How is the temperature class for magnet wire insulation determined?
Samples of insulated wire are made into twisted pairs and aged at a series of temperatures significantly higher than the expected temperature class rating of the insulation. The twisted pairs are periodically proof tested at 300 to 1200 volts depending on the wire diameter. Sample failures are recorded and an average life at each temperature is calculated in accordance with procedures established in ASTM D2307. From these values a regression line is calculated to determine the temperature at 20,000 hours of aging. This temperature must be equal to or greater than the proposed temperature class for the insulation.
