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To meet the specific requirements of electrically driven passenger cars, Steyr-Daimler Puch Fahrzeugtechnik (SFT) has developed an advanced, optimized drive train integrating both functionally and physically the components of electric motor, electronic control, charging system, transmission, and final drive. Subject of this paper is the design and function of the transmission system. Most of the state of the art EV drive systems are designed with a single transmission ratio. This, however, leads to high peak currents, a heavy electric motor, and inefficient use of the battery energy to achieve sufficient gradeability, traction, and acceleration. To avoid these disadvantages, SFT has developed a transmission system with a low gear for low speed/high traction conditions, and a high gear for normal driving. Gear shift between low and high is fully automatic, and carried out by an electric actuator.

To meet the specific requirements of electrically driven passenger cars, Steyr-Daimler-Puch Fahrzeugtechnik Ges.m.b.H. (SFT) has developed an advanced, optimized drive train integrating both functionally and physically the components of electric motor, electronical control, charging system, transmission, and final drive. Subject of this paper is the design and function of the overall system and the electronic control unit in detail. A fully integrated concept for the electronic control unit including motor control, charger, DC/DC-converter, and battery and system management was found as the only way to achieve the cost and performance targets for a state-of-the-art EV-drive train. Vehicle safety requirements for ECU have been taken into consideration as well. A first installation in a VOLKSWAGEN GOLF was done for testing and evaluating. First results showed very good performance of the overall system and comfort for the driver.