• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.10
• /
• pp.464-468
• /
• 2003

The double layers of $SiO_2$/$Si_3$$N_4$ have superior charge storage stability than a single layer of $SiO_2$. Many researchers are very interested in the charge storage mechanism of $SiO_2$/$Si_3$$N_4$ [1,2]. In this paper, the electrical characteristics of thermal oxide and atmospheric pressure chemical vapor deposition (APCVD) of $Si_4$$N_4$ have been investigated and explained using high frequency capacitance-voltage measurements. Additionally, this paper will describe capacitance-voltage characteristics for double layers of $SiO_2$/$Si_4$$N_4$ by "Athena", a semiconductor device simulation tool created by Silvaco, Inc.vaco, Inc.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.1 s.232
• /
• pp.87-94
• /
• 2005

A computer code for Electrical Capacitance Tomography (ECT) is developed to sense the cross sectional phase distribution of two-phase flow in the rectangular pipe in which the tomography sensor furnished by the insulated wall, electrodes, and electric field screen. The computer code had two steps for the image reconstruction. In the forward projection step, the sensitivity matrix was constructed based on the electric field calculated by the finite difference method. In the backward projection step, the sensitivity matrix and the measured capacitances were used to reconstruct the cross sectional image. Several algorithms including LBP, TR, ITR, and PLI were employed to find the proper one for the two-phase flow analysis. Since the dielectric constant of the water in two-phase flow is sensitive to the thermal parameter such as, temperature and pressure, the developed code was evaluated to find their accuracy, speed of calculation, and sensitivity to the variation of the dielectric constant. It was found that the iterative methods are superior to the direct methods for the image reconstruction, and the PLI method was the best in the variation of the dielectric constants.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.44 no.12
• /
• pp.1610-1616
• /
• 1995

The (Sr$_{1-x}$ .Ca$_{x}$)TiO$_{3}$(0.05.leq.x.leq.0.2) ceramics were fabricated to form semiconducting ceramics by sintering at about 1350[.deg. C] in a reducing atmosphere (N$_{2}$ gas). After being fired in a reducing atmosphere, metal oxides, CuO, was painted on the both surface of the specimens to diffuse to the grain boundary. They were annealed at 1100[.deg. C] for 2 hours. The 2nd phase formed by thermal diffusing from the surface lead to a very high apparent dielectric constant. The results of the capacitance-valtage measurements indicated that the grain boundary was composed of the continuous insulating layers. The capacitance is almost unchanged below about 20[V], but decreased slowly over 20[V]. The conduction mechanism of the specimens observed in the temperature range of 25~125[.deg. C], and is divided into three regions having different mechanism as the current increased: the region I below 200[V/cm] shows the ohmic conduction. The region II between 200[V/cm] and 2000[V/cm] can be explained by the Poole-Frenkel emission theory, and the region III above 2000[V/cm] is dominated by the tunneling effect.ct.

• Transactions on Electrical and Electronic Materials
• /
• v.13 no.4
• /
• pp.181-184
• /
• 2012

$BaTiO_3$ based multilayer ceramic capacitors with Ni electrodes can be explained as 2-2 composites with different thermal expansion coefficient and sintering behaviors. To achieve the high capacitance and reliability of MLCCs, a homogenous Ni electrode configuration with high connectivity is required. We controlled the heating rates during sintering to achieve densification by suppressing grain growth. Experimental results revealed that a large heating rate gave high connectivity of Ni electrode, high capacitance, small dissipation factor, high breakdown voltage, and high reliability of MLCC chips.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.42-42
• /
• 2009

To make up for the disadvantages of PVA gate, we blend PVP(20% wt) with PVA(5% wt) as a gate material. The best ratio for the mixture was 5:5, PVP-PVA blended gate used MIM structure showed better performance in leakage current and capacitance. PVP-PVA blended gate was fabricated by spin-coating process and pentacene was used as an organic TFT channel layer by thermal evaporation. Overall OTFT performance has also increased as PVP-PVA blended gate has relatively lower leakage current and higher capacitance than pure PVA gate has.

• Journal of Magnetics
• /
• v.1 no.2
• /
• pp.94-100
• /
• 1996

A hysteresis loop tracer using a pulsed high magnetic field of 113.4 kOe, which is suitable for rare earth based permanent magnets, is constructed. The high pulsed magnetic field is generated by discharging a large capacitance charge (5 mF) with a voltage of 600 V into an air solenoid with the inner diameter of 14 mm, outer diameter of 36 mm and the lingth of 34 mm. A computer simulation method is used for the construction of an electromagnet to optimize the many parameters such as the discharge current, generated pulsed magnetic field intensity, thermal dissipation, capacitance, charged voltage, period of damping oscillation and solenoid geometry. By using the hysteresis loop tracer constructed in this work, we are able to measure hystersis loops of several rare earth based permanent magnets with large values of the remanent magnetization, coercvity and energy product.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.88-88
• /
• 2010

High Voltage cross-linked polyethylene (XLPE) cables are widely used in a thermal power plant. These cables had been in service for 26 years. The insulation condition of six 6 kV XLPE cables was estimated by insulation diagnostic analyzer (IDA) with voltage amplifier. IDA was measured dissipation factor and capacitance of the whole cable as a function of frequency and voltage. This system measures in the frequency range from 0.1 to 10 Hz at each voltage level. Six XLPE cables are judged good condition, but three cables are analyzed at an aged condition.

• Proceedings of the KIEE Conference
• /
• 2002.07c
• /
• pp.1452-1454
• /
• 2002

Large turbine generator(rated 22kV) has failed in the stator winding area during normal operation. The capacitance and tan${\delta}$ were measured by Schering bridge in the zone 1, 2 and zone 3-6 stator windings. The capacitance and tan${\delta}$ in the zone 1, 2 of stator winding were higher than those of zone 3-6 in the stator winding. Experiments on microstructure property were conducted in the zone 1, 2 and zone 3-6 insulations, which were drawn out from stator windings of the large turbine generator. Microstructure analysis was characterized using scanning electron microscope(SEM). SEM results indicated that several isolated delaminations occurred at the interface of mica/epoxy insulations. Both thermal and mechanical aging cause the delamination.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.49-53
• /
• 2006

In this paper the thermal aging characteristics of transformer fluid were considered. First, the temperature rise characteristic in transformer winding was discussed. The temperatures were rapidly increased immediately with applying load and then the temperature was followed the exponential temperature rise model. Next, Capacitance and leakage current characteristics of the transformer fluid were measured during the over-loading operation. The capacitance of vegetable fluid and leakage current were evidently increased wit aging time. So the simple methods could be applied to diagnosis of the transformer aging

• Transactions of the Korean hydrogen and new energy society
• /
• v.26 no.2
• /
• pp.184-191
• /
• 2015

As the power electronics system increases the frequency, the power loss and thermal management are paid more attention. This research presents a real time model of dissipation power with junction temperature response for 120kw IGBT inverter which is applied to the thermal management of high power IGBT inverter. Since the computational time is critical for real time simulation, look-up tables of IGBT module characteristic curve are implemented. The power loss from IGBT provides a clue to calculate the temperature of each module of IGBT. In this study, temperature of each layer in IGBT is predicted by lumped capacitance analysis of layers with convective heat transfer. The power loss and temperature of layers in IGBT is then communicated due to mutual dependence. In the dynamic model, PWM pulses are employed to calculation real time IGBT and diode power loss. Under Matlab/Simulink$^{(R)}$ environment, the dynamic model is validated with experiment. Results showed that the dynamic response of power loss is closely coupled with effective thermal management. The convective heat transfer is enough to achieve proper thermal management under guideline temperature.