Calculation of the Maximum Mechanical Stress on the Rotor of Interior Permanent-Magnet Synchronous Motors

This paper proposes a novel analytical method to calculate the maximum mechanical stress (MMS) on the rotor of the interior permanent-magnet synchronous motor with V-shaped rotor structure. Based on the traditional equivalent ring method, an improved method, which draws on the principle of equivalent centroid, is proposed to calculate the mechanical stress on the bilateral magnetic bridge. A rotor model with spokes is also built to calculate the mechanical stress on the central magnetic bridge. The stress concentration factor, together with its selection method, is also defined to calculate the MMS on the junctions. Then, the changing trends of the mechanical stress on the bilateral and central bridges are obtained along with the change in the V-shaped angle. The rotor faults of the two IPMSMs are analyzed based on the research results, and the optimized prototype is designed and fabricated. Experimental results of the optimized prototype show that the proposed equivalent methods have great applicability. Finally, the suggestion to design the V-shaped rotor structure is presented to determine the design rapidly and accurately.