MECHANISMS OF NOISE GENERATION OF MODEL TRANSFORMER CORES

The audible noise of transformer cores is generated by vibrations due to both magnetostriction and magnetic forces which gain relevance in t he case of highly oriented SiFe. The Maxwell stress vector depends str ongly on the flux distribution in the core corners which show maximum dislocations delta(z) normal to the sheet planes. Multi-step-lap assem bling increases delta(z) but reduces harmonic distortions which can be assumed to be one reason for the decrease in A-weighted noise.