The powertrain concepts are characterized by using two smaller electric motors (EM) instead of one powerful electric motor. The electric motors are coupled to the drive shafts via a multi-speed transmission. The TDT concepts aim at achieving high overall efficiency based on shifting the load points by operating only one or both electric motors and using multiple gear ratios. Gear shifts are performed without interruption of traction force by using dog clutches instead of friction elements.
Based on the idea of multi-speed transmissions for pure electric vehicles, hybrid powertrain concepts are derived by adding an internal combustion engine (ICE) to the system resulting in a combined parallel-series hybrid powertrain configuration.
The specific design of the TDT with Range-Extender (DE-REX) is classified as dedicated Range-Extender transmission (DRT) combining the benefits of series hybrid Range-Extender Electric Vehicles and parallel Plug-in Hybrid Electric Vehicles.