Design and Analysis of the Cylindrical Hairpin Rotor Machine

This paper presents an innovative rotor design for electrically excited synchronous machines (EESMs), extending the advantages of hairpin windings from the stator to the rotor. The proposed machine employs a hairpin winding on the rotor, achieving superior electromagnetic performance through an increased copper fill factor compared to state-of-the-art EESMs. Particular focus is placed on the rotor design, addressing electromagnetic layout, winding arrangement, mechanical considerations, and manufacturing aspects. A 72-slot, 12-pole EESM featuring the hairpin rotor concept is analyzed using finite element analysis (FEA) and benchmarked against a conventional salient pole EESM in terms of torque and power density, back EMF characteristics, and efficiency.