This paper proposes a sustainable magnet thermal class selection methodology for permanent-magnet (PM) traction motors. Irreversible demagnetization (ID) occurs when thermal and armature-reaction stresses push the magnet operating point below the B–H curve's knee. The traditional safeguard of specifying magnet grades rich in heavy rare-earth elements dysprosium (Dy) or terbium (Tb) leads to increased costs and severe environmental impact. The proposed workflow integrates temperature-dependent B–H characterization, two-way electromagnetic-thermal analysis, and worst-case negative d-axis current synthesis. A case study of a 10-pole, 140 kW traction motor is presented for exemplification. Through this approach, the lowest PM grade is successfully identified, providing desired ID withstanding ability under the US06 driving cycle, short-circuit faults, and cooling system degradation. This automated workflow accelerates eco-efficient motor design, safeguarding torque and efficiency without costly overspecification, and offers a scalable path to greener electric drives.

Rare earth magnets have long been the cornerstone of high-performance electrical machines owing to their exceptional magnetic properties. However, their utilization presents challenges, notably in terms of cost and limited availability of resources. In response, ferrite magnets have emerged as a promising alternative due to their cost-effectiveness and abundant supply. Vernier permanent-magnet (VPM) machines typically exhibit low power factors due to high winding reactance. Given the weaker magnetic properties of ferrite magnets compared to rare earth counterparts, ferrite-based machines inherently suffer from poorer power factors. Short pitch winding is a known strategy to mitigate this issue and enhance power factor. This paper investigates the impact of employing short pitch winding in ferrite VPM machines, alongside an exploration of different gear ratios. The research findings indicate that when a high-power factor is desired, employing short pitch winding can lead to higher torque/power and efficiency compared to full pitch winding in ferrite VPM machines. Moreover, the advantages of short pitch winding are more prominent with higher gear ratios. Finite element analysis is employed to optimize both the machine's topology and performance, providing insights into the intricate interplay between winding configurations, gear ratios, and magnetic materials.

In this paper, the influence of full-pitch and shortpitch windings on the torque and power factor of permanentmagnet vernier (PMV) machines is studied.It is well known that the short-pitch (SP) winding has shorter end windings but with a lower winding factor.Thus, to achieve the largest torque, the full-pitch (FP) winding is preferred in PMV machines.However, it is found in this study that the SP winding, rather than the FP winding, is a better choice to achieve higher output torque of PMV machine at a high power factor level under the same PM consumption.The advantages of SP winding are even more obvious at higher electric loading and higher power factor levels.The theoretical analysis indicates that both torque and power factors are influenced by the winding factor, providing the possibility of better performance of the SP winding than the FP winding.This is further confirmed by the optimization results after performing the multi-objective optimization considering torque, power factor, and PM consumption.Finally, a prototype is manufactured and tested to validate the analysis.

This paper presents a high power-factor permanent magnet vernier machine (PMVM) employing hybrid concentrated-winding (CW). The hybrid winding, carrying both delta- and star-winding sets, allows for low harmonic tooth-wound coil and satisfied winding factor for PMVM with high gear ratio. Therefore, the torque density of the PMVM can be enhanced with reduced end-winding length and more compact structure. More importantly, the mutual inductances between the three phases and the coils that comprise each phase are reduced to a large extent in the hybrid winding, without deteriorating the output torque capability. As a result, the presented PMVM possesses a lower ratio of inductance to PM flux linkage due to the low-harmonic and low-coupling winding, and hence, improved power factor. Two benchmark PMVMs with identical gear ratio have been optimized for comparison. Further finite element results verify that the proposed CW PMVM presents superior performance in terms of end-winding length, torque density, power factor, and efficiency. It is revealed the proposed hybrid CW PMVM can improve the torque density to 23Nm/L from 21Nm/L and 14Nm/L, with the consideration of end-winding volume, and power factor to 0.86 from 0.72.

This paper investigates the two-slot pitch winding vernier machine by stator shifting technique (SST). It shows that the conventional two-slot pitch winding vernier machine can be generated by SST with a special stator shift angle. This paper contributes to exploring other shift angles and their influences on machine performances. Analysis results indicate that different shift angles have a great effect on the armature winding magnetomotive force (MMF) harmonic contents and the flux modulation effect. Consequently, the phase inductance, power factor, core losses, and torque capability will be affected. A single-layer 24-slot/10-pole vernier machine is investigated for verification, and the results show that with an appropriate shift angle, the power factor is improved from 0.6 to 0.7, the iron losses are reduced by 24.5%, and the efficiency is improved by 0.7%, with a slight torque drop of 2.9%.