Hollow Direct Air Cooled Rotor Windings: Experimental Verification

This paper presents the experimental verification of a cooling concept based on hollow direct air cooling windings for the rotor of an electrically excited synchronous machine (EESM) with the application of traction drive for electric vehicles (EVs). Developing the performance of EESMs is important for the EV industry since it is today so reliant on permanent magnets. The idea behind the cooling concept is explained and the prototype machine made for the experimental verification presented. The results of the experimental work show that the direct air cooled hollow windings can maintain a continuous current corresponding to a copper current density of 21.1 A/mm² or a rotor slot current density of 8.5 A/mm².