• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.5 no.4
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• pp.69-74
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• 1991

전력용 MOSFET를 사용한 새로운 PAM-PWM 인버터를 제안한다. 제안된 PAM-PWM 인버터의 출력파형을 이론과 실험적으로 연구했다. 선간전압파형은 기본파성분과 캐리아 주파수의 사이트벤드로 집중되어 저차 고주파는 출력파형에 포함되지 않았다. 각 인버터 아암은 2/3주기 동안 동작하지 않음으로 소자의 발열도 줄어든다. 그러므로 방열판의 감소에 의하여 인버터 시스템의 크기도 작아진다.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2482-2487
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• 2007

Numerical simulations are conducted for the analysis of a thermal mass air flow sensor with periodic heating pulses on silicon-nitride ($Si_3N_4$) thin membrane structure. This study aims to find the locations of temperature sensors on the thin membrane and the heating pulse conditions, that the higher sensitivity can be achieved, for the development of a MEMS fabricated mass air flow sensor which is driven in periodic heating pulse. The simulations, thus, focus on the membrane temperature profile according to variation of the flow velocity, heating duration time and imposed power. The flow velocity of the simulations is ranging from 3 m/s to 35 m/s, heating duration time from 1 ms to 3 ms and imposed power from 50 mW to 90 mW. The corresponding Reynolds numbers vary from 1000 to 10000.

• Fire Science and Engineering
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• v.34 no.4
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• pp.1-6
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• 2020

In this study, the authors measured voltage and current waveforms in real time during a serial arc discharge. The analysis results of the arc discharge radiation patterns exhibited intermittent discharge, arc growth, creation of a heat generating area, occurrence of plume, and formation of a red heat area, which proceeded in that order. When the serial arc discharge was introduced, the current and voltage waveforms exhibited periodicity as sine waves. It was also observed that a restriking transient voltage occurred when the waveform changed from positive (+) to negative (-) and vice versa. When the discharge proceeded, the amount of heat generated for 1 s and 600 s was approximately 0.317 mJ, and 190 mJ, respectively. The duration of the short circuit was approximately 1.66 ms, and in the case of the voltage waveform, it was evident that the electric potential increased to 49.9 V in the same cycle. Furthermore, when the discharge proceeded, the effective value (RMS value) of the current was approximately 1.72 A with a maximum current of approximately 2.53 A, whereas the effective value of the voltage was approximately 42.8 V with a maximum of approximately 208 V.