Forces in Turbine Generator Stator Windings

Experience has shown that the forces on turbine generator armature windings during short-circuit conditions are large. The windings may be seriously damaged if adequate consideration is not given to the design of the coil bracing and support. In this paper the forces are calculated for a particular case by the use of images, by the change of flux interlinkages, and by the ∫ H² d s 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 are considered. Forces on conductors in armature slots are computed when saturation is considered, and when 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. A numerical example is given in each of those cases. The applicability of certain of these formulas to the phase connecting rings is pointed out. The force on the entire conical surface of the end winding is discussed qualitatively. Certain desirable features of end winding bracing are mentioned. In most of these cases, the instant considered is that following a line-to-neutral short circuit when the maximum possible instantaneous current is flowing.