• The Transactions of the Korean Institute of Power Electronics
• /
• v.22 no.3
• /
• pp.185-192
• /
• 2017

This paper proposes a single-stage interleaved soft-switching electrolytic capacitor-less EV charger with reduced component count and simple circuit structure. The proposed charger achieves ZVS turn-on of all switches and ZCS turn-off of all diodes without regard to voltage and load variation. It achieves high power density even without an input filter due to CCM operation and bulky electrolytic capacitors and without a low-frequency component in the transformer. A 2 kW prototype of the proposed charger with sinusoidal charging is built and tested to verify the validity of the proposed operation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.232-233
• /
• 2007

We manufactured Liquid Crystal Polymer (LCP) and (1-x)CaTiO3-xLaAlO3 (CT-LA) ceramic composites and investigated dielectric properties to use as embedded capacitor in printed circuit boards and replace LTCC substrate. The dielectric properties of these composites are varied with volume fraction of CT-LA and ratios of CT/LA. Dielectric constants are in the range of 3~15. In addition, we could get low TCC and High Q value that could not achieve in other ceramic-polymer composites. Especially, in composite with x=0.01 and 30 vol% CT-LA, the dieletric constant and Q-value are 10 and 200, respectively. And more TCC is $-28{\sim}300ppm/^{\circ}C$ in the temperature range of $-55{\sim}125^{\circ}C$. We think that this composites can be used high-Q substrate material like LTCC and embedded temperature compensation capacitor in printed circuit boards.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.4
• /
• pp.190-194
• /
• 2017

Present-day solar panels incorporate inverters as their core components. Switching devices driven by specialized power controllers are operated in a transformerless inverter topology. However, some challenges associated with this configuration include the absence of isolation, causing leakage currents to flow through various components toward ground. This inevitably causes power losses, often being also the primary reason for the power inverters' analog equipment failure. In this paper, various aspects of the leakage currents are studied using different circuit analysis methods. The primary objective is to convert the leakage current energy into a usable DC voltage source. The research is focused on harvesting the leakage currents for producing circa 1.1 V, derived from recently developed rectifier circuits, and driving a $200{\Omega}$ load with a power in the milliwatt range. Even though the output voltage level is low, the harvested power could be used for charging small batteries or capacitors, even driving light loads.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.53 no.3
• /
• pp.122-128
• /
• 2004

This paper presents a control approach for designing a fuzzy-PI controller for a synchronous generator excitation and SVC system. A combination of thyristor-controlled reactors and fixed capacitors(TCR-FC) type SVC is recognized as having the most flexible control and high speed response, which has been widely utilized in power systems, is considered and designed to improve the response of a synchronous generator, as well as controlling the system voltage. A Fuzzy-PI controller for SVC system was proposed in this paper. The PI gain parameters of the proposed Fuzzy-PI controller which is a special type of PI ones are self-tuned by fuzzy inference technique. It is natural that the fuzzy inference technique should be based on humans intuitions and empirical knowledge. Nonetheless, the conventional ones were not so. Therefore, In this paper, the fuzzy inference technique of PI gains using MMGM(Min Max Gravity Method) which is very similar to humans inference procedures, was presented and applied to the SVC system. The system dynamic responses are examined after applying all small disturbance condition.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.7
• /
• pp.1311-1315
• /
• 2016

Induction motor requires a rotating magnetic field for rotation. Current required to generate the rotating magnetic field is immediately magnetizing current. This magnetizing current is associated with the reactive power. Induction motor is always required reactive power. If reactive power is supplied only to the power supply side, the power factor is low. Therefore, it is to compensate the power factor by connecting capacitors in parallel to the motor terminal. If the capacitor current is greater than the magnetizing current of the motor, there is a possibility that the self-excitation occurs. High voltage generated by the self-excitation leads to insulation failure on the motor. So it is necessary to calculate the power factor correction capacitor capacity the most suitable to the extent that the magnetizing current does not exceed the capacitor current. In this study, we first computed the magnetization current and the reactive power of the induction motor and then calculates a limit of the maximum power factor by comparing the magnetizing current and the capacitor current installed in order to achieve the target power factor.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.65 no.3
• /
• pp.158-164
• /
• 2016

