Determination of thermal life of enameled wire by laboratory methods

A THERMAL life test which will give quick results is a desirable feature in wire enamel development. Since it may be necessary to screen many formulations, it is desirable that this test be convenient to run. Four criteria for thermal life determination are briefly reviewed. These are as follows: 1. visual inspection of thermally aged coils; 2. flexibility of aged enameled wire; 3. decrease in film thickness with aging; and 4. dielectric breakdown of aged dielectric twist samples. In each test the enameled wire samples are aged in air-circulating ovens and the life is determined at temperatures of 100 to 300 degrees centigrade (C). Some data obtained from these tests are presented.