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Title: Localised variation of magnetic properties of grain-oriented electrical steels
Author: Xu, Xintong
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2015
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Localised magnetic flux density, magnetising field and power loss are believed to distribute non-uniformly in grain oriented electrical steel. Understanding of the causes of their variation can help reduce the overall power loss of the material. In this investigation, magnetic domain observation was often used in the study of domain configuration and crystal orientation of the test specimens. Methods of domain observation have been studied and compared in order to select the appropriate method for different parts of the investigation and to improve the understanding of the image observed. A less destructive local loss measurement sensor has been built for the measurement of localised flux density, magnetising field and power loss. The sensor was tested and evaluated specifically for the measurement of localised magnetic power loss of the high permeability grain oriented electrical steel. The results obtained from local loss scanning measurements indicated that localised flux density and magnetising field can vary substantially in grain oriented electrical steel under AC magnetisation of 50 Hz. The variation of localised flux density has been found mainly resulted by grain misorientation and local grain arrangement. The transverse component of flux density was detected and has been found increases with increasing grain misorientation. The variation of localised magnetising field has been found mainly influenced by the localised demagnetising field due to formation of free magnetic poles at grain boundaries. It has been proved that both flux density and magnetising field have strong influence on the distribution of localised power loss. The study of the effect of domain refinement on distribution of localised flux density showed that domain refinement by means of ball scribing on one surface of grain oriented electrical steel can improve the uniformity of distribution of flux density. However, results also inferred that excessive scribing in a confined area can cause obvious uneven distribution of flux density in the direction of the specimen’s thickness.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General)