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H. Pfützner, G. Shilyashki, E Mulasalihovic:
"Modern transformer cores - 3-dimensional magnetic systems of under-estimated complexity";
International Journal of Applied Electromagnetics and Mechanics, vol 48 (2015), no 2,3; 143 - 151.

In contrast to clear under-estimations through non-experts, modern transformers represent high-tech products of highest economic value. This is also true for the soft magnetic core of a transformer. It consists of highly grain oriented (HGO) silicon iron that is surface-treated by stress coating and laser scribing, yielding domain refinement through most intelligent physical mechanisms. Considering a single individual core package, it reveals a complex 2-dimensional flux distribution that is characterized by "flux along rails" due to the high effective anisotropy of HGO materials. It impedes effective numerical modelling since being linked with non-linearity, hysteresis and stress effects from surface treatments. Experimental modelling faces problems of scaling-down and from imperfect clamping, but it yields clear indications for the existence of significant rotational magnetization that should be restricted through further research. The core packages are in - non-clarified - interaction to each other which means that a core has to be considered as a 3D system. This complicates attempts of modelling in further ways. However, high potential exists for further core improvements with respect to lower building factor and lower audible noise. The challenge will be to reduce both characteristics in synchronous ways.

Transformer cores, silicon iron, flux distributions, anisotropy, 3-D effects

http://dx.doi.org/10.3233/JAE-151980