Design Optimization of Four-Layer Fraction Slot Concentrated Winding Spoke-Type Interior Permanent Magnetic Machine for Range Extender

In this article, the design optimization of a four-layer fractional slot concentrated winding (FSCW) interior permanent magnet (IPM) machine for range extender is proposed for high energy efficiency and excellent torque/back-electromotive force (EMF) performance. The design starts with the comparison of four-layer FSCW patterns in terms of efficiency distribution based on a predesign spoke-type rotor model. Magnet segments and rotor auxiliary notches (ANs) are applied and optimized to reduce eddy current losses and torque ripples in the permanent magnets (PMs). Then, an efficient two-step optimization of multiple performances for a machine is presented. The rotor parameters are designed by an analytical model with a Pareto optimizer for torque capacity and ripple. An interpolation-based design method for adaptive stator slot parameters and winding configurations is presented to quickly obtain the optimal stator slot winding designs corresponding to the rotor design to achieve optimal efficiency. The multi-bridge design is applied to rotor laminations to suppress flux leakage, making the rotor core easy to manufacture. Finally, an 18s-16p four-layer FSCW prototype was built and tested to verify the design optimization results, with a maximum efficiency of 96% and rated shaft ripple as low as 3%.