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Two-dimensional magnetisation problems in electrical steels

Zurek, Stanislaw 2005. Two-dimensional magnetisation problems in electrical steels. PhD Thesis, Cardiff University.

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The power losses occurring under two-dimensional magnetising conditions have received a great deal of attention in recent years. They are very important in the three-phase electrical machines, and have been investigated for a long time in order to understand the physical processes and the mechanism of such losses. However, the accuracy of the measurements of rotational power loss is proved to be not sufficient and the differences between clockwise and anticlockwise power losses have been unexplained for many years. A computerised two-dimensional single sheet tester for the measurements of power losses in electrical sheet steel have been developed. A unique adaptive iterative digital feedback algorithm has been developed it allows magnetisation under controlled flux density and magnetic field patterns in wide range of frequency from 1 Hz to 1000 Hz and in various magnetising yokes. A new type of flux density sensor has been proposed and discussed. The experimentation did not confirm theoretical predictions. Further work needs to be carried out on this subject. It was found that the power losses measured in clockwise and anticlockwise direction of rotation differ significantly and that this difference is caused mainly by the angular displacement of the flux density and magnetic field sensors. The error of averaging from clockwise and anticlockwise losses has been estimated and the technique for minimising the difference has been mathematically proposed and implemented for the first time. Also, several factors contributing to the clockwise-anticlockwise loss difference have been discussed and their influence assessed. It has been found that the peak value of power losses measured under controlled flux density or controlled magnetic field patterns differ, and that this difference depends on the anisotropy of the sample. It has been proved that the peak losses for controlled magnetic field might be as much as six times of the losses measured under standardised alternating magnetisation. The quasi-static hysteresis component of power loss has been investigated for a non-oriented electrical sheet steel. Despite very high flux density of 2.0 T the static loss does not drop to zero. At higher frequencies the eddy current component of the total power loss takes over and causes the peak of the power loss characteristic to vanish. The effect is more visible for thick laminations, as expected.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
ISBN: 9781303201301
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Jan 2018 06:18

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