• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.189-193
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• 1997

(S $r_{0.85}$/C $a_{0.15}$)Ti $O_3$(SCT) thin films at various deposition temperature and rf power were grown by rf magnetron sputtering method on optimized Pt-based electrodes (Pt/TiN/ $SiO_2$/Si). The crystallinity of the films increases with increasing deposition temperature. SCT thin film is depend on the surface morphology and crystallinity of Pt films for bottom electrode. Dielectric constant of (S $r_{0.85}$C $a_{0.15}$)Ti $O_3$ thin films deposited on Si wafer substrate are larger with the increase of deposition temperature and gain size.in size.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.360-363
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• 1997

The method of estimating life time of epoxy composites which be widely used for transformers has been studied in this paper. The breakdown properties of specimens are observed by appling high AC voltage at the room temperature from a series of the experiments. Afterwards, the breakdown time was determined under the constant voltage below the lowest breakdown voltage. Also, V-t properties were found out using weibull distribution widely used in the applications of discrete data for estimating life time of epoxy composites and life exponent n was gained properly. when life exponent is gained is found out, the tong breakdown life time at used voltage can be estimated from breakdown experiments in short time using reverse law of n power.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.3
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• pp.154-160
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• 2004

In this paper, a combined field orientation and adaptive backstepping approach using a sliding mode adaptive flux observer, is proposed for the control of induction motor In order to achieve the speed regulation with the consideration of improving power efficiency, rotor angular speed and flux amplitude tracking objectives are formulated. Rotor flux and inverse time constant are estimated by the sliding mode adaptive flux observer based on a fixed stator frame model and mechanical lumped uncertainty such as inertia moment, load torque disturbance, friction compensated by the adaptive backstepping based on a field-oriented model. Simulation results are provided to verify the effectiveness of the proposed approach.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.238-241
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• 2000

In this paper, we manufactured Pb($Ni_{1/2}$ $W_{1/2}$)$O_3$-Pb($Mn_{1/3}$$Nb_{2/3}$)$O_3$-Pb($Zr_3$Ti)$O_3$ceramics with variation of milling time and investigated its dielectric and piezoelectric properties. Density was increased with the increase of milling time because the sinterability of specimens were improved with the decrease of particle size. The highest value of electromechanical coupling factor was 0.518 at milling time 5hour. The highest values of mechanical quality factor and dielectric constant were 1566, 1590 at milling time 4hour, respectively.

• Journal of Surface Science and Engineering
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• v.29 no.5
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• pp.424-429
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• 1996

Thin films of Ti-Ni alloy were formed by sputtering under various Ar gas pressures and r. f. powers to investigate the optimum sputtering conditions and to demonstrate their shape memory effect. The composition and structure of the films were examined by electron micro-probe analysis and scanning electron microscope. These films were annealed in order to crystallize them. The mechanical property of the annealed films was evaluated by a conventional bending test. The transformation tmeperatures were determined by differential scanning calorimetry. The shape memory behaviour was examined quantiatatively by changing in sample temperature under various constant loads. It was found that the Ar gas pressure had a critical effect on the mechanical property of the thin film,s although the r.f. power also affected it. The films formed at a high Ar gas pressure were too brittle to be bent successfully. However, the films formed at a low Ar gas pressur could be bent and their shape memory behavior was found to be comparable with that of bulk Ti-Ni alloys.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.226-228
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• 2007

SRM drive systems are designed to meet operating standards such as low cost, constant torque independent of rotor position, a desired operating speed range, high efficiency, and high performance. In applications using small motors, low cost and high performance with self-starting capabilities are highly desired. This paper discusses a novel two phase SRM (TPSRM) that has high performance characteristics with self-starting capability, low manufacturing cost with a two phase inverter and simple magnetic structure, and high efficiency. The principle of operation, analysis, and simulation for design are presented. The machine design is verified using finite element analysis (FEA) software. Analysis and simulation results are given to validate the TPSRM design.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.16-18
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• 2007

In this paper, an advanced DTC(Direct Torque Control) scheme for PMSM(Permanent Magnet Synchronous Motor) is presented. The proposed DTC method uses a conventional torque estimator and torque error. But the switching signal is generated by PWM method according to the switching rules and torque error. A simple calculation of PMW without any complex determination of space vector can assure the constant switching frequency with an excellent control performance. The proposed torque control scheme for PMSM is verified by computer simulation.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.417-418
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• 2017

납축전지는 충전특성 곡선에 따라 정전류 충전 구간과 정전압 충전 구간으로 나누어 충전 동작을 수행하는 것이 바람직하다. 그러나 플라이백 컨버터를 사용한 저가형 배터리 충전기에서는 컨버터 회로의 1차측과 2차측의 절연을 유지하면서 이러한 2가지의 제어를 수행하는 것이 기술적으로 어려울 뿐만 아니라 회로가 복잡해지므로 현실적으로는 간편하게 정전압 충전만을 사용하는 경우가 대부분이다. 이처럼 정전압 충전만을 사용하게 되면 납축전지에 큰 충전 전류가 흐를 수 있으므로 축전지의 발열이나 수명 단축 등의 문제를 야기할 수 있다. 본 논문에서는 마이크로컨트롤러에 의해 제어되는 디지털 가변저항을 사용하여 실시간으로 전압 피드백을 조절하는 방법으로 정전류 제어가 가능한 새로운 정전류 및 정전압 충전 방식을 제안하였으며, 직접 실험을 통하여 유효성을 확인하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.46-49
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• 2000

This paper studied development of the program for estimation the life time of insullating materials and the longtime breakdown voltage. First, short-time breakdown voltage of Epoxy and insulating oil was measured. Life exponent was gained from measurement of insulating breakdown time of the specimens. Life time is presumed from program. The estimation program is based on the "Inverse Power Law", defined $V^nt$ is constant. After gaining the life exponent n, it is mapping the longtime breakdown voltages. On the base of life exponent, the estimation the lifetime and usefulness of the insulation systems are possible, furthermore easy calculation is possible.

• Journal of Sensor Science and Technology
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• v.29 no.3
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• pp.180-186
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• 2020

In this study, we applied edge-pulse modulation to prevent the flicker of light-emitting diode (LED) light in a visible light identification system. In the visible light transmitter, positive pulses were transmitted at the edges of the low-to-high transition points, and negative pulses were transmitted at the edges of the high-to-low transition points of the non-return-to-zero (NRZ) data waveforms. In the visible light receiver, the NRZ waveforms were regenerated by making low-to-high and high-to-low transitions at the point of the positive and negative pulses, respectively. This method has two advantages. First, it ensures that the LED light is flicker-free because the average optical power of the LED was kept constant during data transmission in the transmitter. Second, the 120 Hz optical noise from the adjacent lighting lamps was easily cut off using a simple RC-high pass filter in the receiver.