With major OEMs getting increasingly involved in the Formula E race series, many are using it as an opportunity to push development of cutting-edge electric motor and inverter technology. In the case of Audi, it has taken the unusual step of making public details of the powertrain that will be fitted to its FE07 contender.
“The Audi e-tron FE07 has an all-new electric powertrain that was developed in-house for the first time,” explained Stefan Aicher, head of development, e-Drive, at Audi Sport. While in recent years a continually optimized version of the powertrain, jointly developed with technology partner Schaeffler, was always used, work on the new MGU and inverter unit for the coming world championship started from scratch. “We went to the limits in all areas of this project,” added Aicher.
The result is called the Audi MGU05, a six-phase, motor-based, single-speed drivetrain with an internal rotor concept, external magnets and high-efficiency cooling system.
According to Aicher, Audi has managed significant weight savings compared with the previous unit, through the use of lightweight materials and intelligent integration with the vehicle. “We were able to directly reinvest these savings in the new MGU for the benefit of enhanced efficiency. Even so, the new MGU inverter unit weighs less than 35kg. This was an exceptional achievement by the whole team,” he noted.
Efficiency is a key factor for success in Formula E. “That is why we are leaving no stone unturned to reduce the energy loss within the system to an absolute minimum,” said Tristan Summerscale, Formula E project leader at Audi Sport.
Summerscale remarked that through extensive test bench development, over numerous testing cycles, “We have achieved an overall efficiency of more than 95% for our powertrain. The new MGU inverter unit has an efficiency of more than 97% in all relevant driving conditions.”
The compact size combined with high performance is particularly impressive. “If you compare our MGU with an internal combustion engine delivering a comparable power output of 250kW, our efficiency is not only twice as high, but our weight of less than 35kg is also much lighter,” added Summerscale. “This clearly shows what an efficient solution an electric powertrain is.”