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Title: Magnetostriction and magnetic anisotropy in non-oriented electrical steels and stator core laminations
Author: Somkun, Sakda
ISNI:       0000 0004 2750 9835
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2010
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Magnetostriction is a source of vibration and acoustic noise of electrical machines and it can be highly anisotropic even in non-oriented electrical steel. Understanding of magnetostriction under magnetisation and stress conditions present in stator core laminations can help predict the core vibration and radiated noise. Anisotropy of magnetostriction of a 0.50 mm thick non-oriented steel investigated in Epstein strips cut at angles to the rolling direction was much higher than the anisotropy of its magnetic and elastic properties because magnetostriction arises directly from magnetic domain processes. Magnetostriction of a disc sample of the 0.50 mm thick steel was measured under ID and 2D magnetisation and compared with that of a 0.35 mm thick steel with different anisotropy level. A 2D magnetostriction model and an analytical simple domain model were used to explain the experimental results. 2D magnetostriction is dependent on the magnetostrictive anisotropy and the ratios of the transverse to longitudinal magnetostriction. AC magnetostriction measured in the disc samples was larger than in the Epstein strips due to the form effect. An induction motor model core was constructed from the 0.50 mm thick steel for measurements of localised flux density and deformation. Core deformation due to Maxwell forces was calculated. Magnetostriction and specific power loss of the core material under magnetisation conditions present in the core was measured. The localised loss in the stator teeth, tooth roots and back iron differed from their average value by 52%, 19% and 36% due to the magnetic anisotropy. Magnetostriction was estimated to be about 55% and 80% of the radial deformation at the tooth root and back iron regions respectively. Stator teeth deformed asymmetrically and the magnitude of the space harmonics increased due to the magnetostrictive anisotropy. The measurement results inferred that 2D magnetostriction can be predicted from the magnetostrictive anisotropy and vice versa. Also, core deformation and vibration of large machines, where segmented stator core laminations are used, can be estimated analytically with the knowledge of 2D magnetostriction of the core material.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TK Electrical engineering. Electronics Nuclear engineering