A novel 24/30 external-rotor multi-tooth switched reluctance motor configuration for in-wheel electric two-wheeler propulsion

The electrification of two-wheelers is accelerating in India, where conventional internal combustion engine scooters remain major contributors to urban emissions. External-rotor (ER) motor configurations are widely preferred in electric two-wheelers due to their compatibility with in-wheel integration; however, limited rim space imposes stringent torque density requirements. Most current ER traction drives employ rare-earth permanent-magnet machines such as brushless DC (BLDC) and permanent-magnet synchronous motors (PMSMs). While permanent magnets contribute to high torque density and efficiency, concerns about supply-chain concentration, cost volatility, and environmental impact have intensified interest in magnet-free traction motor technologies. Switched reluctance motors (SRMs) are promising candidates because they eliminate the need for rare-earth magnets, offer a simple construction, high thermal robustness, inherent fault tolerance, and strong field-weakening capability. However, their typically lower torque density has limited deployment in commercial two-wheelers. To address this gap, this work proposes a novel 24/30 external-rotor multi-tooth SRM (ER-MTSRM) topology tailored explicitly for electric two-wheeler propulsion. The configuration delivers competitive torque performance while fitting within the same dimensional envelope as an existing ER-PMSM while retaining the magnet-free and structurally simple nature of SRMs. The electromagnetic behavior of the proposed machine is evaluated using static finite-element analysis (FEA). Further, the performance parameters of the proposed topology are refined through a driving-cycle-based multi-objective optimization. Maximizing average torque while minimizing electromagnetic losses and torque ripple constitutes the optimization objectives. Compared with the initial design, the optimized topology achieved a 7.11% increase in average torque, a 24.60% reduction in torque ripple, and a 5.78% reduction in weighted loss. The FEA framework employed is validated through experimental flux-linkage measurements on a downsized ER-MTSRM prototype, with an error of less than 4%, confirming the accuracy of the modeling approach. The results show that the 24/30 ER-MTSRM achieves PMSM-equivalent torque performance within in-wheel dimensional constraints.