Operation Strategy with Thermal Management of E-Machines in Pure Electric Driving Mode for Twin-Drive-Transmission (DE-REX)

The innovative powertrain concept of twin-drive-transmission has two identical electric machines and two separate sub-transmissions with two gear ratios. To increase the driving range, an additional internal combustion engine is used as a range extender. Thus the vehicle can get the traction force in pure electric mode as well as in parallel and series hybrid modes. For this powertrain concept, an interior permanent magnet synchronous machine was designed and constructed. The electrical machine was measured on the test bench. The measured efficiency of the prototype E-machine with a commercial inverter is shown in this paper. The energy consumption of the vehicle is affected by the efficiency of the E-machines, especially in pure electric driving mode. The ohmic losses, which are the main losses in the E-machine, depend on the temperature of the stator winding. Thus by applying the thermal management of the two E-machines to the operation strategy of the twin drive, it is possible to select a proper driving strategy in pure electric driving for minimized energy consumption. Simulated and partially measured results with the proposed and the original operation strategy in pure electric driving mode are compared in this paper.