Hyper-high-speed for electric vehicles to achieve maximum ranges.


Speed4E is the follow-up project of the already successfully completed research project Speed2E.
The general goal of Speed2E was the development, optimisation and setup of a high-rev-drivetrain, as well as the examination of its suitability for use in electrified automobiles. Increasing the driving speed of electric machines has the potential to significantly improve their power density and the overall efficiency of the vehicle.
Today’s electric vehicles are powered by machines with maximum driving speeds between around 10,000 rpm and about 15,000 rpm. With the increase in engine speed of up to 30,000 rpm, the volume of the active components, its mass as well as its price, could be reduced by about 30%. Therefore, the power density, the efficiency and the economic viability of electric automobile drivetrains were considerably raised.
The project objectives for Speed2E were accomplished: both sub-transmissions of the drivetrain were operated with a speed of up to 30,000 rpm, driving cycles could  be implemented and tested at the test-rig.


 Figure 1: Speed2E Drivetrain


Figure 1: Speed2E Drivetrain


In Speed4E, the goal is to reach and investigate even higher driving speeds,
in particular, driving speeds of up to 50.000 rpm are to be reached at the two test-rigs in Munich and Hanover, while a maximum motor speed of 30,000 rpm is pursued for safe operation in two vehicles. Hence, while developing a highly integrated, compact and power-dense drivetrain, a great focus will be put onto its NVH-behaviour and, especially, efficiency.

To achieve these ambitious goals, many aspects have to be taken into detailed account and, amongst others, these very challenges have to be faced:

  • Identification of a suitable sealing concept, since state-of-the-art solutions cannot be used with the investigated speeds
  • Design of bearings and their compatibility with the lubricant
  • Loss in the power electronics’ semiconductors and the airstream
  • Passing of multiple resonant frequencies of the gears
  • Generation of a highly integrated and scalable drivetrain
  • Development of a highly efficient lubricant and of an integrated thermal–management
  • Development of an intelligent transmission-management with matching control strategies
  • First-time integration and practical test in a vehicle

The project goals for the hyper-high-rev drivetrain are in particular:

  • Thanks to the hyper-high driving speed, a substantial contribution to raising the range and efficiency shall be given. Because of the application in a real vehicle, a compelling validation of the results is possible.
  • In addition to improving and optimising efficiency, intelligent operating strategies shall be developed for the complete system, which will benefit of the synergies of a highly integrated approach.
  • Design of a lightweight drivetrain for a further efficiency increase
  • First-time vehicle integration and testing of a hyper-high-speed drivetrain
  • Design of an innovative fluid to lubricate and cool all the components combined and development of an intelligent thermal-management
  • Realisation of a highly integrated and scalable drivetrain