Abridgment of forces in turbine generator stator windings

Abstract

Experience has shown that the forces on turbine generator armature windings during short-circuit conditions are large, and that if adequate consideration is not given to the design of the coil bracing and support, windings may be seriously damaged. In this paper the forces are calculated for a particular case by the use of images, the change of flux interlinkages, and by the ∫ H2 ds over some surface in air which surrounds the conductor under consideration. A new and relatively simple proof is given for the validity of the latter method, the limitations and desirable applications of each method being considered. Forces on conductors in armature slots are computed with saturation both considered and neglected. Approximate formulas are derived for the forces on coil sides within one layer of the conical end winding, and for the straight coil extensions from the slots, with a numerical example given for each of these cases. The applicability of certain of these formulas to the phase connecting rings is pointed out, and the force on the entire conical surface of the end winding discussed qualitatively. Certain desirable features of end winding bracing are mentioned, in most of these cases the instant considered being that following a line-to-neutral short circuit when the maximum possible instantaneous current is flowing.