• Smart Structures and Systems
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• v.33 no.4
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• pp.281-290
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• 2024

This work investigates the mechanical energy harvesting from smart and adaptive devices using magnetic interactions. The energy harvester is built from an elastic beam connected to an electric circuit by a magnetostrictive material that promotes energy transduction. Besides, magnetic interactions define the system stability characterizing multistable configurations. The adaptiveness is provided by magnets that can change their position with respect to the beam, changing the system configuration. A mathematical model is proposed considering a novel model to describe magnetic interactions based on the single-point magnet dipole method, but employing multiple points to represent the magnetic dipole, which is more effective to match experimental data. The adaptive behavior allows one to alter the system stability and therefore, its dynamical response. A nonlinear dynamics analysis is performed showing the possibilities to enhance energy harvesting capacity from the magnet position change. The strategy is to perform a system dynamical characterization and afterward, alter the energetic barrier according to the environmental energy sources. Results show interesting conditions where energy harvesting capacity is dramatically increased by changing the system characteristics.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.9
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• pp.1219-1226
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• 2014

This paper introduces a hardware simulator for the LVRT operation analysis of the grid-tied PMSG wind power system with a power dissipation circuit. The power dissipation circuit, which is composed of chopper and resistor, suppresses the sudden increase of DC-link voltage in the back-to-back converter of the grid-tied PMSG wind power system. The LVRT operation was first analyzed using computer simulations with PSCAD/EMTDC. A wind power simulator including the power dissipation circuit and the fault simulator composed of variac and IGBT were built to analyze the LVRT operation. Various experiments were conducted to verify the effectiveness of the power dissipation circuit for the LVRT operation. The developed hardware simulator can be extensively utilized for the analysis of various LVRT operations of the grid-tied wind power system.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.650-652
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• 2001

The permanent magnet in hybrid step motor is magnetized to the axial direction. Accordingly the 2D analysis method such as 2D finite element method cannot guarantee the analysis accuracy. In this paper, the characteristics of hybrid type step motor are analyzed by using 3D equivalent magnetic circuit network method(3D EMCNM). 3D EMCNM supplements magnetic equivalent circuit by numerical technique using distributive magnetic circuit parameter and 3D EMCNM is used for the accurate and efficient analysis. The validity of the analysis results is confirmed by comparing with the experimental ones.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1603-1605
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• 1994

Recently, Gas Circuit Breakers are rapidly replacing Vacuum Circuit Breakers in the medium voltage switchgear. This is due to the improved performance of - GCB in interrupting capability, price, weight, size etc., while the countermeasure to suppress the switching surges of VCB has not been satisfactory. Intensive research works on the GCB have been conducted in the world widely since 1980. Nowadays it is well known that the thermal expansion type GCB can provide- better performance than puffer type in the distribution power system. KERI has conducted researches in the GCB rated at 25.8kV 25kA with Jinkwang Co. using the thermal expantion principle since 1993. In this paper, the calculated results of electric and magnetic fields for the model GCB are presented and analyzed. The effect of permanent magnet used to improve the interruption capabilty at the low current level is also investigated. The design parameters for the interrupter inspected through the short-circuit tests conducted at high power laboratory of KERI.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.971-975
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• 2005

In this study, a car-door-controlled collision protection system using proximity sensor is proposed and its preliminary analysis and several preliminary experiments are conducted. The proposed system has three additional sub-components on the car-door that is, a pair of extra electro-magnetic actuator that are attached to the sliding bar of the open/close car-door four-bar mechanism, a proximity sensor that would be attached to the outside surface of the door which is likely to frequently contact to the object and a driving control circuit of the whole system. A proximity sensor is used to detect object close to the car-door, the driving control circuit provides actuating power command to the electro-magnets to generate braking force to stop the swing motion of the car-door. It is verified through kinematic analysis of the four-bar car-door open/close mechanism and through experiments that the magnitude of maximum electronic magnetic force could provide the braking force enough for this application. For this purpose, an electro-magnet driving circuit is implemented and tested. And also to increase the safety of the system a time delay circuit is implemented and tested.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.57-61
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• 2007

We designed and fabricated square coils of 4 layered structure on a PCB board. The size of the coils were $1{\times}1cm^2\;and\;$2{\times}2cm^2$. The line width of the fabricated coils was $100{\mu}m$. By reciprocating a magnet on the surface of a fabricated square coil which is composed of 4 layers, an alternating output voltage was obtained. We changed the vibrational frequency from 0.5 to 7 Hz. The generated voltages were 62 mV at $1{\times}1cm^2$ and 245 mV at $2{\times}2cm^2$ when 5.5 Hz frequency. We rectified and stepped up the output voltage using a quadrupler circuit and $2{\times}2cm^2$ coil. Before using the step up circuit, the measured voltage was 320 mV at 7 Hz. After using the step up circuit, the measured voltage was 400 mV at 7 Hz.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.7
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• pp.450-455
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• 2015

For the practical application of a YBCO superconductor bulk, the superconductor bulk magnet with high magnetic field on a large area surface should be fabricated. To make this, YBCO single crystal bulks with fine $Y_2BaCuO_5$(Y211) particles have been prepared by the top-seed melt growth(TSMG) method with $YBa_2Cu_3O_x$, $Y_2O_3$, and $CeO_2$ mixing precursor. By using $Y_2O_3$ instead of $Y_2BaCuO_5$ as precursor, the manufacturing process became simpler and more economical. The microstructures, trapped field and critical current density of the various conditioned YBCO bulks have been observed, analyzed and measured. The different characteristic values of the several samples have been analyzed from the viewpoint of their microstructures. We have developed a $8{\times}12cm$ size superconductor bulk magnet, up to 3 T class, by using the 4 T class-high field superconducting magnetizer and confirmed the applicability of the transmission level circuit breakers by measuring the strength and speed of the superconductor bulk magnet actuator.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.818-819
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• 2011

본 논문은 가변자속 기능을 가지는 Flux Switching Permanent Magnet (FSPM) 전동기의 전 자기적 등가회로를 이용한 특성해석방법을 다룬다. 우선 가변자속 기능을 갖는 FSPM 전동기의 구조와 동작원리를 설명하였다. 다음으로 오버행을 고려한 2-D유한요소 해석 모델을 이용하여 역기전력, 인덕턴스를 구하였다. 마지막으로 등가회로 해석을 통해 가변자속 운전 시 FSPM 전동기의 특성해석을 실시하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2179-2183
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• 2007

In this paper, to produce sheet plasma with high density for ion plating, we designed magnetic circuit of ion plating device consisting of solenoid coil and rectangular permanent magnet. And, we analyzed the effects of the magnetic field distribution using FEM (Finite Element Methode). Additionally, we made a sputtering system including ion plating technique on the basis of the design and verified the possibility of the sheet plasma application for advanced sputter system.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.717-718
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• 2015

전동기를 설계 시 자기등가회로법은 전동기의 세부 형상에 크게 구애를 받지 않기 때문에, 공간고조파법과 수치해석기법에 비해 유용하다. 이 논문에서는 Spoke type PMSM(Permanent Magnet Synchronous Motor)의 회전자 자기등가회로를 설계하였다. 회전자 자기등가회로를 통해, 마그네틱 토크 성분을 구성하는 공극자속밀도 수식을 이끌어 낼 수 있다. 이를 통해, Spoke type PMSM은 마그네틱 토크가 주 토크이기 때문에, 공극 자속밀도 및 형상치수비를 이용하여 전동기의 크기를 계산하였다.