Progress in the thermal design of oil-cooled rotating electric machines

IN THE PAST electrical designers have been hindered by the fact that internal temperatures in a machine were not known with sufficient accuracy. At best they had to be content with average temperatures estimated from measured coil resistances, for example, but the actual location of hot spots and the temperature distribution in the machine components have been difficult to establish. With the increased availability of high-speed digital computers, it is now possible to determine these temperatures. The purpose of this paper is to illustrate how temperatures can be determined in components of electric machines by an iteration technique that has been successfully programmed for the IBM (International Business Machines Corporation) 650 digital computer.