Some problems in the standardization of temperature ratings of fractional-horsepower motors

AT the winter convention of the AIEE in New York in January 1939, there, were presented a number of papers on temperature rating of electrical apparatus.^1–6 Since that time AIEE Standards No. 1 has been tentatively revised to favor the resistance method for determining the temperature rise and changing the limits for this method from 55 degrees to 60 degrees centigrade. Little data have been published on how the proposed changes in standardization might affect fractional-horsepower motors. For this reason the study out-lined in this paper was undertaken. It is hoped that the information given herein will be of some assistance in standardization problems affecting fractional-horsepower motors. It is further hoped that others who have similar data on fractional-horsepower motors will make them available, regardless of whether they may support or differ with the data in the paper, in order that correct information representative of the industry may be available to those who make the standards, or any future revision of them.