• The Journal of the Korea Contents Association
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• v.18 no.10
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• pp.425-430
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• 2018

The battery system of an electric vehicle suffers from the problem the battery output and the service life decrease at low temperature. A Positive Temperature Coefficient(PTC) heater is used for maintaining room temperature but is heavy due to a complicated insulation structure. The larger the weight is, the lower the fuel economy of the electric vehicle is. On the other hand a induction heater have a simple insulation structure, which is effective in weight reduction and has a rapid temperature rise. The induction heater consists of an LC resonance circuit. The larger the capacitance is, the higher the price and weight is. Therefore, the inductance should be increased to reduce the capacitance. Also, the main heat source of the induction heater is coreloss. So, it is important to optimize inductance and coreloss in terms of electromagnetic field design. In this paper, the inductance and the coreloss according to the change of the induction heater structure were optimized through the Taguchi method and Finite Element Method(FEM) simulation.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.67-78
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• 2012

An electric double-layer capacitor(EDLC) is an electrochemical capacitor with relatively high energy density, typically hundreds of times greater than conventional electrolytic capacitors. EDLCs are widely used for energy storage rather than as general-purpose circuit components. They have a variety of commercial applications, notably in energy smoothing and momentary-load devices, and energy-storage and kinetic energy recovery system devices used in vehicles, etc. This paper presents an accelerated degradation test of an EDLC with rated voltage 2.7V, capacitance 100F, and usage temperature $-40^{\circ}C{\sim}65^{\circ}C$. The EDLCs are tested at $50^{\circ}C$, $60^{\circ}C$, and $70^{\circ}C$, respectively for 1,750hours, and their capacitances are measured at predetermined times by constant current discharge method. The failure times are predicted from their capacitance deterioration patterns, where the failure is defined as 30% capacitance decrease from the initial one. It is assumed that the lifetime distribution of EDLC follows Weibull and Arrhenius life-stress relationship holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.1
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• pp.23-28
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• 2002

In order to survey the radiation characteristics of pure line noise of unwanted noise from overhead high voltage AC transmission lines, a disk type gap noise generator was manufactured. Disk size which decides capacitance between the noise generator and earth was selected through preliminary indoor experiments and analysis by using surface charge method. The capacitance is one of principal parameters related to the injection of a proper noise current into lines. On the basis of the capacitance obtained from calculation, 5mm of space was given to the gap of the noise generator to be installed o test line and an aluminum disk of 60cm radius was made. The field experiments were performed with the noise generator hung on the Kochang 765 kV full scale test line. As the results, the useful data which can be used to analysis the radiation characteristics of noise from transmission lines were obtained. Those are the directivity of antenna toward the line, lateral profiles, frequency spectra, height pattern and so on.

• Journal of Sensor Science and Technology
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• v.19 no.1
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• pp.1-7
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• 2010

Electrostatic capacitance measurement method in a fine hose was proposed, in which two ring-type electrodes were disposed on the hose in the direction of fluid flow instead of the conventional face-to-face electrodes. With the proposed electrode structure, we realized a Ringer's solution exhaustion detector for an IV(invasive vein) injection set. On a 4 mm-diameter hose of IV set, we disposed two ring-type electrodes of 10 mm width at a distance of 5 mm each other and obtained 0.72 pF and 2.51 pF for air and 10 % dextrose Ringer's solution in the hose, respectively. The capacitance between the two electrodes varied with the hose-wraparound coverage of electrode as well as the width of electrode and the distance between the electrodes. For hose-wraparound electrode coverage of 75 %, the capacitance varied from 0.62 pF to 1.98 pF with the Ringer's solution level between the two electrodes. A charge amplifier converted the capacitance. variation into electric signal and a comparator was used to detect whether Ringer's solution was exhausted or not. The result was delivered to a host using a RF transmitter with 320 MHz carrier frequency.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.205-215
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• 2015

Common mode (CM) conducted interference are predicted and compared with experiments in a motor drive system of Electric vehicles in this study. The prediction model considers each part as an equivalent circuit model which is represented by lumped parameters and proposes the parameter extraction method. For the modeling of the inverter, a concentrated and equivalent method is used to process synthetically the CM interference source and the stray capacitance. For the parameter extraction in the power line model, a computation method that combines analytical method and finite element method is used. The modeling of the motor is based on measured date of the impedance and vector fitting technique. It is shown that the parasitic currents and interference voltage in the system can be simulated in the different parts of the prediction model in the conducted frequency range (150 kHz-30 MHz). Experiments have successfully confirmed that the approach is effective.

