Dielectric Breakdown of Polymeric Insulations Aged at High Temperatures

Most of electric insulation materials used in power generation and energy storage are polymeric dielectric materials: winding insulations in power transformers, electric starter/generators, electric actuators, high frequency resonators, and power converters; dielectric films in power capacitors or energy storage devices; encapsulation in electronic components and devices. These polymeric dielectric materials have limited continuous use temperatures because of their electrical properties deteriorating at high temperatures. The temperature dependence and thermal aging effect on their dielectric breakdown are of prime concern for analyzing their failure mechanism to prevent catastrophic breakdown of the power system in aviation and military platforms. In this paper, the thermal aging effect on breakdown strength, mechanical properties and physical features of various polymeric insulations, such as polyimide (PI), polyetherimide (PEI), polyetheretherketones (PEEK), and perfluoroalkoxy (PFA) films, will be presented and discussed.