A-C and D-C voltage endurance behavior of mica insulation

The voltage endurance of insulation on machine windings is of considerable interest to both manufacturers and users of electrical equipment. It was believed that additional information might lead to a better understanding of dielectric break-down such as occurs on windings and aid in the development of maintenance testing procedures for older windings∗ Previous test work had been on older windings with various types of tests. The results were inconclusive particularly because a few very large samples were tested. This paper represents a comprehensive testing program wherein several types of mica insulations were subjected to various a-c and d-c tests. Large numbers of samples were tested to permit statistical analysis of the data.