Design and Testing of a Carbon-Fiber-Wrapped Synchronous Reluctance Traction Motor

Synchronous reluctance machines are very appealing for high-speed traction applications 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 permanent magnet machines due to the presence of bridges and/or center posts that provide a path for performance-robbing leakage flux and the absence of permanent magnets that help saturate the bridges and/or center posts. Elimination or reduction of these features presents a challenge for rotor mechanical retention due to the reduction in radial stiffness that these members provide mainly for high-speed applications. A carbon-fiber sleeve on the rotor will provide the needed mechanical strength to enable a reduction of bridges and/or center posts. This paper will present the design details, analysis, manufacturing, and test results of a proof-of-concept carbon-fiber-wrapped synchronous reluctance machine targeting traction applications.