No description available.

No description available.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 99-101). Also available via the Internet.

Inaug.-diss.--Frankfurt-am-Main. / Lebenslauf. "Literaturverzeichnis:" p. 39.

Thesis (Ph.D.) - University of Queensland, 2003. / Includes bibliography.

Thesis (M.S.)--University of Wisconsin--Madison, 1967. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

Orientador: José Pissolato Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T01:29:05Z (GMT). No. of bitstreams: 1 Malaquias_PauloEduardo_M.pdf: 3237738 bytes, checksum: d302a1f85a6963a1f7102598ea519fa6 (MD5) Previous issue date: 2013 / Resumo: Neste trabalho são descritos os mecanismos de envelhecimento do sistema isolante de transformadores papel-óleo mineral, com foco na degradação causada pela presença de umidade no interior dos transformadores. Com o propósito de verificar a degradação do sistema isolante foram executados ensaios em campo e em laboratório. Nos ensaios em laboratório foram retiradas amostras de óleo de treze transformadores de potência em operação e realizados ensaios de envelhecimento acelerado, com separação dos ácidos de baixa e alta massa molar. O objetivo foi correlacionar os ácidos de baixa massa molar com o envelhecimento do isolamento sólido. Os ensaios em campo foram feitos em dez transformadores e visaram verificar a relação da umidade no papel/ papelão isolante com a ocorrência de descargas parciais no interior desses transformadores. Os ensaios de envelhecimento acelerado mostraram a existência de correlação entre o envelhecimento do papel isolante e o teor dos ácidos de baixa massa molar presentes no óleo isolante. Já com os resultados dos ensaios em campo não foi possível comprovar a existência de relação entre umidade no isolamento sólido e descargas parciais no transformador / Abstract: This paper describes the aging mechanisms of the mineral oil-paper insulation system of transformers, focusing on the degradation caused by the presence of moisture inside the transformers. To verify the degradation of the insulation, tests were carried out in the field and in the laboratory. For the laboratory tests, oil samples were taken from thirteen power transformers in operation and accelerated aging tests were conducted. Low and high molecular weight acids were separated from these oil samples in order to correlate the low molecular weight acids with the solid insulation aging. Field tests were conducted in ten transformers and aimed to investigate the relationship between moisture in paper insulation and the occurrence of partial discharges inside the transformer. Accelerated aging tests have shown the correlation between the insulation paper's aging and the content of low molecular weight acids present in the oil. One having the results of the field trials, it was not possible to prove the existence of a relationship between moisture in the solid insulation and partial discharges in transformer / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

D.Ing. / Transformer design is an art which spans a century. Although the basic transformer has changed little over this period, the challenges that face high frequency power transformer designers today have grown considerably. Increasing frequency and power density and decreasing size and profile are among the most important. Eddy currents, controlling circuit behaviour and minimising losses are important aspects of design, and close attention is paid to heat removal and cooling. Modern transformers are no longer limited to certain shapes and sizes; choosing the topology and optimising the shape is often part of the design process. For each aspect of design, numerous modelling techniques exist for analysing transformer behaviour, with varying degrees of complexity. A common feature of optimisation techniques is the large number of variables and interdependent functions that relate different aspects, from the associated behavioural models, to one another. In this study, this complexity is reduced by integrating the individual analytical models for transformer behaviour. Since a convenient thermal model for high frequency transformers does not exist at present, a new thermal reference model is devised and verified. It is specifically suited to high frequency transformer applications and design, and practical sets of reference data are provided for a few ferrite materials and for copper. Transformer losses are considered next, with special attention given to eddy current analysis techniques. New formulations of eddy current solutions are given, with extensions of the orthogonality principle for skin- and proximity effects and superposition thereof. An investigation of leakage impedance design as a function of frequency scaling follows. The relationship between leakage reactance voltage drop as a function of frequency scaling by dividing a monolithic transformer into distributed elements is considered, and the results are applied to two case studies of a 35kVA transformer for a plasma burner application. A new model, the generic proportionality model, applies the thermal referenCe model to scaling of transformer parameters. A case study is also presented, demonstrating the relationships that exist between design parameters and performance functions. Another generic model, the scant model, is introduced, which integrates the thermal reference model into optimisation of transformer shape. It uses a limited number of functional and form parameters, and is applicable to a wide variety of geometries. Two case studies, demonstrate the effects of varying the shape of a rectangular configuration on derating factors.