Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). "October 2008." Includes bibliographical references (p. [171]-178). Also available via the World Wide Web.

The work presented in this thesis contributes to the understanding of the dynamic behaviour of large power transformer windings under short circuit forces. A simple yet accurate method of prediction of electromagnetic forces is developed and used as input to the dynamic mechanical model. In develop- ing this model the mechanical properties of oil-impregnated pressboard have been investigated and measured in a specially designed rig which simulates the typical power transformer environment. Assumptions have been made regarding these properties to enable them to be meaningfully incorporated in a dynamic model of a transformer. Predictions made using the model have been compared with actual measurements on a transformer and a correlation within 20%-30% was achieved. The work demonstrated the importance of mechanical prestress to ensure that no serious nonlinearities will be encoun- tered in the mechanical behaviour when short-circuit forces are present in a power transformer. It was also found that for small radial deflections, the axial and radial behaviours are independent. This work provides a theoreti- cal basis for further work in which precise determinations of the mechanical properties of oil-impregnated pressboard can be used to model the dynamic behaviour of a large transformer to a high degree of accuracy.

No description available.

The exponentially tapered, nonuniform transmission' line, applied as an impedance transformer, is analyzed and modified. The analysis develops an expression for the input reflection coefficient that has the magnitude and phase as distinct functions. This allows ease in comparing the approximate and exact solutions and in developing the S-parameters for the taper. The modification is a slight change in the taper's shape that yields a significant reduction in the passband reflection coefficient (a tapered line is an impedance-transforming, high -pass filter) with only a slight increase in the taper's length. This modification is accomplished without sacrificing the exponential line's simple, closed-form expressions for both the reflection coefficient and the variation of impedance along the taper. These expressions are subjected to experimental verification. / Graduation date: 1975

Thesis (Ph.D.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Feb. 1, 2010). Bibliography: leaves 195-202.

No description available.

Efficiency is always of great concern in the designs of machines. This factor reflects the amount of savings of energy that can be achieved from a particular design. When thinking of long-term uses, evaluation on the applications of higher efficiency machines will result in giving more visible savings of energy. Transformers are examples of such machines that are used extensively to distribute electricity, and in practice, major losses are produced from their cores and windings, these are called core losses and copper losses respectively. / This research is concerned with efficiency improvement of conventional transformers. Attempts have been made by using two configurations of windings that are made switchable. One of these configurations is chosen at one time on the basis of the secondary current. This is based on the theory that, by implementing higher numbers of turns at low load and fewer numbers of turns at high load than conventional transformers have, total losses that are the sum of core loss and winding loss will be less than total losses produced by conventional transformers. / Thesis (MEng(ElectricalEngineering))--University of South Australia, 2001.

Thesis (M.S. in electrical engineering)--Washington State University, May 2008. / Includes bibliographical references (p. 169-171).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 76-79). Also available via the Internet.

Thesis (Ph. D.)--Johns Hopkins University. / Biographical sketch. Reprinted from the Bulletin of the Bureau of standards, vol. 7, no. 3, 1911. Bibliography: p. 473-474. Includes bibliographical references.