Considerations on the compatibility conditions of the Eyring model applied for multiple stresses

The thermodynamic approach is often used for the life modeling of insulating materials subjected to multiple thermal-electrical stresses. It is pointed out, however, that even if the thermodynamic approach seems quite promising for insulation characterization, care should be taken when it is used to infer material behavior under multiple thermal and electrical stresses. Indeed, at very low electrical stresses or temperatures, life is determined by thermal and electrical aging, respectively, and therefore compatibility conditions should be satisfied. The authors show that compatibility considerations are useful in formulating mathematically correct models of insulation life under multiple stresses