Conceptual design of sleeve rotor synchronous reluctance motor for traction applications

Synchronous reluctance machines are very appealing for high speed traction motor design due to their robustness, simple structure, absence of magnets, and simple control. The absence of magnets means that synchronous reluctance machines are not susceptible to price variability and sustainability of rare-earth materials. Also, there are no concerns about demagnetization or uncontrolled generation mode. However, the challenge of achieving a good constant power to speed ratio is dependent on the mechanical aspects of the design. Conventional synchronous reluctance designs perform poorly compared to the permanent magnet machines due the presence of bridges and/or center posts in absence of the magnets to help saturate these regions. In this case, the challenge of rotor mechanical retention is addressed with the help of a sleeve on the rotor to reduce the need for bridges and/or center posts. Design optimization including the mechanical aspects of the sleeve is presented in this paper. The final design with a sleeve will be shown to be superior to a conventional design in terms of power density, rotor losses, saliency and torque ripple.