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이병하(B.H. LEE),김진성(J.S. KIM),차한주(H. CHA) 전력전자학회 2009 전력전자학술대회 논문집 Vol.2009 No.1
본 논문은 수백 ㎲의 펄스폭과, 수십 kA 전류량을 갖는 펄스전원모듈의 메인스위치로 광 싸이리스터(Light Triggered Thyristor ; LTT)를 적용하기 위해 수행한 스위칭 특성에 관한 논문이다. 광 다이오드의 출력 펄스 가변에 대한 턴 온 특성, 순방향 인가전압 변화에 대한 스위칭 지연 특성, LTT 직렬 운용 시 전압분배 특성, 대전류 통전 능력 및 di/dt 능력 특성 등을 실험을 통해 확인 하였다.
광섬유 브래그 격자 변형률 센서용 현공진기의 고정밀 측정
이영균(Y. K. Lee),송인천(I. C. Song),정성호(S. H. Jeong),이병하(B. H. Lee),이선규(S. K. Lee) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.9
This paper describes a string resonator that is used for the interrogation system of a Fiber Bragg Grating (FBG) strain sensor. The strain on the fiber piece is calculated from the measured frequency based on that the natural frequency of a string is a function of the applied absolute strain. Existing research considered a fiber as a string, but a fiber is not a string in the strict sense due to its bending stiffness, thus the fiber should be modeled as a beam accompanied with an axial force. In the vibration modeling, the relationship between the strain and the natural frequency is derived, and then the resonance condition is described in terms of both the phase and the mode shape for sustaining resonant motion. Several experiments verify the effectiveness of the proposed model of the fiber. The performance of the string resonator is analyzed by measuring the frequency change according to the applied strains in the dynamic range of 1100με referred to the displacement from capacitance sensor. From the experimental results, the implemented string resonator provides the accuracy of ±3με, the quasi-static resolution of ~0.1 με(rms) which amount to be ±0.17㎛ and -6㎚ respectively, in case of fiber length of 56㎜. For a dynamic strain, it can provide the accuracy of -3με until the frequency comes to 8㎐. As a consequence, the string resonator proposed for FBG sensor provides the high accuracy and the high resolution in strain measurement, and also it is expecting to be used, for the application, to not only strain but also displacement measuring device.