High Power Density Axial-Flux Permanent Magnet Motor for Electric Bike Application

The demand for electric bikes has been increasing in recent years, and so has their drive, which requires a high power-to-weight ratio or a high power density. An axial-flux permanent magnet motor with a Halbach-array is an excellent choice for electric bike drives thanks to its known characteristics of high power density, reliability, and efficiency. However, because an axial-flux machine topology is not common, the manufacturing process can be challenging, especially in the stator core. A good solution to this problem is to remove the stator tooth tips, as this simplifies the stator core shape and makes manufacturing easier. The proposed electric bike has limited housing dimension constraints; thus magnet sensors were implemented to support the Hall sensors in detecting the rotor position. The designed models were analyzed using the 3D finite element method (FEM) to determine their electromagnetic and thermal characteristics. A prototype was manufactured based on the final design and tested under rated conditions to validate the analysis results.