Design refinements of synchronous reluctance motor utilising non-magnetic radial ribs for traction applications

The rotor structure of synchronous reluctance motor (SynRm) is usually provided with redial ribs to improve structural ruggedness for high-speed operation. While these radial ribs contribute to mechanical robustness, they also reduce the average torque and limit the flux-weakening capability due to an increase in inductance along the q-axis. To address this issue, the rotor design is refined by adopting non-magnetic radial ribs in this study. The introduction of titanium as non-magnetic material for radial ribs prevents magnetic leakage flux from flowing along the q-axis, and thereby improves the average torque, saliency ratio, efficiency and power factor of the SynRm. Furthermore, along with the electromagnetic analysis, the mechanical integrity of the proposed rotor design is also investigated. Two prototypes rated 1 kW at 1500 rpm are fabricated using both the conventional and the proposed rotor design, while the stator and other parameters are maintained constant in the two cases. The conventional design uses magnetic radial ribs whereas the proposed design uses non-magnetic radial ribs. Finally, a thorough comparative study, including inductance tests on the prototypes, is performed between the proposed and the conventional SynRm, confirming the strengths of the technology solution being set forth.