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ASYNCHRONOUS OPERATION OF SYNCHRONOUS GENERATORS

Date

1975-12

Journal Title

Journal ISSN

Volume Title

Publisher

ORCID

Type

Degree Level

Doctoral

Abstract

If a synchronous generator is allowed to operate asynchronously following a loss of synchronism, it is possible to avoid the complete loss of its capacity. The purpose of this thesis is to critically examine the performance of hydro- and turbo- generators under this abnormal mode of operation. An analytical technique is developed, based on the assumption of operation at a constant slip. The validity of the analysis is tested by using the results of experimental investigations. The analysis is applied for studying the effects of different modes of the field winding connection on the constant as well as pulsating components of the various quantities. The permissible asynchronous power output is evaluated on the basis of the constraints set by the stator and rotor losses, the reactive power demand, the terminal voltage drop, the induced field voltage and pulsations in these quantities. In fact, the slip will be of a pulsating nature because of rotor asymmetries. By means of digital simulation studies, the effects of different modes of the field winding connection on the amplitudes as well as waveshapes of the slip pulsations, while delivering different values of asynchronous power, are investigated. The nature of the various electrical quantities in the presence of slip pulsations is also studied. The results of these studies are compared with the performance characteristics obtained from the constant-slip analysis and the validity of the assumption of a constant slip is discussed. By a logical extension of the constant-slip analysis, the presence of slip pulsations is taken into consideration in terms of a series of harmonic components in the various quantities. A harmonic balance technique is developed for calculating these harmonic components. The results obtained are in good correlation with' those of the digital simulation studies based on the non-linear differential equations of the machine. In the case of turbo-generators, the asynchronous performance will be affected by the eddy currents induced in the solid parts of the rotor. A theoretical analysis is developed in which these currents are represented by a single current sheet in the pole region and three different current sheets in the slotted region. On this basis, an equivalent generator model is obtained in terms of different parameters in the d- and q- axes.

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Citation

Degree

Doctor of Philosophy (Ph.D.)

Department

Electrical Engineering

Program

Committee

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DOI

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