A High Strength Rotor Structure for IPMSM with Narrow Bridges

This paper proposes an asymmetric IPMSM structure that reduces magnetic flux leakage by applying easily manufacturable narrow bridges. Based on a theoretical approach to reduce the stress calculation time at the early design stage, inclined bridges and core edges are applied to reduce the stress of the bridges. The derived equations function as a guideline to design mechanically strong bridges, even when the shape of each pole is different. Stress analysis by FEM demonstrates the validity of the theoretical formula. Finally, the electrical characteristics of a conventional machine and our developed one, both of which had the same mechanical strength, are compared. The comparison clarifies that the no-load induced back EMF of our developed machine increases by 40%, and its copper loss under rated conditions decreased by 24% due to reduction of the magnetic flux leakage.