Fan Performance Analysis for Rotor Cooling of Axial Flux Permanent Magnet Machines

The thermal management of an axial flux permanent magnet (AFPM) machine is essential because it determines the machine's continuous power output and reliability. In this paper, a secondary cooling method is proposed using rotor cooling, which allows better thermal management on the permanent magnets that are attached to the rotor. This will reduce the potential of the machine failing due to magnet demagnetization and degradation. Thermal analysis via lumped parameter networks is usually sufficient in predicting the motor's thermal behavior. However, the accuracy of the prediction can be increased, especially for the devices with complex flow regions by computational fluid dynamics. In this study, the fan blade was attached to the rotor of a yokeless and segmented armature machine for flow validation and then three different fan blade designs from other engineering applications were tested. The evaluation includes the flow characteristic, power requirement, and thermal characteristic for the AFPM's rotor cooling applications. Additionally, the rotor cooling performance index is introduced to assess each fan design performance.