Lifetime of Machines Undergoing Thermal Cycling Stress

In modern applications, electrical machines are facing increasing thermal cycling and resulting mechanical stress due to harsh variable loading, however there is little information in literature that shows the impact of severe cycling conditions on insulation health. An accelerated aging test is performed in this paper on seven motor stator samples that are operated under various thermal cycling conditions at high temperature. It is shown that there is a severe but predictable lifetime decrease with increased thermal cycling stress. The impact of this must be considered at the design stage for applications requiring high temperature cycling to ensure fulfillment of the required lifetime.