Conjugate heat transfer analysis of a salient pole rotor in an air cooled synchronous generator

Abstract

A study of combined heat transfer by conduction and convection for the rotor of an air-cooled, 4-pole generator was carried out using a general purpose CFD code. A simplified generator design was used to demonstrate a technique to analyse temperature distribution through the salient pole rotor at the design stage. Whilst CFD has the capability to predict airflow and convective heat transfer, it is shown that it is also necessary to model heat conduction, including the heat input from the losses, to produce a realistic thermal model of the rotor. A strip-on-edge coil structure is considered and it is shown that modelling the coils as homogeneous materials with anisotropic thermal conductivity provides sufficient accuracy for the prediction of local coil temperatures. Consideration is given to the effect of the coil size and structure on the cooling. To demonstrate the capability of the method, a modification to the test model considered is presented in which the airflow is modified, leading to enhanced heat convection and field coil temperature reduction.