An analytical thermal model of an IC71W Induction Machine (IM) is presented, introducing the most relevant theoretical assumptions and equations. The validation of this model is conducted through experimental measurements. Some criteria for design of the most critical parts of the cooling system are provided using both a model based on Computational Fluid Dynamics (CFD) techniques and the analytical thermal model. First, the design of the water jacket and its main parameters are broadly analysed and some correlations for the design of the cooling ducts are presented. The influence of wafters on this cooling arrangement is also discussed.