Fraunhofer System Research for Electromobility II

Since the beginning of 2013, more than 16 Fraunhofer Institutes are collaborating in the project  -  providing the multitude of needed interdisciplinary competences.

Three Fraunhofer institutes work on a fully automated wheel-propulsion unit within the cluster »Drive Train / Chassis«.This consists of an air-cooled wheel hub motor, an air-cooled traction inverter, a multi-level-DC/DC-converter, and an active chassis with a cooling air optimized wheel. The innovation is the coil with aluminum windings, which is built into an electric machine for the first time. The windings are manufactured using a precision casting and therefore have a high filling degree of the slots of over 80% and, through a good connection with the stator teeth, enable a high current density during operation despite the air cooling. The optimization of the configuration of the rims with regard to bettering the delivery of cooling air brings with it additional degrees of freedom concerning the heat dissipation from the wheel house. The rims are also designed while taking the requirements for operational stability into consideration. The 3H topology of the traction inverter offers apparent advantages concerning functional safety and reliability. The electric on board supply system functions with a nominal voltage of 48 volt, which can be increased as needed on the machine side below the boundary for low voltage to a maximum 120 volt using the multi-level-DC/DC-converter. This enables optimal efficiency in the operation of the wheel hub motor. Thereby, costly and extensive solutions regarding insulation monitoring for on board supply systems with nominal voltages of 400 volt are omitted.

The cluster »Battery / Range Extender« consists of seven Fraunhofer institutes that focus on building a battery system and the realization of a range extender module. The main focus of the work concerning the battery system is the advancement of single components and manufacturing techniques regarding light construction and efficiency. Examples of this include the development of a lightweight, yet crash resistant battery housing, cooling of the battery using PCM, and a mass production ready contact method for battery poles using laser welding. Another module is a compact, maximum efficiency battery called “Li-Booster” that can cover large power requirements in the on board supply system during impulsion as well as recuperation. This makes a two-part hybrid battery system with a noticeably longer lifespan possible, which consists of parts optimized for both the power stack as well as energy storage.

Different approaches are used for the “range extender” component. A compact fuel cell power module complements the “light construction energy pack” for a system optimized for energy conversion with zero local emissions to be used in electric vehicles. Another range extender module is being developed and optimized for use in light-duty commercial vehicles and light municipal vehicles. It is fueled by a reliable low-emission combustion engine in order to provide electric energy, as well as the necessary hydraulic energy.

Seven Fraunhofer institutes working in the cluster »Construction / Infrastructure« focus and work on research topics concerning efficient light construction of auto body structures, bidirectional inductive charging of electric vehicles, or automated driving. The main focus is the extensive functional integration of the individual components. An example is the integration into the floor assembly of a system for thermal management in the battery system and vehicle interior while taking into account the requirements concerning light construction and crash safety. Another main idea is the direct integration of manufacturing and production processes into technology development in order to implement decoupled, flexible, and highly integrated production systems in the future.