Robustness of a flux-intensifying permanent magnet-assisted synchronous reluctance machine focusing on shifted surface-inset ferrite magnets

Abstract

Flux-intensifying permanent magnet-assisted synchronous reluctance machines use relatively small amounts of non-rare earth permanent magnets, making them viable alternatives for remanufacturing older machines, aligning with EU directives and circular economy principles. The asymmetric rotor topology is particularly suited for micromobility applications, which benefit from shifting inset magnets, as reverse motoring is rarely required. However, this design could be more sensitive to manufacturing and positioning errors of the magnets. To investigate the effects of the uncertainties of the shifted surface inset magnets, first, an optimal topology is selected based on average torque, torque ripple, and cogging torque using the NSGA-II optimisation method. The effects of the magnet shifting and its robustness are analysed using the Taguchi and ANOVA methods, validated by Full Factorial calculations. Results indicate a 31.25 % reduction in permanent magnet volume without compromising torque output with magnet shifting. The machine’s average and cogging torque remain within a 5 % robustness threshold for a $\pm$0.06 mm discrete manufacturing tolerance. Torque ripple may exceed this limit up to 14.77 %. However, the likelihood of exceeding the threshold is only 12.10 %. The reduced magnet volume and maintained performance make this topology a promising option for remanufactured machines in micromobility applications, supporting circular economy goals.