Hollow direct air cooled windings: Rotor design process

This paper presents theoretical and practical analyses of four different design options for an electrically excited synchronous machine (EESM) with hollow field winding conductors for internal air cooling. This cooling concept allows for effective direct cooling of the windings.Simulations are performed for the electromagnetic evaluation of the proposed designs, while a plastic 3D printed rotor mock- up is used to validate the winding method. The electromagnetic simulation results are used to estimate the increased losses during nominal excitation, for a comparison with a hypothetical corresponding PMSM. The rotor mock-up proved to be an effective way to test winding methods and rule out design options that worked well in theory, but not in practice.Based on the theoretical and practical analyses, a conclusion is drawn on what rotor design option is most suitable for this direct cooling concept. The chosen design has separate rotor teeth assembled to the rotor yoke with dovetails.