Investigation of hot-spot temperatures in fractional-horsepower motors

THE revision of American Standard C50, “Rotating Electrical Machinery,” resulted in various suggestions for changing the method of measuring the temperature rise of motors and for establishing temperature-rise limits to be used with these methods. A review of the temperature tests taken in the past indicated that they are of little value for comparing the various methods. Few tests included temperature measurements by more than one method, and none of them had enough embedded detectors to measure accurately the hot-spot temperature. In order to obtain accurate data the authors were asked to make temperature tests on fractional-horsepower motors and to report the results. It was believed that the data thus obtained would be valuable to the standardizing committees of the AIEE, the American Standards Association, and the National Electrical Manufacturers Association, as well as to motor users.