Stator Slot Design Guidelines for Concentrated Windings with Direct Liquid Cooling Channels for Electrified Aviation

High power and torque densities are essential to achieve weight reduction in electric propulsion systems. For the future integration of highly utilised electric machines into aircraft propulsion, these must be evaluated also with a focus on service life and reliability. Typically, the components that limit the lifetime of electric machines are the bearings and the insulation of the stator winding. In addition, high power densities and efficiencies are essential for the realisation of electrified aviation. One method to achieve high power densities is to increase the current density. Direct liquid cooling can regulate the resulting temperature within the slot, thus managing thermal aging and increasing insulation reliability. This paper develops stator slot design guidelines for concentrated hollow conductor windings for direct liquid cooling to achieve higher power densities, highlighting the importance of current displacement and temperature-dependent resistance.