Ontario Hydro experience with generator rotor forging cracks at the winding slot tooth roots

This paper describes the experience of Ontario Hydro with rotor forging cracks in the winding slot tooth roots of several of its 500 MW generators. A summary is provided regarding; how the cracks were discovered, crack similarities between rotors, crack initiation and propagation theories, crack growth rate estimates, limiting factors, NDE techniques developed to find and size existing cracks, vibration monitoring for crack propagation, and the final results of the crack investigations.