Integrated Drive Inverter for Wheel Hub Motors

Project targets

In the context of the project ’FSEM - Fraunhofer Systemforschung Elektromobilität’ a drive inverter for the application in wheel hub motors with a DC-link voltage of 400 V was developed at the Fraunhofer IISB.

Short description

The drive inverter that is fully integrated into the wheel-hub motor generates a frequency variable alternating current out of the direct current of the traction battery (nominal DC-link voltage = 400 V). Thus, a continuous power of 30 kW and a peak power of 65 kW are available at each motor. The drive inverter located between battery and motor and developed at IISB for this application is integrated into the external rotor motor without requiring additional construction space. The integration of the drive inverter into the motor offers the possibility of a common use of the existing motor cooling circuit. The expected electromagnetic emissions should be reduced because of the shielding effect of the metallic motor housing in which the drive inverter is placed. The structure of the system is redundant because of its realization as two three-phase partial machines in one wheel-hub motor. If one motor or one phase fails, the system can be operated with half power.


Special demands concerning construction, contacting and thermal behavior are made regarding the integration of power electronics into the motor. High requirements concerning robustness and vibration resistance of the drive inverter are necessary because of the integration into the unsprung area of the vehicle. All loads occurring to the wheel directly affect the drive inverter. To meet these high requirements among others, the power connections to the DCBs have been realized with wire bonding. By means of thermal simulations of motor and drive inverter during the development phase, the thermal behavior of the system has been characterized and optimized in advance.

Project duration



H. Rauh, M. Hofmann, B. Eckardt, M. März: Radantrieb und Zentralantrieb – innovative Antriebskonzepte im Vergleich. Tagungsband ‚Haus der Technik - Trends in der elektrischen Antriebstechnologie für Hybrid- und Elektrofahrzeug (Expert Verlag)‘, München, 2011.