Waved core lamination techniques on large and bulb hydroelectric machinery

A waved lamination technique is presented that reduces the tangential and radial spring constant of the core of a large-diameter synchronous machine. The core and frame stresses due to heat expansion differences are reduced. The buckling is completely prevented because of the lower tangential stress. The core, having many built-in waves, absorbs the tangential heat expansion evenly distributed in the waves, without permanent deformations. The change of wave height due to heat expansion is small compared to the buckling in the conventional cores. By choosing different combinations of wave height, wave length, lamination, thickness, axial pressure, etc., it is possible to influence widely the natural frequencies of the core