Stray Losses in the Armature End Iron of Large Turbine Generators [includes discussion]

The results of a study of stray load losses in the armature end iron of large turbine generators are presented. These losses are induced by the generator end leakage flux, and the resulting end iron temperatures limit the machine capability in the underexcited region of operation. Quantitative methods of analysis of the magnetic field distribution at the ends of the machine and the resulting losses and temperature rise are presented. Design innovations for reducing end iron losses and temperature in both conventional and direct-cooled generators are described. The results of factory and field tests supporting the principal conclusions are included.