This thesis introduces the results of the study about the thermal modeling conducted through the collaboration between Politecnico di Torino and ABB AB. The Aim of the project is to become a reference for the definition of an innovative thermal model relative to an asynchronous motor for railway traction. Calculations are done in Ansys and are then compared with the results obtained in the ABB laboratories. The thesis can be divided in four main topics. The first chapter is concentrated on different cooling layouts for electric motor, operating conditions of traction motors and different thermal modelling methods. The second chapter deals with all the challenges that a thermal analysis and the design of a thermal model can bring about motors in the railway field.