Nine-Phase-based Fractional-Slot Winding Layouts for Integrated EV On-board Battery Chargers

Permanent magnet (PM) machines configured with fractional slot concentrated winding (FSCW) have recently been employed in electric vehicle (EV) powertrains thanks to their myriad merits over conventional designs. The concept of integrated on-board battery chargers (OBCs), where the propulsion components are employed in the battery charging process, has also shown promise to provide a cost-effective alternative to conventional on-board and/or off-board chargers. This technology highly depends on the machine type as well as the employed winding design. Most of the up-to-date research covering this topic has mainly focused on multiphase machines with conventional distributed winding owing to their high-quality flux distribution. Despite the outstanding features of FSCW, their inevitable flux distortion constitutes the main drawback of this winding layout. This paper evaluates the performance of two nine-phase-based integrated OBCs using surface-mount permanent magnet (SPM) synchronous machines equipped with two different fractional-slot layouts, namely, the non-overlapped FSCW 18-slot/16-pole and overlapped fractional-slot winding 18-slot/10-pole with two-slot coil pitch. The design optimization of the two machines has been obtained based on analytical magnetic equivalent circuit (MEC) models. While, finite element simulation has been used to evaluate the two designs under both charging and propulsion operational modes.