Complete Analysis of Motor Temperature Rise

The present-day demand and imperative need for higher speeds and increased outputs in every phase of industry and transportation have emphasized the tremendous importance of realizing the maximum utilization of the service capacities built into electrically-driven equipments. In a great majority of cases the predominant limitation in this direction lies in the heating capacity of the electric motors and this paper has been written to show a general method of ``mapping´´ the heating performance of electric motors over their entire speed-torque operating range so that their maximum performance may be judiciously realized within their heating limitations. Many excellent papers have described methods by which, starting from design constants and losses, the temperature rise of a machine can be calculated for a given load condition. Also some of the earlier papers¹ have brought out the fundamentally simple functions which govern the temperature rise of electrical machinery. In this paper, the authors show how, starting from the results of a small number of tests, it is possible to build up a complete temperature rise map of the motor applicable to any conceivable speed and torque service condition. This method was worked out in detail for the single-phase, commutator-type, traction motors which equip the modern a-c locomotives and the enlightened interest of the Pennsylvania Railroad led to the preparation by two electrical manufacturers of an unusually complete analysis of traction motor performance.