System for providing uniform axial expansion of a stator core

Abstract

A system for ensuring uniform axial expansion of a dynamoelectric machine's stator core subjected to elevated temperatures. The stator core constitutes axially adjacent ferromagnetic laminations held in axial compression by through-bolts axially extending through an intermediate portion thereof and building bolts situated in notches formed in the radially outer periphery of the laminations. The building bolts are secured to bore rings which circumferentially encircle and provide support for the stator core. The bore rings are rigidly secured in the axial direction by structural members connected to the bore rings and surrounding machine frame. Nuts disposed on each axial end of the through-bolts are torqued to allow at first axial expansion of the core while maintaining a selected degree of axial compression of the laminations during operation at elevated temperatures. Thermal axial expansion of the building bolts is restrained by their securement to the bore rings and the bore rings' axial securement to the dynamoelectric machine's frame. A spring is disposed on each axial end of the building bolts between the laminations and a building bolt nut. Suitable selection of the spring's force constant and tightening torque for the building bolt nuts permits a second axial expansion of the lamination's outer periphery which is at least as great as the first axial expansion of the lamination's intermediate portions. Uniform axial expansion of the lamination portions between the outer periphery and intermediate portion is provided by a rigid core support plate radially disposed between and intersected by the through-bolts and building bolts.