Investigating the air flow rate of self-ventilated traction motors by means of Computational Fluid Dynamics

A self-ventilated traction motor was investigated by means of Computational Fluid Dynamics (CFD) with special emphasis on the prediction of its cooling air flow rate. This investigation was suggested by the fact that the motor had to be designed in a non usual way as far as air flow is concerned and the subsequent thermal design of the motor had to be based on a well predicted flow rate. The cooling flow through the investigated motor is driven by an axis-mounted radial-blade centrifugal fan. Two variants of the motor differing in its fan wheel were analyzed by means of CFD. One of the two fan variants employs a two-fans-in-one-wheel configuration. The results together with analytical fluid-mechanical considerations helped to judge between these variants under the premise of maximum flow rate.

I. Introduction

The thermal management of traction motors is of crucial importance in order to reach high power-volume densities (see for instance [1]). For the thermal calculation procedure to be efficient it is necessary to have on the one hand calculation networks which represent the thermal capacities of the machine as well as the path along which heat is being transferred. Especially in the case of traction motors simulating the heat flow in the time domain is mandatory as the motor design must be based on prescribed operational cycles [2].