Design of the Water-Cooling System for the Stator Assembly of YASA Motors

With the increasing demand for high-efficiency and high-power-density motors in new energy vehicles, aerospace and other fields, axial flux permanent magnet machines (AFPMMs), especially yokeless and segmented armature (YASA) axial flux motors, have become research hotspots due to their compact structure and high power density. However, the special structure of YASA motors leads to harsh heat dissipation conditions at winding ends and strong coupling between electromagnetic characteristics and temperature fields, making thermal management crucial. This study focuses on enhancing the heat transfer design of the water-cooled bracket for the stator assembly of YASA motors, as the bracket serves as a key heat transfer medium between the stator core, windings, and cooling system. Taking the traditional stator bracket (with cooling water jackets only arranged on the stator inner wall and support fins as the main heat transfer structure) as the baseline model, three cooling enhancement schemes are proposed: Model 1 replaces bracket fins with heat pipes in indirect contact with cooling water; Model 2 optimizes Model 1 by extending heat pipes directly into the water channel for direct contact cooling; Model 3 integrates independent cooling liquid pipes inside fins connected to the main cooling pipeline. Temperature rise tests under the same current input conditions were conducted. Results show that Model 3 achieves the best temperature control performance, with maximum temperatures of 64°C, 67.4°C, and 75.4°C under the three operating conditions—36.7%, 49.3%, and 52.5% lower than the baseline model, and 29.9%, 33.8%, and 38.6% lower than Model 1.Model 2 balances cooling performance and loss, maintaining low loss levels in all conditions. This study provides experimental basis for optimizing YASA motor cooling designs.