Integrated starter generator based HEVs: a comparison between low and high voltage systems

The purpose of this project has been to investigate the feasibility of 42 V mild hybrid electric versions of relatively large vehicles, like SUVs and light trucks. More specifically, this report focuses on the consequences on the integrated starter generator (ISG) performance brought by a reduction in voltage from the high (300 V) level of conventional hybrid electric vehicles to the new proposed standard (42 V). The discussion on ISG performance is substantiated by experimental tests conducted on two ISG prototypes, wired for 42 V operation, and the comparison with data from a 300 V version of the same machine. Inverter, battery and wiring limitations are discussed to give the specific motor performance broader significance. Safety considerations that play a significant role in the voltage selection decision-making process are not addressed in this paper. These 42 V inverters and motors are laboratory prototypes, not targeted to any specific vehicle