The application of class B insulation to auxiliary-type D-C motors in severe duty service

P. L. Alger (General Electric Company, Schenectady, N. Y.) and R. E. Hellmund (Westinghouse Electric and Manufacturing Company, East Pittsburgh, Pa.): An important feature of this paper is the information given on the relative values of winding temperature-rise by the resistance and by the thermometer methods. Figure 5 indicates that, due to the time lag of the thermometer temperature, the ratio of the armature rise by thermometer to rise by resistance is only 0.60 for a half-hour test and 0.67 for one hour, as compared with 0.87 under a continuous load. These ratios are for a totally enclosed motor, and even lower ratios apply to open or forced-ventilated d-c machines.