A Hybrid Thermal Modeling Method for Traction Motors Used in Duty-Cycles

This paper presents an approach to calculate temperature in the electrical machines critical parts when operating in intermittent operations. Focus in this paper is particularly placed on the traction motors that should be run in duty cycles with thousands of operating points during several hours, e.g. in e-mobility and railway applications. Normally, application of numerical methods in duty-cycle calculations is limited due to the long computation time which, in turn, results in a lower accuracy in temperature estimation. Here, numerical models are simplified and used efficiently together with analytical models so that calculation time is reduced significantly. The numerical methods include computational fluid dynamics and finite element models. The reduction in calculation time is from hours to minutes. The developed numerical and analytical methods are verified by measurements on an open self-ventilated traction motor and a good agreement is achieved both in transient and at steady-state temperatures.