In this paper, a high frequency flyback type zero voltage soft switching PWM DC-DC converter using IGBTs is proposed. Effective applications for this power converter can be found in auxiliary power supplies of rolling stock transportation and electric vehicles. This power converter is basically composed of active power switches and a flyback high frequency transformer. In addition to these, passive lossless snubbers with power regeneration loops for energy recovery, consisting of a three winding auxiliary high frequency transformer, auxiliary capacitors and diodes are introduced to achieve zero voltage soft switching from light to full load conditions. Furthermore, this power converter has some advantages such as low cost circuit configuration, simple control scheme and high efficiency. Its operating principle is described and to determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and compared with the hard switching PWM DC-DC converter from an experimental point of view and the comparative electromagnetic conduction and radiation noise characteristics of both DC-DC power converter circuits are also depicted.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.71-74
• /
• 2000

Pt/Pb$TiO_3$/$SrTiO_3$/p-Si films were prepared by metallo-organic solution deposition(M0SD) method and investigated its structure and ferroelectric properties. Crystallinity of specimen as a funtions of post annealing temperature and the thickness of $SrTiO_3$(STO) buffer layer was studied using XRD and AFM. Based on C-V and P-E curve, $PbTiO_3$(PTO) capacitors showed good ferroelectric hysteresis arising from the polarization switching properties. When the thickness of ST0 buffer layer between PTO and Si substrate was 260 nrn and the post annealing temperature was $650^{\circ}C$, it was showed that production of the pyrochlore phase due to interdiffusion of Si into FTO was prevented. The dielectric constant of FTO thin films calculated from a maximum Cma in the accumulation region was 180 and the dielectric loss was 0.30 at 100 kHz frequency. The memory window in the C-V curve is 1.6V at a gate voltage of 5V.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.12 no.1
• /
• pp.56-61
• /
• 1999

Highly conductive oxide films of BaRuO$_3$ have been grown heteroepitaxially on (100) LaAlO$_3$ single crystalline substrates by using pulsed laser deposition. The films are c-axis oriented with an in-plane epitaxial relationship of <010><100>BaRuO$_3$ // <110>LaAlO$_3$. Atomic force microscopy (AFM) observation shows that they consist of a fine-arranged network of grains and have a mosaic microstructure. Generally temperature-dependent resistivity shows the transition from metallic curve to semiconductor-metallic twofold curve by the deposition conditions for Ru oxide based materials like SrRuO$_3$, CaRuO$_3$, BaRuO$_3$, etc.. This twofold curve comes from the structural similarity of Ru oxide based materials including BaRuO$_3$. We find that the distance of Ru-Ru bonding in the unit cell of BaRuO$_3$ as well as the grain boundary scattering could be the two important causes of these interesting conductive properties.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.33-36
• /
• 1999

In this paper, $Ba_{0.5}$Sr$_{0.5}$TiO$_3$ thin-films were prepared on Pt/Ti/Si0$_2$/Si substrates by RF magnetron sp-uttering method. We investigated electric and dielectric properties of BST thin-films with various ann-ealing temperature using in-sute RTA. Deposition conditions of BST films were set substrate temperat-ure, 30$0^{\circ}C$ and working gas ratio, Ar:O$_2$=90:10. After BST films deposited, we fabricated a capacitor of MIM structure with Al top electrode for measurement. Post-annealing using RTA performed at 40$0^{\circ}C$, $600^{\circ}C$, 80$0^{\circ}C$ for 60 sec, respectively. Also we exacted crystallization and composition of BST thin-films by XRD analysis. In measurement result, this capacitors showed a dielectric constant of about 200 at 1MHz and leakage current density of 5$\times$10$^{-8}$ A/$\textrm{cm}^2$ at 1.5V Microstructure of BST thin-films exhibited effective quality in low-temperature annealed 71ms than high-temperature annealed 71ms.s.s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.157-159
• /
• 2005

MOS capacitors were fabricated to study electrical and chemical properties of Ta-Mo metal alloy with $ZrO_2$. The work function of Ta-Mo alloy were varied from 4.1eV to 5.1eV by controlling the composition. When the atomic composition of Mo is 10%, good thermal stability up to $800^{\circ}C$ was observed and work function of MOS capacitor was 4.1eV, compatible for NMOS application. But pure Ta exhibited very poor thermal stability. After $600^{\circ}C$ annealing, equivalent oxide thickness of tantalum gate MOS capacitor was continuously decreased. Barrier heights of Ta-Mo alloy and pure metal that supported the work function values were calculated from Fowler-Nordheim analysis. As a result of these electrical?experiments, Ta-Mo metal alloy with $ZrO_2$ is excellent gate electrode for NMOS.