Cylindrical Wound-Rotor Synchronous Machines for Traction Applications

Among the synchronous electrical machines without permanent magnets, the wound-rotor salient pole solution has been recently used by some major carmakers for traction applications. However, in salient pole rotor structures the field conductors are subjected to large centrifugal forces when the machine operates at high rotational speed, in particular when unpotted winding are adopted. For this reason, the paper investigates the possibility of using cylindrical woundrotor structures as a viable solution for automotive traction applications. Assuming an existing salient pole prototype as baseline, a cylindrical rotor has been sized to fit in the same stator bore. On the basis of analytical and finite element analyses, the paper initially compares the two rotor structures from the electromagnetic point of view. In addition, the paper includes the preliminary verifications of the mechanical robustness for the sized cylindrical rotor design.