Motorette tests: causes of variation in results

Four laboratories have tested motorettes specially prepared by a fifth, using a similar procedure to that recommended in AIEE 510 (IEEE 117). Heat aging was at 200°C and a 2.3: 1 difference in measured life was obtained between laboratories. Consideration of possible variations in procedure and testing have failed to establish any specific causes for the differences in the results, and it is concluded that the recommended procedure could not give an estimated maximum working temperature within better than 16 deg C.