Design and Optimization of a Novel External-Rotor Axial Flux Motor for In-Wheel Application

This paper proposed a new external-rotor yokeless and segmented armature axial flux machine applied in-wheel traction. The loss analysis for the motor cooling casing is performed based on finite-element method, and the height of the cooling fins is optimized to decrease the eddy current loss and increase the efficiency of the motor. Subsequently, epoxy potting is developed to increase the heat transfer efficiency. On this basis, thermal analysis is conducted to verify the temperature of the stator. Finally, the in-wheel motor is manufactured and tested, and the measured data matches well with the results of the electromagnetic and thermal analysis. Compared with the radial flux PM (RFM) motor in the same volume, the peak torque and peak power of the YASA are 1.67 times and 1.3 times of the RFM respectively.