Design Considerations of a New IPM Rotor with Efficient Utilization of PMs Enabled by Additive Manufacturing

This paper presents a new design concept for interior permanent magnet (IPM) rotor using the capabilities of additive manufacturing (AM). In conventional laminated IPM topology, the presence of rotor ribs is essential for maintaining the mechanical integrity of the rotor. However, these pole ribs are a primary contributor to flux leakage, leading to inefficient utilization of costly rare-earth PMs. Addressing this challenge, a rib-less IPM rotor is proposed that takes advantage of the AM potential which eliminates the need for traditional ribs while maintaining the structural integrity of the rotor. Nevertheless, the additively manufactured cores, in contrast to conventionally laminated rotor cores, demand specific design considerations, especially in terms of eddy current loss and structural performance. In this regard, a strategy involving the incorporation of shallow grooves on the rotor surface is employed to mitigate eddy current loss. The mechanical performance of the proposed topology is carefully examined, and the impact of pole geometry on rotor displacement induced by centrifugal forces is investigated. To evaluate the performance of the proposed topology, an optimization procedure based on response surface methodology is conducted for both the proposed rotor and a conventional IPM rotor. The results indicate that the proposed IPM topology can offer significantly more efficient utilization of PMs and enhanced torque rating by approximately 8% compared to the laminated IPM topology.