A New Navy Classification Criterion for Insulation Life

Meaningful thermal classification of insulating systems or magnet wires is based on the expected useful life at a given temperature. The Navy had established and used for more than a decade 40000 and 20000 hours as the minimum extrapolated test life at the rating temperature for varnish imaregnated and non-varnish impregnated insulation systems and magnet wires respectively. Following the setting of these standards, the Navy has continued to obtain and analyze aging data from new systems and wires with emphasis on the polyester types. The results of the continued research have led to a major modification in the Navy's classification criterion.