Multistress Aging of Stator Bars in a Three-Phase Model Stator Under Load Cycling Conditions

The aging characteristics and the life expectancy of stator bar insulating systems are examined under load cycling conditions in a three-phase model stator, such as can arise with frequent start/stops of generators in service. It is demonstrated that the rate of stator bar insulation deterioration, when subjected simultaneously to electrical, mechanical, and thermal stresses, is influenced by the number of load cycles and magnitude of the temperature swings between the full- and zero-load conditions.