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다결정 초전도체 ${SmBa_2}{Cu_3}{O_x}$의 자기 이력곡선
이준호,정미숙,이부영,김건철,김영철,정대영,Lee J. H,Jung M. S,Lee B. Y,Kim G. C,Kim Y. C,Jeong D. Y 한국초전도학회 2004 Progress in superconductivity Vol.6 No.1
The polycrystalline superconductor $SmBa_2$$Cu_3$$O_{x}$ is fabricated, and intergranular magnetic properties are investigated using the critical state model, from which some useful parameters such as the critical current density and the intergranular volume fraction are obtained. The curve fitting for M-H hysteresis loop shows that the intergranular critical current density of $SmBa_2$$Cu_3$$O_{x}$ / decreases in the form of ($1-T/T_{c}$ )$^{1.5}$ . The intergranular volume fraction is influenced by granular morphology. From SEM image, the grains of $SmBa_2$$Cu_3$$O_{x}$ are found to be randomly shaped. This mean:; that the intergranular volume fraction of $SmBa_2$$Cu_3$$O_{x}$ / should be smaller than those of superconductors, of which grains are plate-shaped such as Tl-based superconductor.
4스위치 3상 BLDC 전동기의 속도응답특성 향상에 대한 연구
이준호(J.H. Lee),김태성(T.S. Kim),김경화(K.W. Kim),현동석(D.S. Hyun) 전력전자학회 2004 전력전자학술대회 논문집 Vol.- No.-
This paper presents a new speed control method using the acceleration feedforward compensation and using the disturbance torque estimate method. The proposed method improve transition response characteristic of system and has been a robust characteristic in the four-switch three-phase motor drive system in which the gain of speed controller cannot be made large enough. The simulation results prove the validity of the proposed method.