Prototyping experiences on 48V starter-alternators

This paper reports the design experience faced during the prototyping and testing stages of two multiphase induction starter-generators for 48 V mild-hybrid powertrains. The focus of the investigation is on the pole numbers and their influence on the electrical machine parameters and performance. According to the application and the usage profile in a real urban drive cycle, a 8 pole prototype has been initially designed. Since the designed magnetic circuit was also suitable for a 6 pole configuration, a second prototype with this pole count has been produced. In fact, the pole number reduction could lead incremental advantages with respect to efficiency and power factor as a result of the lower fundamental supply frequencies. The performance comparison in terms of torque, efficiency and power factor of the two prototypes have been investigated and validated both by means of simulations and experimental activities.