Longitudinal and Transverse Heat Flow in Slot-Wound Armature Coils

Abstract

IT has long been recognized that the heat generated in embedded armature conductors by the I 2 R and eddy current losses in part escapes by transverse flow through the insulation from the copper to the iron (possibly, to a more limited extent, to the air at the ducts) and in part flows longitudinally along the copper to the ends of the coils exposed to the cooling air. The importance of a solution of the combined transverse and longitudinal heat flows has been realized, for upon these the internal copper temperatures must necessarily be dependent. Thus, it has long been known that in a machine of short core length, the iron temperature and temperature at the center of the machine by detector between coil sides could usually be reduced by increasing the volume of air blown upon the ends, but in machines of long lengths (say 50 inches or more), the temperature at the middle could not be so reduced. Again, it has been recognized that as a machine of a given diameter is lengthened, assuming a short core length (say 10 inches for the shortest) the temperatures increased, although the losses per inch of length remained nearly the same.