Hybrid Traction Unit

Project Targets

Electric drive unit with two independent induction machines and an integrated double inverter for the use in axle-split hybrids or small electric vehicles.

Short Description

The developed integrated drive unit includes two induction machines with a nominal power of 20 kW for each motor and a maximum torque of 80 Nm up to a motor rotational speed of 2500 1/min. Two planetary reduction gears (ratio 6:1) are used to achieve the required torque of about 500 Nm at each wheel. Each of the two mechanical independent motors powers one wheel of the electrified axle with an individual torque regulation realized by two implemented field oriented controls (FOC) running on the system's control board. Due to the compact system design, the drive unit can be installed in the rear axle at the installation space that is, e.g. in a 4WD car like the Audi TT quattro, originally intended for the mechanical differential. Depending on the used energy storage, the system is suitable for small electric vehicles or for hybrid vehicles with a conventional combustion engine powering the other axle of the car (axle-split hybrid).

The unit’s double inverter is installed directly at the housing of the electric machines and uses a common cooling jacket with the motor for the six half-bridge IGBT modules. The control board, which is based on the Infineon TricoreTM, and the common DC link foil capacitor for both inverters are placed above the power-modules.

The specifications of the integrated double inverter are:

Apparent output power (each inverter): 45 kVA

Switching frequency: 10 kHz

Nominal DC link voltage: 400 V

DC-link capacitor: 0.5 mF

Direct cooled DCB/DAB substrates (ECPE/FhG WO 2007/090664)

Infineon IGBT 3

Infineon EmConTM diodes

AC-current measurement: open loop hall effect sensors

Project Partners

Oswald (E-Motors, Miltenberg)

Heynau (Planetary gears, Landshut)

Project Duration



M. Hofmann, H. Rauh, B. Eckardt, A. Schletz, M. März: Mechanische Integration von Leistungselektronik in die Antriebseinheit eines Axle-Split-Hybrids. Tagungsband ‚Haus der Technik - Praxis der elektrischen Antriebe für Hybrid- und Elektrofahrzeuge (Expert Verlag)‘, München, 2009.

M. Hofmann, B. Eckardt, M. März, L. Frey: Effizienzoptimierung integrierter elektrischer Antriebssysteme für Hybrid- und Elektrofahrzeuge. Tagungsband ‚Elektro Mobil Ausstellung 2010‘, Aschaffenburg, 2010.

M. Hofmann, B. Eckardt, M. März, L. Frey: Thermal Characterization of an Axle-Twin-Drive with System Integrated Double-Inverter. IEEE proceedings ‚1st international Electric Drives Production Conference’, Nürnberg, 2011.