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Brushless Doubly-Fed Reluctance Machines for Aerospace Electrical Power Generation Systems

Duke, Alexander (2015) Brushless Doubly-Fed Reluctance Machines for Aerospace Electrical Power Generation Systems. PhD thesis, University of Sheffield.

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Abstract

This thesis describes a programme of research encompassing the design, optimisation and experimental testing of a brushless doubly fed reluctance machine (BDFRM) for use as an aerospace electrical generator, specifically a direct line connected generator, to widen the input shaft speed beyond the normal constraints imposed by the 360-800Hz specification for a variable-frequency AC aerospace network. BDFRMs offer the functionality of frequency correction, via a control winding, and have the advantage of using a robust reluctance rotor. A partially-rated control winding converter can, in principle, be used to provide the slip power required. A further advantage of the BDFRM is the inherent fail-safe nature of these machines, with the output voltage collapsing as soon as the control winding current has been removed. A synchronous reluctance machine was studied as a means of providing a baseline for the BDFRM performance, including a comparison of the effect of scaling on power density. A large number of time-stepped finite element simulations were undertaken to explore BDFRM performance, in particular, the influence of magnetic saturation in limiting the achievable power density and in compromising power quality. Detailed optimisation of a BDFRM was undertaken, including systematic mechanical design of the rotor for high speed operation. This analysis illustrates the significant compromises in machine electromagnetic performance which result from the need to accommodate mechanical stress. The scope for employing small amounts of permanent magnet material in the rotors of both synchronous reluctance machines and BDFRMs, to improve the machine performance at the lower end of the current density range, was investigated. Following detailed optimisation, a demonstrator machine was manufactured, which includes a skewed rotor. The performance of this machine was measured at a number of test points to verify predictions of output power, voltage and voltage harmonics.

Item Type: Thesis (PhD)
Academic Units: The University of Sheffield > Faculty of Engineering (Sheffield) > Electronic and Electrical Engineering (Sheffield)
Depositing User: Mr Alexander Duke
Date Deposited: 03 May 2016 10:44
Last Modified: 03 May 2016 10:44
URI: http://etheses.whiterose.ac.uk/id/eprint/12228

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