Electrification of vehicles has a good momentum today. However, energy consumption of electrified vehicles is not very much in focus, instead the society is just happy for the electrification to take place. In the future, however, the focus on the energy efficiency of electrified vehicles will for sure be intensified.

In this joint effort between the Division of Electrical Power Engineering as well as the Division of Fluid Dynamics, one of the most lossy parts in an electrical drive train – the combined gear-box-electric machines package – will be investigated. The purpose is to find new solutions, the hypothesis is with another gearing, which will give reduced energy losses and still have an acceptable material usage.

Electrification of vehicles has a good momentum today. However, energy consumption of electrified vehicles is not very much in focus, instead in-efficient electrified vehicles are appreciated on the cost of more energy efficient ICE vehicles. There is talk about a ‘nordic energy mix’, but still almost every single extra kWh of electric energy put in an electrified vehicle in Scandinavia, must be generated by fossil fuels. This needs to come to an end, when electrified vehicles become more and more common. In a recently conducted research project [Vehicle – Energimyndigheten project 41213] it was identified that the gear-box has the same loss as the electrical machine. The gearbox is usually a two-stage gearbox, with a gear ratio of 8-12. If a single stage gear-box could be used, the efficiency would go up, however, then the electric machine becomes larger. No gear at all gives best efficiency, but a very large electrical machine. In principle, 1500 rpm at top speed with a power of 100-150 kW is what is needed.

The purpose of this project is to optimize the electric machine-gear package to find a system solution that has the highest efficiency, but still reasonable size. The hypothesis is that by a careful design of the gearbox, selection of more viscous oil, but still suitable to maintain the life-time of the gear in combination with an adapted machine design will lead to important loss savings in the transmission of an electrified vehicle.

Project time: Jan 2019 – Dec 2020