Title :
Some aspects of effects of longitudinal and normal stress on power loss and flux distribution within a transformer core
Author :
Joslin, P.C. ; Moses, A.J. ; Thompson, J.E.
Author_Institution :
University of Wales Institute of Science & Technology, Wolfson Centre for Soft Magnetic Materials, Cardiff, UK
fDate :
6/1/1972 12:00:00 AM
Abstract :
An experimental 1.0 m Epstein square has been constructed in which all the limbs could be flattened to 1.5Ã105 N/m2 and two opposite limbs could be stressed longitudinally to ±13.8Ã106 N/m2 Power-loss measurements were made on cores of 46-grade and 56-grade grain-oriented silicon-iron subjected to combinations of longitudinal and normal stress. The power loss (at 1.5 T) increased by only about 10% owing to the normal compression, but linear stress increased the loss by up to 40% (at 9.65Ã106 N/m2 compression). When the applied linear stress was greater than about 5.8 à 106 N/m2, the normal stress restricted the power-loss increase. The effect of normal stress on a 45° mitred-overlap and a double-overlap joint were investigated. In the double-overlap joint, the flux did not deviate from the rolling direction of the laminations. Airgaps in the mitred-overlap joint and the length of the overlap were both found to have a pronounced effect on the corner loss. The lower-loss-grade material was found to have a lower stress sensitivity of power loss to both normal and longitudinal stress.
Keywords :
alloys; losses; magnetic cores; magnetic properties of substances; transformer magnetic circuits; alloys; flux distribution; grain oriented silicon steel laminations; losses; low power loss; magnetic cores; magnetic properties; magnetostriction; stress; transformer magnetic circuit;
Journal_Title :
Electrical Engineers, Proceedings of the Institution of
DOI :
10.1049/piee.1972.0149