M. Tech. Electrical Engineering. / Discusses the placement of windings in the slots of high phase order induction machines (HPOIMs) leads to a stepped-like waveform of stator (rotor) MMFs which exhibit space harmonics as well as the fundamental wave. The interaction of air-gap field components, which have the same pole number but rotate at different speeds, produce the torque ripple whose magnitude depends on the product of the magnitude of the two interacting fields. The frequency of the torque ripples also depends on the difference between the speeds of these two fields. A winding configuration or a combination of different configurations that reduces some air-gap components has the edge in terms of mitigating the ripple torque contents.

The electromagnetic behavior of magnetic devices used in power electronics circuitry, is studied in order to predict their performance within a context of desirable circuit parameters. Past efforts have focused on simplifications widely used in electric machinery applications. Due to the greatly increased operating frequencies of today's circuits (in the upper kHz and lower MHz region), the operation and design of magnetic components greatly differs from those of 60 Hz machinery. A set of models based on assumptions that are unique to the these devices used in power electronics are put forth. The entire approach is based on deriving models from solutions of the field equations, rather than using older, less accurate circuit analogies. More importantly, models are needed for accurate design and optimization processes of complete power electronic systems, in which the magnetic components form a small part. Solutions are sought without using the popular simplifications at very low and very high frequencies, since they are not accurate at intermediate frequencies encountered in power electronics. The conductors used in transformers and inductors are modelled in these high frequency regions. / Ph. D.

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This thesis proposes innovative methods to extract information embedded in the frequency and time domain response of the transformer winding, and utilizes them to suggest solutions to a few tasks that have until now been thought difficult, if not impossible, to resolve. Pursuing this philosophy originated from the basic under- standing that the response of any physical system (behaving largely as a linear time invariant system) has embedded information that characterizes it completely. So, the prerequisite is to evolve ways to extract this information from measured responses. Once that is done, a variety of interesting applications can be envisaged. The two applications considered in this thesis are- •Investigate indirect measurement of the series capacitance of a transformer winding using the measured frequency or time domain response •Explore the possibility of increasing the physical resolution of the ladder network used to model a fully interleaved-disk winding In the former application, since direct measurement of series capacitance is impossible, alternatives based on indirect measurement were also not attempted. Similarly, in the latter application, the upper limit is known to be fixed by the number of distinctly observable peaks in the magnitude frequency response, so the question of increasing this limit was also never explored. Solutions to these tasks are proposed after a systematic analysis of frequency/time domain responses of a winding, initially modeled as a lumped parameter ladder network, to extract correlations that exist between them and winding parameters, and finally examine how these relations can be exploited together with the measured responses. Each of the five chapters is dedicated to describe the solution to one task. In each chapter, analytical formulation is presented first, followed by experimental results. Good agreement with the predicted results demonstrates its practicability. In final summary, indirect measurement of the series capacitance of a winding and en- hancing physical resolution of a ladder network model to represent a fully interleaved- disk winding was successfully demonstrated and they are the main contributions of this thesis.