The Use of Computational Fluid Dynamics in the Thermal Design of Rotating Electrical Machines

Abstract

Thermal constraints impose limitations on the power capability of many electric motors and generators. However, inadequate data on ventilation air flows and convection heat transfer coefficients hamper the design process. Computational fluid dynamics (CFD) presents an opportunity to predict air flow and heat transfer in many situations. However, the complex geometries combined with rotation in the end regions of electric motors and generators present significant difficulties for CFD. An experimental study of air flow and heat transfer in the end region of a 200 kW 2 pole totally enclosed, fan cooled (TEFC) induction motor was carried out. Detailed measurements of heat transfer coefficient around the end windings and frame were made along with measurements of windage loss and airflow at particular locations within the end region. These were compared with a detailed model of the end region using the CFD software Fluent UNS and good agreement was found. The results are presented and the reasons for the difference between the measured values and CFD predictions are discussed. It is concluded that general purpose CFD software is now at a stage of development where it can be used in a design office environment to undertake design analysis of electrical machines.