A two dimensional study of some eddy-current problems occuring in large electrical machine rotors
A two dimensional study of some eddy-current problems occuring in large electrical machine rotors
This thesis is concerned with calculating eddy-currents which are induced in the solid rotors of large synchronous generators during periods of abnormal operation. The rotors of such machines are manufactured from large forgings of saturable magnetic material. As a consequence a method which deals with the magnetic nonlinearity of the rotor iron has been developed. The work has been restricted to two dimensions, the rotor being assumed to be infinitely long and homogeneous in the axial direction. Magnetic hysteresis of the iron parts has been ignored. A study of typical faults has revealed that an analysis of fixed fundamental (or twice fundamental) frequency, fixed excitation, steady-state problems provides valuable information on these faults. The method and mathematical models employed have been developed and justified for problems of this type. The performance of the developed method has been examined and some indications as to its best use suggested.Moat of the important variables which it is possible to studywith a model of the radial-circumferential plane of the machine have been isolated and their effect examined using both linear and nonlinear models. From this study it is possible to indicate changes in the design which will result in increased capability of the machine to withstand the abnormal operating conditions which cause the induction of significant eddy currents in the rotor.The computed losses have been used to compare directly with tests on a full size machine. They have also been used to compute temperatures which have been compared to temperature measurements made during the tests. The comparison between measured and calculated results has allowed, to some extent, substantiation of the computations. It has also allowed some further analysis of the performance of machines of this type when operating under the examined form of asynchronous operation. Some preliminary work has been done on the use of complex surface impedances, gained from one-dimensional solutions, to model conducting regions in two dimensions. The accuracy of such representations has been examined by comparing the solutions gained with fully represented conducting regions. The behaviour on the surface of nonlinear conducting regions has also been examined to see how closely these conditions match those that would have been assumed if one-dimensional surface impedance theory had been used.
University of Southampton
1977
Jack, Alan Galloway
(1977)
A two dimensional study of some eddy-current problems occuring in large electrical machine rotors.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis is concerned with calculating eddy-currents which are induced in the solid rotors of large synchronous generators during periods of abnormal operation. The rotors of such machines are manufactured from large forgings of saturable magnetic material. As a consequence a method which deals with the magnetic nonlinearity of the rotor iron has been developed. The work has been restricted to two dimensions, the rotor being assumed to be infinitely long and homogeneous in the axial direction. Magnetic hysteresis of the iron parts has been ignored. A study of typical faults has revealed that an analysis of fixed fundamental (or twice fundamental) frequency, fixed excitation, steady-state problems provides valuable information on these faults. The method and mathematical models employed have been developed and justified for problems of this type. The performance of the developed method has been examined and some indications as to its best use suggested.Moat of the important variables which it is possible to studywith a model of the radial-circumferential plane of the machine have been isolated and their effect examined using both linear and nonlinear models. From this study it is possible to indicate changes in the design which will result in increased capability of the machine to withstand the abnormal operating conditions which cause the induction of significant eddy currents in the rotor.The computed losses have been used to compare directly with tests on a full size machine. They have also been used to compute temperatures which have been compared to temperature measurements made during the tests. The comparison between measured and calculated results has allowed, to some extent, substantiation of the computations. It has also allowed some further analysis of the performance of machines of this type when operating under the examined form of asynchronous operation. Some preliminary work has been done on the use of complex surface impedances, gained from one-dimensional solutions, to model conducting regions in two dimensions. The accuracy of such representations has been examined by comparing the solutions gained with fully represented conducting regions. The behaviour on the surface of nonlinear conducting regions has also been examined to see how closely these conditions match those that would have been assumed if one-dimensional surface impedance theory had been used.
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Published date: 1977
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Local EPrints ID: 459738
URI: http://eprints.soton.ac.uk/id/eprint/459738
PURE UUID: 6e985a46-7a12-40ee-a45f-544912ac9c4e
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Date deposited: 04 Jul 2022 17:17
Last modified: 04 Jul 2022 17:17
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Author:
Alan Galloway Jack
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