9,225 research outputs found
Influence of ac ageing on space charge dynamics in LDPE
No full textPolymeric materials have been widely used as insulation in power industry due to their excellent electrical properties. However, these properties deteriorate in time irreversibly when the material is subjected to electric stress. Although space charge is believed to play an important role in ac ageing, exact mechanisms are poorly understood due to very limited experimental data. In the present work efforts have been made to investigate the influence of ac ageing on space charge dynamics in low-density polyethylene (LDPE). LDPE films with 200mm were aged at 50 kV/mm at 50 Hz for various times at ambient temperature. Space charge dynamics in the samples prior to and after ageing were monitored using the pulsed electroacoustic (PEA) technique under dc electric stress. The results indicate that there is a significant amount of homocharge accumulation in the unaged sample due to charge injection. These injected charges are the captured by the deep traps originated from the interface between crystalline and amorphous regions in LDPE. Ageing under ac condition does not necessarily lead to an increase in amount of charge in the bulk but leads to an increase in mobility of charge carriers. Chemical analysis by infrared spectroscope (FTIR) reveals there are chemical changes taken place in the bulk of the material after ac ageing. It is believed that the chemical changes introduce shallow traps which promote the movement of charge carriers in the bulk. Consequently, the injected charges spread across the sample
A power sharing series power BJT array with isolated low voltage control for AC power control applications
No full textA technique for a continuously variable AC resistance using a series BJT array is presented. This array provides high power dissipation capability and uniform voltage and power distribution across the individual transistors. The array, controlled using a set of optoisolators to maintain the electrical isolation between the control circuits and the power stage, could be used as the basis to develop several useful techniques including a solid state AC regulator with comparable performance to the commonly used ferro-resonant systems; a linear AC electronic load suitable for testing UPS and other power conditioners; and, in other AC power control applications such as switching capacitors in AC resonant circuits
Atlee Phillips Inside IGA Supermarket
No full textIGA employee Atlee Phillips, also known as Dopey Phillips, is shown inside IGA standing among shelves of food. (circa 1965)https://digitalcommons.jsu.edu/lib-ac-histimg/29580/thumbnail.jp
Tommy Phillips, 1953 Sophomore
No full textTommy Phillips was a sophomore at Jacksonville State Teachers College in 1952-1953.https://digitalcommons.jsu.edu/lib-ac-histimg/6255/thumbnail.jp
Words of Remembrance delivered at the State Funeral for The Honourable John Harber Phillips AC QC
No full textHer Honour discusses the professional career of The Honourable John Harber Phillips AC, QC (who served as Chief Justice of Victoria from 1991 to 2003) and comments on His Honour’s many positive contributions to the law, general society and education
Florida Phillips, 1953 Junior
No full textFlorida Phillips was a junior at Jacksonville State Teachers College in 1952-1953.https://digitalcommons.jsu.edu/lib-ac-histimg/6785/thumbnail.jp
Charles Phillips, ROTC Cadre
No full textStaff Sergeant Charles Phillips was an Assistant Instructor MSII at Jacksonville State College (now Jacksonville State University) in 1964-1965.https://digitalcommons.jsu.edu/lib-ac-histimg/33609/thumbnail.jp
Linda Phillips, Student 1
No full textLinda Phillips was a student at Jacksonville State College (now Jacksonville State University) in the mid 1960s.https://digitalcommons.jsu.edu/lib-ac-histimg/12912/thumbnail.jp
Linda Phillips, Student 4
No full textLinda Phillips was a student at Jacksonville State College (now Jacksonville State University) in the mid 1960s.https://digitalcommons.jsu.edu/lib-ac-histimg/12915/thumbnail.jp
Frances Phillips, Student
No full textFrances Phillips was a student at Jacksonville State College (now Jacksonville State University) in 1966-1967.https://digitalcommons.jsu.edu/lib-ac-histimg/18433/thumbnail.jp
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