Fatigue Life Calculation and Mitigation of Bridge Stresses in the Rotor Core of a Delta-Shape Interior Permanent Magnet Motor

Air flux barriers and bridges are critical rotor topology structures for better electromagnetic performance in permanent magnet machines. Rotor parts in these machines experience high and fluctuating stresses, which may lead to fatigue failure of these metal bridges. Further, the heat generated due to core losses results in thermal stresses, which append to the stresses due to centrifugal force. This paper presents a design strategy to evaluate the fatigue life of the rotor structure considering thermal and mechanical loads from a drive cycle. Moreover, the rotor topology is optimized to meet the stress limits without compromising the electromagnetic targets.