In PPPL's campaign to improve operating efficiency and reduce operating costs of our large vertical shaft motor generators proved to be a fruitful area. The measured losses in the stator air cooling loop were in the area of one megawatt. Reducing these losses was the focus of a recent study by PPPL and GE Hydro. Operating data was used to calculate the load cycle temperature profile of the motor generator. Based on the wide margin between design limitation and operating profile the estimated energy saving is about 200 KW per hour. An optimum air velocity through the generator stator cooler was determined and means were developed to reduce the flow without compromising generator insulation limits.

*Work supported by U.S. DOE Contract DE-AC02-76-CHO3073.