Some electromagnetic problems in large conventional and superconducting synchronous generators
Some electromagnetic problems in large conventional and superconducting synchronous generators
The research presented in this thesis was concerned with the study of electromagnetic screening, particularly in superconducting turbogenerators. Several investigations were carried out to determine the effect of screening in different parts of the machine. A simple quasi-static 2-dimensional study of the tubular screens in Chapter 2, representing very simplistically the rotor screen of a superconducting turbogenerator, shows that, in a solely magnetic screening situation, the double screening structure is better for the same space occupied than a single screen. Theoretical results obtained from the program simulating an aluminium (non-magnetic conducting) rotor screen in Chapter 3 are compared with the experimental ones. The screen length must extend beyond the rotor end winding for good screening. This is needed to avoid undue end effect and requires an extra length for the screen equivalent to the screen inner radius. End effects can be reduced by using a helical winding for the stator. The computed results of the core end conducting screen in Chapter 4 give a rough estimate of the power loss on its surfaces, despite the fact that the results lack an accurate match between the field components across the imaginary boundary between the regions. Representation of the major ferromagnetic components of a cylindrical machine as surfaces of magnetic polarity is outlined in Chapter 5. This technique has been called the method of Magnetic Sources and can be applied to the determination of the magnetic field distribution in any air region of the machine except on the highly screened side of the core. The Magnetic Sources Program was used to obtain the flux density results in the non-magnetic regions of two models. The First model, representing a conventional turbogenerator in Chapter 7, considers the effect of changing the rotor core length as well as the field winding length. A slightly shorter rotor core gives us several advantages; the resultant axial flux density in the air gap near the core end is less than before, and hence the eddy-current losses in the end packets of the stator teeth will be less, and there will be a small reduction in the cost of the rotor and the copper losses. The second model, representing a high-temperature superconducting (HTSC) turbogenerator in Chapter 8, shows the effect of the magnetic steel support for the winding. It is clear that the field current required to produce the same open-circuit rated voltage is higher if the rotor steel is reduced. In the extreme case of an ironless rotor, the current must increase nearly eight-fold causing a possible current density increase of as high as 16 times because the superconductor may be required to occupy no more than half the cross-section of a copper conductor.
University of Southampton
Al-Khoury, Ayad Hanna Nasir
1990
Al-Khoury, Ayad Hanna Nasir
Al-Khoury, Ayad Hanna Nasir
(1990)
Some electromagnetic problems in large conventional and superconducting synchronous generators.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The research presented in this thesis was concerned with the study of electromagnetic screening, particularly in superconducting turbogenerators. Several investigations were carried out to determine the effect of screening in different parts of the machine. A simple quasi-static 2-dimensional study of the tubular screens in Chapter 2, representing very simplistically the rotor screen of a superconducting turbogenerator, shows that, in a solely magnetic screening situation, the double screening structure is better for the same space occupied than a single screen. Theoretical results obtained from the program simulating an aluminium (non-magnetic conducting) rotor screen in Chapter 3 are compared with the experimental ones. The screen length must extend beyond the rotor end winding for good screening. This is needed to avoid undue end effect and requires an extra length for the screen equivalent to the screen inner radius. End effects can be reduced by using a helical winding for the stator. The computed results of the core end conducting screen in Chapter 4 give a rough estimate of the power loss on its surfaces, despite the fact that the results lack an accurate match between the field components across the imaginary boundary between the regions. Representation of the major ferromagnetic components of a cylindrical machine as surfaces of magnetic polarity is outlined in Chapter 5. This technique has been called the method of Magnetic Sources and can be applied to the determination of the magnetic field distribution in any air region of the machine except on the highly screened side of the core. The Magnetic Sources Program was used to obtain the flux density results in the non-magnetic regions of two models. The First model, representing a conventional turbogenerator in Chapter 7, considers the effect of changing the rotor core length as well as the field winding length. A slightly shorter rotor core gives us several advantages; the resultant axial flux density in the air gap near the core end is less than before, and hence the eddy-current losses in the end packets of the stator teeth will be less, and there will be a small reduction in the cost of the rotor and the copper losses. The second model, representing a high-temperature superconducting (HTSC) turbogenerator in Chapter 8, shows the effect of the magnetic steel support for the winding. It is clear that the field current required to produce the same open-circuit rated voltage is higher if the rotor steel is reduced. In the extreme case of an ironless rotor, the current must increase nearly eight-fold causing a possible current density increase of as high as 16 times because the superconductor may be required to occupy no more than half the cross-section of a copper conductor.
This record has no associated files available for download.
More information
Published date: 1990
Identifiers
Local EPrints ID: 462551
URI: http://eprints.soton.ac.uk/id/eprint/462551
PURE UUID: 7d782583-5cc8-4243-b0a1-09018883d003
Catalogue record
Date deposited: 04 Jul 2022 19:19
Last modified: 04 Jul 2022 19:19
Export record
Contributors
Author:
Ayad Hanna Nasir Al-Khoury
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics