Novel In-Core Cooling of Yokeless and Segmented Armature (YASA) Axial Flux Machines

This paper presents a novel in-core cooling method for yokeless and segmented armature (YASA) axial flux machines to address the challenges posed by high temperatures in these motors, thereby unlocking their full potential. The in-core cooling method involves forming cooling channels within each stator core segment, through which a coolant is circulated to transfer heat from windings and core to the coolant. This solution increases thermal performance and reliability by effectively cooling the stator core and windings. Additively manufactured connectors are utilized to achieve integrity of cooling channels through adjacent segments. As a case study, the 36-kW YASA motor is analyzed using CFD and lumped parameter thermal network models. The results showed that the proposed in-core cooling can boost the current density to 18 Arms/mm² at the stator windings.