Date of Award
Fall 2004
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Electrical and Computer Engineering
First Advisor
Demerdash, Nabeel A. O.
Second Advisor
Brown, Ronald H.
Third Advisor
Povinelli, Richard J.
Abstract
The harmonic effects arising from non-linearity in transformer winding inductances when such transformers are connected to controlled rectifier systems feeding adjustable speed dc motor drives or other dc loads are presented in this thesis work. These harmonic effects are studied primarily on the basis of comparison of the effects of magnetic saturation in the core of the transformer, on the ac side of systems consisting of such transformers connected to controlled rectifiers feeding adjustable speed dc motors. Earlier works on this subject have largely ignored these magnetic saturation effects by considering only the effects of fundamental components of flux in the transformer core, and therefore the inductances of the cores of these transformers have generally been represented as constant parameters. This thesis work also goes beyond this comparison by attempting to bring to light the effects of failing to take into account the heating of the core of the transformer due to hysteresis losses. However, a study of these effects that takes into account energy losses in the transformer core due to hysteresis is beyond the scope of this work. In order to study these non-linearity effects, the transformer is modeled first, as a device in which the winding inductances vary from one point in time to another in an ac cycle and, second, as a device with a constant winding inductance. The entire transformer-controlled rectifier dc motor system is modeled in the Pspice software environment, which is a very convenient environment for simulating complex models of electric machines and drives systems. It is easy to include the full representation of the transformer winding inductance variation from one point in time to another in an ac cycle using Pspice-based circuit models. Additionally, the use of Pspice software where discrete parameter circuit systems can easily be represented, avoids the headache of having to write complex computer codes to simulate such systems. The case study in this work is a single-phase 1.5kV A shell-type transformer that is feeding a 2-hp separately excited dc motor through a controlled rectifier system. The varying inductance profiles needed as data for the Pspice simulation are obtained from the analysis of the magnetic saturation in the core of the transformer by means of the well-known method of Finite Element Analysis. The simulation results obtained in both cases are then compared to test results obtained by running the actual experimental setup in the laboratory.
Recommended Citation
Sesay, Ahmed Ibrahim, "Study of the Harmonic Effects Due to Transformer Magnetic Nonlinearities in Controlled Rectifiers Feeding Adjustable Speed DC Motor Drives" (2004). Master's Theses (1922-2009) Access restricted to Marquette Campus. 4168.
https://epublications.marquette.edu/theses/4168