The rise and distribution of temperature in small electrical machines

The paper deals with the factors influencing the shape of the heating and cooling curves of coils and electrical machines. The thermal conductivity of the insulation is calculated by alternative methods from the distribution of temperature in coils: and the effects of different temperature-rises and of different air velocities upon the thermal conductivity and upon the temperature-rise per watt are considered. A new arrangement for measuring the mean temperature-rise of field windings is described. The temperature-rise of the field windings is deduced in terms involving the speed and the armature loss for a number of different machines, and a comparison is made of the temperature-rise as measured by resistance with that measured by thermometer.