A functional evaluation program was established which will provide a comparison of thermal service life of wire and cable insulation by combining the effects of heat aging with the most predominant service stresses. The stresses are necessarily of greater severity than normal service and thus provide relative life data rather than absolute values of service life. Experimental data of life versus aging temperature when statistically treated and the log of life versus the reciprocal of the absolute temperature plotted on semi-log paper approximates a straight line which can be represented by the Chemical Rate Equation. Temperature cycling studies conducted on a representative magnet wire insulation system indicate that reasonable estimates of service life under varying temperature conditions can be obtained by applying the relative aging factor principle. From the life versus temperature curve a relative aging factor can be derived which can be applied to convert aging time at any given temperature to a relative amount of normal life consumed at a reference temperature. When the high temperature exposures occur in known service cycles, it is possible to calculate the number of cycles of safe operation which can be expected of the cable. Author
Preapred for presentation at the Annual Wire and Cable Symposium (8th), Asbury Park, N. J., December 1, 2, and 3 1959.