PRODUCTION OF SHAFT-VOLTAGES IN TURBOGENERATORS WITH PARTICULAR REFERENCE TO STATIC EXCITATION
Date
1985-06
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ORCID
Type
Degree Level
Masters
Abstract
Exciters using solid-state devices have almost replaced the conventional type rotating exciters in modern large turbogenerator units. The use of static exciters has introduced a special kind of shaft-voltage in turbogenerators. 'This results in currents which damage the machine components such as bearings, seals, gears, etc., by arcing, pitting and oxidation, resulting in outages of generating units.
In this thesis, the causes, the mechanism of production of shaft-voltages and the damages caused by the resulting currents in turbogenerators are discussed. In order to explain the phenomenon of shaft-voltage caused by static exciters in particular, experimental investigations were carried out in the laboratory. The investigations presented in this thesis were done in several stages and were based on field measurements on large turbogenerators. In the course of investigations, equivalent circuit models were developed in order to explain the mechanism of the actual production of the shaft-voltage due to static excitation.
Various investigations on transient skin-effect are discussed with particular reference to the problem of shaft voltage in synchronous machines. An important relationship exists between transient skin-effect and shaft-voltage phenomena. It is found that skin-effect plays a key role in the production of the shaft-voltages of high magnitudes in large synchronous machines.
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Degree
Master of Science (M.Sc.)
Department
Electrical Engineering