Design and Comparative Analysis of IPMSM Topologies With Two-Slot Pitch Fractional Slot Overlapped Winding for E-Loader Applications

Permanent Magnet (PM) motors have been the obvious choice for light commercial vehicles such as electric three-wheeler cargo loaders, owing to their high torque and power density. Among these, interior permanent magnet motors (IPMSM) with fractional-slot concentrated windings (FSCW) have emerged as promising candidates for traction applications. However, a significant challenge with FSCW IPMSM lies in mitigating the sub-harmonic and super-harmonic components of the stator magnetomotive force, which can cause increased rotor losses and saturation effects. This paper investigates the optimal stator shift angle to derive the two-slot pitch fractional slot overlap winding (FSOW) for maximizing motor power output while maintaining the same motor dimensions and magnet volume— both of which are critical factors in electric vehicles as they directly have a bearing on the space utilization and cost, respectively. Subsequently, four different IPMSM topologies— flat, single V, delta, and double V employing optimized two-slot pitch FSOW are designed and analyzed comprehensively, using Finite Element Analysis (FEA). The design is based on the requirements of lightweight commercial 3-wheeler (3-W) cargo loaders (L5 Category). The topologies are then compared based on their electromagnetic performance, torque capability, and field weakening capability. Among all the designed topologies, delta emerges as the best candidate based on the performance metrics. Finally, an IPMSM with delta PM topology is manufactured and tested to validate the results from FEA as well as the conclusions drawn from the comparative analysis. The experimental results are also examined in relation to the operating points specified by worldwide harmonized light vehicles test procedure (WLTP).