A tentative model for the electrical aging of the insulation of rotating machines

A model for the electrical aging of cable insulation has already been presented by one of the authors. The basic principles of this model were used in an attempt to understand the electrical aging of various rotating machines and electrical motors. Results obtained with different types of insulation (asphalt, polyesters, etc.) and aged under a wide variety of conditions have been used for this preliminary study. It appears that the experimental results of rotating machines aging obey a semi-log relation between the square of the applied field and the log of time, as predicted by our aging model. The slope of such plots is related to the so-called activation volume of the aging process, that is to the stressed volume. The intercept in the semi-log plots is related to the activation energy of the process. These two basic parameters depend on the insulation nature, morphology and on several other parameters - especially temperature. The identification and exact role of these unknown parameters require further work but the fact that the fundamental aspects of our aging model apply to this specific case suggest that it could possibly be possible to use the model for more reliable life prediction for rotating machines. Suggestions for further experimental and theoretical work is briefly discussed.