Thermal Analysis of Large Hydro-Generator Based on a Multi-physic Approach

摘要

The thermal analysis of the main components of hydrogenerators, namely the stator, the rotor and the cooling system, is a complex issue that deals with several physical phenomena. The first to be addressed is the electromagnetic field which produces a significant portion of the losses. Secondly, the science of fluid mechanics is needed to evaluate the heat transfer between the cooling air and the solid parts of the generator as well as the windage losses and their distribution. Last but not least, is the phenomenon of heat transfer by conduction taking place through the various isotropic and anisotropic components of the generator. Ideally, a fully coupled multi-physics model should be used which would imply solving Maxwell's and Navier-Stokes equations coupled with the energy equation. As this is still computationally too demanding, the project presented herein has started with a more simple approach of simulating each aspect separately and exchanging results of one field with the other as a weak coupling. With this approach, the thermal analysis can readily include results from electromagnetic and computational fluid dynamics (CFD) simulations to evaluate the temperature field, and consequently the hot spot temperature and its location. This is done by solving the Fourier partial differential equation using Finite element/Finite volume methods. In parallel with simulations, on-site measurements of the various losses on existing generators at different loads and the measurement of several critical temperatures provide the data to calibrate and validate the models. This paper explains the step by step process and presents some computational and experimental results on an existing 122.6 MVA hydrogenerator at Hydro-Quebec.