Partitioned Stator Machines with NdFeB and Ferrite Magnets

Partitioned stator (PS) machines employ two separated stators to accommodate armature windings and permanent magnets (PMs), respectively, alleviating the space conflict in stator-PM machines, and hence boosting the torque density. However, the PM usage volume in PS machines is relatively large, and thus the material cost is high, which is undesirable for the cost-sensitive applications. In this paper, a PS machine employing ferrite PM is presented, which takes advantage of larger available space for PMs while balances the performance and cost. The electromagnetic characteristics of an optimized ferrite PS machine and an NdFeB PS machine are evaluated together with a classic Prius2010 interior PM (IPM) machine as a baseline. Meanwhile, the economic issues are considered. The results reveal that the NdFeB PS machine has higher torque density than the Prius2010 IPM machine, but is more expensive, while the ferrite PS machine can significantly reduce the cost and still exhibit good performance. The demagnetization behavior of the ferrite PS machine is evaluated and a new method to improve the demagnetization withstand capability is proposed. Moreover, the mechanical analysis is conducted for the cupped rotor of PS machines. Finally, a pair of small-scaled prototypes are manufactured to validate the predictions.