A novel grain oriented lamination rotor core assembly for a synchronous reluctance traction motor with reduced torque ripple

High torque density and low torque ripple are crucial for traction applications. These allow the electrified powertrains to perform properly during start-up, acceleration, and cruising. Achieving these goals requires improvement to the saliency of the rotor geometry which means higher magnetization in the flux carriers and lower magnetization through the flux barriers. Recent advantages of high quality anisotropic magnetic materials such as cold rolled grain oriented electrical steels is a potential for achieving energy efficient, compact, and high performance synchronous reluctance machines. However, the cylindrical geometry of the rotor is an obstacle to utilizing these materials for rotor lamination with number of poles higher than two. This paper presents an innovative rotor lamination design and assembly using cold rolled grain oriented electrical steel along with a new analytical approach for rotor flux barrier design for achieving a higher torque density and lower torque ripple for a 4-pole synchronous reluctance motor. The design methods and prototyping process are discussed, finite element analyses and experimental examinations are carried out and the results are compared to verify and validate the proposed methods.