Driving Cycle Simulation of Wound-Rotor Synchronous Machine with Hairpin Windings Considering AC-Losses

Hairpin windings are a promising option to manufacture armature windings of electric machines while assuring the manufacturing process' repeatability and scalability often demanded by the automotive industry. This type of winding presents the advantages of a high slot fill factor, leading to a low DC-resistance and a high thermal conductivity inside the slots when compared to wound windings. However, hairpin windings are currently limited in the number of conductors per slot due to the manufacturing effort. Thus, this type of winding relies on conductors with a high cross-sectional area, which might lead to an increase of eddy-current losses at higher speeds. In automotive applications, the operating point of an electric traction machine may vary considerably. Hence, it is important to assess the machine performance for a complete range of operating points. This work uses driving cycle simulations as means of obtaining representative operating points for the traction machine. During the driving cycle, the machine's performance characteristics are taken from pre-calculated performance maps. A salient-pole, wound-rotor synchronous machine is chosen as an exemplary traction machine in the analyses. This work evaluates the total energy demand of a traction machine for different driving cycles and quantifies the additional energy dissipated at the armature winding due to eddy-current effects. Since the batteries' size is one of the most cost-relevant components of a full-electric vehicle, the additional energy dissipated is a key performance indicator of hairpin windings for the automotive sector.