Generators have been widely used in a variety of applications including aircraft, automobiles and turbines. Generators typically include a stator and a rotor that work together to produce electricity. Wind turbines have received increased attention recently as an environmentally safe alternative energy source. Wind turbines convert the kinetic energy of the wind into mechanical power and then the mechanical power drives the generator to produce electricity.
Offshore wind turbines typically have ratings of 3MW and higher, necessitated by the economics of wind energy production. Also offshore turbines employ a direct drive generator to improve reliability, unlike most land based utility scale wind turbines that utilize a geared generator. These ratings and the fact that the generator is directly driven manifests into a very large size and weight. A machine greater than 4 m in diameter is difficult and costly to transport by conventional means and necessitates segmentation. While the segmented stator structures facilitate cost and transport, particularly when designed to accommodate conventional rail or road shipping constraints, they are difficult to manufacture and assemble at site.
In order to reach high power density, the stator core requires a certain level of cooling through the stator laminations. Stator assemblies typically have spacers or inside space blocks located at certain axial locations between two adjacent laminations. These spacers are repeated after a nominal axial distance and provide a radial flow path for a cooling medium. While the spacer blocks provide for a gas flow path for stator cooling, they are limited in their ability to provide structural support to the stator or stator segment, particularly for very large stator assemblies.
For these and other reasons, there is a need for the present invention.