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Title: A novel method of measurement and characterisation of magnetostriction in electrical steels
Author: Anderson, Philip
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2000
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Magnetostriction has been shown to be a major contributor to transformer noise. This is particularly true in regions of increased stress within the core of these machines since the magnetic properties of grain oriented silicon steel are extremely sensitive to applied stress. A novel system has been developed for the measurement of the harmonics of magnetostriction under applied stress. The system, the first of its kind to be fully automated, is capable of rapidly and repeatably measuring power loss and permeability simultaneously with magneto stricti on. Miniature accelerometers are used to measure the vibrations of a strip of electrical steel and a feedback controlled pneumatic system applies stresses ranging from 10MPa to -10MPa. The rapid nature of this system allowed a large sample of material to be taken from a wide range of grain oriented silicon steel which led to several important advances. A previously unreported effect whereby the thickness of the steel strip was seen to be directly proportional to its peak magnetostriction under applied compression was observed which was explained as being due to the increasing relative volume of transverse domain structure. Previously reported coating models were enhanced to allow the calculation of the stresses applied by two separate coatings as well as the additional stresses retained by these coatings. The coating stresses were found to be directly proportional to the thicknesses of each of the coatings. The measured harmonics of magnetostriction were seen to agree well with a theoretical model.
Supervisor: Moses, A. J. ; Stanbury, H. J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available