THEORETICAL AND EXPERIMENTAL INVESTIGATIONS ON RESONANT FREQUENCIES AND NATURAL RESPONSE OF STATORS OF ELECTRICAL MACHINES
Date
1978-02
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ORCID
Type
Degree Level
Doctoral
Abstract
Accurate assessment of values of resonant frequencies and natural response of stators is essential for the purpose of acquiring a quiet operation of electrical machines. In this thesis, an analysis of a general nature is developed for the determination of values of resonant frequencies and natural response of stators of encased construction. The derived frequency equation is applicable to all modes of vibration and can deliver information about all possible resonant frequencies of a stator. The analysis is based on the three-dimensional theory of elasticity; and it is capable of delivering information about not only the radial vibrations of stators but also about the torsional and axial vibrations.
Simplified frequency equations are also derived from the general frequency equation for the special cases of uniform vibrations along the stator circumference and along the stator length.
In order to examine the validity of the analysis, extensive experimental investigations were carried out on nine different models which represent stators of small, medium, and large electrical machines. The comparisons made between the experimental and the analytical results prove the general validity of the analysis. The experimental results also confirm the actual existence of several important phenomena predicted by the analysis. These are the phenomenon of dual resonance, the phenomenon of coupling between components of displacement, and the phenomenon of multiple resonances.
The thesis also presents a fundamental experimental study of the manner in which values of resonant frequencies, amplitudes of vibration and frequency response of stators at resonance are affected by the dynamics of teeth, windings, frame, and laminations. The findings of this study would be helpful for proper incorporation of the effects of teeth, windings, frame, and laminations in the process of accurate determination of resonant frequencies and natural response of stators. The physical interpretations of the results given in the thesis would also help in acquiring a better understanding of the vibration behavior of stators in relation to the problem of electromagnetic acoustic noise in electrical machines.
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Degree
Doctor of Philosophy (Ph.D.)
Department
Electrical Engineering