Electromagnetic forces in sheet-and foil-wound transformers

A detailed calculation is presented of both axial and radial components of the electromagnetic forces developed in foil-wound transformers. The actual distribution of current along the length of the foil and the presence of iron core are taken into consideration. The axial forces transferred to the end supports and the case of asymmetrical windings are also calculated. Attention is focused upon the effect introduced by the nonuniform distribution of current in the windings. A mathematical model is set up for the general case, where both the transformer windings are of foil and asymmetrically placed relative to the yokes. Transformers having various combinations of foil-wound, wire-wound and sectionised windings are included within the general analysis. The practical scope for the application of the method is illustrated by typical examples.