Permanent Magnet Assisted Synchronous Reluctance Machine Design for Light Traction Applications

This paper presents a systematic comparative design study of permanent magnet assisted synchronous reluctance (PMaSyR) machines for a light traction application aimed at considering an holistic approach for a given outer envelope and cooling system specification. Electromagnetic, structural and thermal aspects are all accurately considered in a computationally efficient manner using a hybrid analytical-finite element (FE) design approach. The SyR machine geometries providing the maximum torque with increasing number of poles are identified and their performance deeply investigated with full FE analysis. The study has been carried out considering several requirements in terms of base and maximum speeds with the aim of drawing general design considerations. Results reveal that the optimal pole number from a torque perspective depends on the considered maximum speed. The reasons behind this behavior are fully investigated as well as how and why the optimal geometries change. The optimal SyR machines are then compared also considering the insertion of permanent magnets within the rotor slots with the aim of maximizing the constant power speed range. The rationales behind the selection of the machine to manufacture are then outlined including aspects related to efficiency and demagnetization under the worst short circuit condition in the entire torque-speed range. The optimized machine (after a FE-based design refinement) has been manufactured and tested on an instrumented test bench validating the proposed design approach and the deduced design insights.