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The basis is presented for a more accurate interpretation of the results of physical type tests to measure the thermal aging of insulation together with a more accurate method of applying the results of such tests to predicting insulation deterioration in practice. Since the observed physical changes during thermal aging are the result of internal chemical changes in organic material, it is shown that the theory of chemical reaction rates can be applied to analyze experimental data on aging. The approximate 7 to 10 rule for the temperature coefficient of deterioration rate is replaced by a more accurate theoretical expression. Various examples of insulation life tests are analyzed using the graphical methods outlined in the paper. The chemical rate theory interpretation of thermal aging offers a more satisfactory method for extrapolating the results of limited aging tests of insulating materials so they can be applied to predicting amounts of thermal aging in high temperature cycles.
American Institute of Electrical Engineers, Transactions of the (Volume:67 , Issue: 1 )
Date of Publication: Jan. 1948