Transient Thermal Modeling and Analysis of Railway Traction Motors

This paper presents a practical approach to model and analyze transient thermal effects in air-cooled electric traction motors. The developed thermal modeling method enables accurate estimation of temperature in motor critical parts including winding and bearing. Advantages of both numerical and analytical modeling methods are exploited with the aim of realizing accurate estimation of hot spot temperatures in traction motors while keeping the computation time within a reasonable range. Computational fluid dynamics simulations are carried out to model air flow in the motor in order to provide heat transfer boundary inputs to the developed combined finite-element (FE) and lumped parameter (LP) thermal models. The combination of the FE and LP models keeps the size of the model relatively small and enables running transient calculations reasonably fast. Also, the developed model provides the possibility to study the influence of stator and rotor duct blockages on the motor thermal performance, which is a common root of failure in traction applications during operation in dirty environments. The proposed thermal model is verified using experimental results on a traction motor equipped with temperature sensors at different running conditions and a good agreement between the estimated and measured temperatures is achieved.

I. Introduction

In the competitive railway market, requirements for high-performance and low-cost solutions signify a demand for compact drives with a high torque/volume ratio. This means as well as design improvements with the aim of increasing compactness and efficiency, the traction motors should be run at their thermal and electromagnetic limits. The maximum possible utilization of motor arises the need for advanced electromagnetic and thermal design tools in order to enable accurate estimation of motor performance during service operation in a design phase. An overview of the literature and tool developments during the last years shows an unbalanced level of progress among electromagnetic and thermal tools.