Rotational Magnetization in Transformer Cores-A Review

Usually, rotational magnetization (RM) is associated with rotating machine cores. However, in more restricted ways, it also arises in three-phase transformer cores. Modern designs of T-joint yield detours of flux, as a source of RM in the T-joint, the middle limb ends, as well as in the yokes. Simul...

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Bibliographic Details
Published in:IEEE transactions on magnetics 2011-11, Vol.47 (11), p.4523-4533
Main Authors: Pfutzner, Helmut, Mulasalihovic, Edin, Yamaguchi, Hiroi, Sabic, Damir, Shilyashki, Georgi, Hofbauer, Franz
Format: Article
Language:English
Subjects:
Anisotropic magnetoresistance
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
High definition video
Losses
Magnetization
Magnetostriction
Materials
Materials science
Other topics in materials science
Physics
rotational magnetization
silicon alloys
Transformer cores
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Summary:Usually, rotational magnetization (RM) is associated with rotating machine cores. However, in more restricted ways, it also arises in three-phase transformer cores. Modern designs of T-joint yield detours of flux, as a source of RM in the T-joint, the middle limb ends, as well as in the yokes. Simulation of RM is possible by means of so-called rotational single sheet testers which should consider the large grains of highly grain oriented materials. Their high effective anisotropy yields induction patterns of rhombic or lancet-like type with maximum values of axis ratio a up to 0.5, and very high angular velocity round the materials hard directions. Compared to elliptic RM-as arising in non-oriented materials-the corresponding losses are lower due to restricted induction in the hard direction. But they show strong increase with (i) rising a and (ii) rising angular velocity of the induction vector. The magnetostrictive strain shows a pronounced (negative) maximum in the rolling direction with values up to 10 ppm, the transverse direction and normal direction exhibiting positive maxima of lower extent. With respect to industrial relevance, significant RM effects are restricted to the vicinities of T-joints. They represent the location of maximum core loss and also of maximum magnetostrictive strain as a source of audible core noise.
ISSN:0018-9464
1941-0069
DOI:10.1109/TMAG.2011.2151201