• Composites Research
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• v.26 no.6
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• pp.337-342
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• 2013

The good dispersion of nano-materials in epoxy matrix was important parameter for the reinforcement effect, and the evaluation of dispersion degree was to prove it. This work was studied to predict the dispersion condition of nano-SiC powders in SiC/epoxy composites using capacitance measurement. Capacitance was defined to be the electric capacity in proportional to electron charge of the measuring section. In case of nano-SiC powders, the electron charge of SiC/epoxy composites was higher than that of neat epoxy resin. Capacitance was evaluated for each section of SiC/epoxy composites. The prediction of dispersion condition was verified by using capacitance measurement. Dispersion condition of nano-SiC powders in epoxy matrix was evaluated with two different dispersion methods, i.e., sonication and stirring methods. The dispersion degree was also verified with the tensile strength correlating to capacitance.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.5
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• pp.15-21
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• 2011

This paper presents an analyzing method of the capacitance of the power transformer for initial voltage distribution and insulation design. When a high incoming surge voltage is accidently occurred in windings of transformer, it does not distribute equally in the windings. This phenomenon makes electric field concentration and the insulating material could be break. Initial voltage distribute mostly depends on capacitances between winding to winding or winding to core in the transformer. If the C network can be structuralized into the equivalent circuit model and be calculated each capacitance element value by circuit analysis and FEM(Finite Element Method) simulation program, the transformer designer could know the place where the structure is to be modified or the insulation to be reinforced. This method quickly provides the data of the voltage distribution in each winding to the designer.

• Journal of the Korean Chemical Society
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• v.54 no.1
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• pp.93-98
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• 2010

In this work, the electrochemical properties of surface treated multi-walled carbon nanotubes (MWNTs) were studied. Nitrogen and oxygen functional groups of the MWNTs were introduced by urea and acidic treatment, respectively. The surface functional groups of the MWNTs were confirmed by X-ray photoelectron spectroscopy (XPS) measurements and zeta-potential method. The characteristics of $N_2$ adsorption isotherm at 77 K, specific surface area, and total pore volumes were investigated by BET eqaution, BJH method and t-plot method. Electrochemical properties of the functionalized MWNTs were accumulated by cyclic voltammetry at the scan rates of 50 $mVs^{-1}$ and 100 $mVs^{-1}$ in 1M $H_2SO_4$ as electrolytes. As a result, the functionalized MWNTs led to an increase of capacitance as compared with pristine MWNTs. It was found that the increase of capacitance for urea treated MWNTs was attributed to the increase in density of surface functional groups, resulting in improving the wettability between electrode materials and charge species.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.10
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• pp.693-698
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• 1999

Vacuum interrupters have a special asymmetric electrode structure to generate an magnetic field and consequently to increase the interrupting ability. Accordingly 2-dimensional analysis has a large analysis error because radial flux can not be considered. In this paper, in order to analyse the electric field distribution of a vacuum interrupter with arc shield more accurately, 3-dimensional finite element method(FEM) is used. The induced electric potentials of floating shield was increased with the gap distance, which is because the relative position of shield is closer to the fixed contact so that the capacitance distribution inside interrupter is varied. The calculated results also show that the induced potential of shield causes electric field distortion so that the maximum value of electric field in a vacuum interrupter with arc shield is higher than that without one.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.913-915
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• 1998

This paper describes the application of two and three dimensional electric field analysis for vacuum interrupter with spiral contacts. The electric potentials of floating arc shield and electric fields in a vacuum interrupter are analysed at various gap distances from 1mm to 12mm. The electric potentials of floating shield is increased with the gap distance, which is because the relative position of shield is closer to the fixed contact so that the capacitance distribution inside interrupter is varied. The calculated results show that the maximum value of electric field in a vacuum interrupter with floating shield is nearly same to that without shield at short gap distance below 5mm, however at longer gaps more intensive electric field is achieved in interrupter with shield comparing with the model without shield, which is due to the influence of charged floating shield.