Rotor design and optimization of synchronous reluctance machine with low torque ripple

The rotor structure of a synchronous reluctance machine (SynRM) affects the variation of reluctance and has an important effect on the torque performance of the machine. To improve the torque performance of SynRM, the optimization design of the rotor structure is essential. In this paper, a multi-objective snake optimizer (MOSO) is proposed by combining snake optimizer with multi-objective optimization strategies. Integrated with finite element analysis and the MOSO optimization method, the SynRM with a fluid-shaped rotor structure is optimized to improve torque performance. Compared with several algorithms, such as multi-objective genetic algorithm, multi-objective particle swarm optimizer, etc., the MOSO optimization method achieves better results in optimizing the fluid-shaped rotor structure with higher torque and lower torque ripple of the machines on its Pareto frontier, which verifies the superiority of the proposed MOSO optimization method. In addition, a Bezier-shaped flux barrier tip determined by curve fitting with arbitrariness is proposed to reduce the torque ripple of SynRM further. Different machines on the Pareto front of the MOSO optimization method are selected to optimize the shape of the flux barrier tip. The percentages of reduction in torque ripple for the SynRMs that have been designed with Bezier-shaped flux barrier tips are 27.27%, 47.21%, 69.71%, and 78.71%, respectively. The decrease of torque ripple for the several SynRMs verifies the effectiveness of the Bezier-shaped flux barrier tip.