Alternator rotor cracking problems and their solutions

Heysham nuclear power station has two 660 MW turbogenerators manufactured by NEI Parsons. The rotor is an alloy steel forging with field winding slots cut along the full length of the round rotor body. In January 1988 a rotor of similar type to Heysham´s operating at Drax was taken out of service and found to have a major crack. During September a second rotor at Drax was also found to have a major crack. The author looks at maintenance and inspection techniques used at Heysham to make sure that the same cracking does not occur