary batteries are represented by differential equations in the mathematical form and expressed by the state space equation through battery modeling to extract the characteristic parameters of the lithium secondary battery. Charging and discharging equipment were used to perform characteristic tests for the extraction of parameters of lithium secondary batteries at various temperatures. An extended Kalman filter (EKF) algorithm, a state observer, was used to estimate the state of the battery. The battery capacity and internal resistance of the high-capacity lithium secondary battery were investigated through battery modeling. The proposed modeling was applied to the battery pack for EVs to estimate the state of the battery. We confirmed the feasibility of the proposed study by comparing the estimated SOC values and the SOC values from the experiment. The proposed method using the EKF is expected to be highly applicable in estimating the state of the high-capacity rechargeable lithium battery pack for electric vehicles.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.5
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• pp.218-227
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• 2021

A thick film NTC thermistor for low temperature co-firing was manufactured by printing and sintering a paste prepared using NTC powder of Mn_1.5Ni_0.4Co_0.9Cu_0.4O₄ composition, lead free frit, and RuO₂ on a 96 % alumina substrate. The effect of frit and RuO₂ on the electrical properties of thick film NTC thermistor was studied. The resistance of the thick film NTC thermistor was higher than that of the bulk phase sintered at the same temperature, but it was found that the negative resistance temperature characteristic appeared more clearly and linearly in the resistance - temperature characteristic. On the other hand, the area resistance decreased as the sintering temperature increased, and the area resistance increased as the amount of frit added increased. The B constant of the thick film NTC thermistor was 3000 K or higher. Among them, it was found that the B constant of the thick film NTC thermistor made of paste with 5 wt% of frit added and sintered at 900℃ showed the highest B constant. Also, it can be seen that the area resistance decreased with the addition of RuO₂, and the change in the area resistance decrease of the thick film NTC thermistor obtained by sintering the paste containing 5 wt% of RuO₂ at 900℃ is the most obvious.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.211-211
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• 2009

YBCO coated conductor can change the stabilization layer for purpose and it leads advantages in Improvement of tape's critical properties and Application. Such properties rise possibility of using YBCO coated conductor for Superconductor Fault Current Limiter, therefore, we investigate changing properties under over current condition and limiting characteristics. In this study, YBCO coated conductor's current limiting characteristic stainless steel stabilization layer under condition of changing conductor's insulating layer. Consequently, the resistance followed insulating layer so we know that limiting characteristics.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.334-337
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• 2015

Pure ZnO, ZnO nanowires doped with 3 wt.% Ga (3GZO) and doped with 3 wt.% Ag (3SZO) were grown by a hot-walled pulse laser deposition (HW-PLD) technique. The optical and chemical properties of Ga and Ag doped nanowires was analyzed. Nanowires were determined to be under 200 nm in diameter and several μm in length. Change of significant resistance was observed and the gas detection sensitivities of ZnO, 3GZO and 3SZO nanawires were compared. The sensitivities of ZnO, 3GZO, and 3SZO nanowire sensors were measured at 300℃ for 1 ppm of ethanol gas at 97%, 48%, and 203%, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.21-23
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• 2002

In this paper, the electrochemical behavior of Viologen self assembly monolayer has been investigated with QCM, which has been known as nano-gram order mass detector. The self assemvly process of Viologen was monitored using resonant frequency $({\Delta}F)$ and resonant resistance(R). QCM measurements indicated a mass adsorption for Viologen assembling on the gold sufrace with a frequency change about 135[Hz] and calculated its surface coverage($\Gamma$) to be $3.5273{\times}10^{-9}[mol/cm^{2}]$. Also reversible redox process was observed and analyzed with ionic interaction at the Viologen/solution interface using ${\Delta}F$.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.8
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• pp.316-324
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• 1984

In the wound rotor induction motor, the external resistor is usually added to the rotor circuit in order to limit the starting current. In this scheme, whilst the starting current is limited, the available torque is remarkably reduced. In this paper, to improve the starting characteristics the stator current can be maintained constant by adjusting the external resistor. To change the external resistor, teh chopper and the resistor is connected in parallel, and the chopper duty cycle is adjusted by microprocessor. The duty cycle is calculated according to the actual speed of motor by microprocessor look-up table map. In this suggested scheme, the starting characteristics are remarkably improved without over-current. The starting time of this system is reduced by 20-48 Percent compared with fixed extemal resistance system in the same load.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.49 no.1
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• pp.19-25
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• 2000

This paper describes the sheath induced voltage in underground transmission cable system which will be operated with cable cover protection unit(CCPU). Simulation was carried out to analyze the sheath induced voltage in the real cable system which was installed by 154㎸ CV cable in the case with and without CCPU. The sheath induced voltage will be also analyzed according to the change of grounding method, fault resistance and fault angle. Simulation was performed using EMTP and ATP Draw, the simulation results show whether the CCPU in necessary or not in underground transmission power cable system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.9
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• pp.870-875
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• 2005

We measured the optogalvanic signal and discharge voltage-current(V-I) curve under the two different discharge conditions with different buffer gases, Ar, and Ne. When the Gd was used as a cathode material at low discharge current less than 10mA, a significant change was observed in the current-voltage curve. Time resolved optogalvanic signal measurement were measured by the diode laser of which wavelengths correspond to metastable transition line of these gases (Ar, Ne). From these measurements, we found that the characteristics of the V-I curve strongly depend on the Penning ionization process.