How to calculate the mechanical stress in insulation paper of transformer windings resulted from electromagnetic force under rated operating condition and other fault conditions?
I will give you only some guide lines: First, review magnetostriction in some ferromagnetics materials texbook; calculate the change on shape due to magnetic filed over ferrous material, which depends on the original shape, material properties, field magnitude and relative direction with regard to the core body. Second step, add the paper envelope and calculate how much elongation will it suffer, due to the shape change, before it breaks, which depends much more in how much tight it embraces the transformer body than in paper elasticity, if any. Besides, could the paper produce mechanically any amount of core shape restoration? That depends one core elasticity properties.
Thank you for your answer! I am sorry, maybe I didn't express clealy before. I just want to calculate the mechanical stress on the insulation paper which twines around the surface of the copper conductor in the oil-immersed transformer, when the electromagnetic force acts on the copper conductor under rated operating condition and other fault conditions. Do you understand? Can you give me some suggestions about how to built the model. It is the problem of coupling of machanical and electromagnetic field.
Can you access the following article: Electrostriction: Nonlinear Electromechanical Coupling in Solid Dielectrics
R. E. Newnham,V. Sundar,*, R. Yimnirun,J. Su, and, and Q. M. Zhang; The Journal of Physical Chemistry B 1997 101 (48), 10141-10150 DOI: 10.1021/jp971522c ?
It is not specific about insulating paper, but may be is closer to that you are looking for.
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