In this article, the authors present the various choices made to design a magnet free and directly recyclable pure synchro-reluctant (Pure-SynRel) machine with asymmetrical poles operating at a maximum speed of ~21,000 rpm dedicated to automotive.
This project focused on identifying design levers and optimizing the magnetic circuit to address three well-known challenges of this topology that limit its application as an automotive traction machine. These challenges include: maximizing the power factor to reduce inverter rating and cost, minimizing sources of NVH (noise, vibration, and harshness) and torque ripples, and ultimately maximizing efficiency to bridge the performance gap with magnet-based technologies (PMaSynRel). The sizing of stator components—such as the choice of winding (concentric or distributed, full or fractional pitch, round or hairpin wire)—and rotor components (e.g., the number of pole pairs, shape, and number of barriers) are explained. Additionally, the optimization methods and mechanical solutions employed to achieve maximum speed are detailed.
A machine with symmetrical poles was firstly designed, with torque ripples of 24% which is over the automotive acceptation levels. Based on this version, an adjacent asymmetrical pole was created, reducing the torque ripple by 56% and limiting the torque drop to 6%. After optimization, the proposed machine generates a maximum torque of 172 N.m and 220 kW of maximum power. The torque ripple and power factor at maximum power are 14% and 0.64 respectively. A prototype is currently being built and will be tested on a test bench at IFPEN. The theoretical expectations will be verified and presented in a future paper.