Drivetrain architectures and their impact on the choice of the electrical machine

Summary form only given. Hybridization of passenger vehicles is about to become a significant business among carmakers and suppliers. This will start in a couple of months in the premium class and will arrive, step by step, in the high volume classes. This process is often referred to as the migration of electric drives in cars. However, a paradigm change from hybrid to electric cars is not achievable by the technology used in hybrid cars. This is due to the significant difference between electric drives when working jointly with combustion engines and drives in purely electric driven cars. Although electric drives are very often associated with battery EV´s, it just refers to the fact that there is no other mechanical propulsion but an electric machine. The global efficiency now becomes an economic factor, because any energy conversion into mechanic power is now electric. But even more important is the drag loss of the free-wheeling motor, because any loss in this condition will be integrated along the drive path. Hence the specification of an electric machine in a main drive is totally different from the packaging driven torque per volume specification of a hybrid motor. Due to the absence of clutches and shift gears, a permanent form closed connection between the electric machine and the drive axle(s) is provided. Safety standards require that there is no unexpected braking and no unintentional torque provided even under fault conditions in any component of the electric or electronic power conversion system. It will be shown that this also implies intrinsic safety properties of the electric machine, which is not provided by most of the designs which are currently used in hybrid cars. The lecture presentation deals with the intrinsic limitations and safety properties of different electric machines and how this can be influenced by the magnetic design. The consequences on the road will be explained by a simple system integration example.