Development of methodology for measuring efficiency in an electric vehicle propulsion unit

The automotive industry is facing a period of development of electric mobility that should bring several requirements together. Regulatory framework, environmental impact, new enabling technologies, customers' utilization and knowledge of the product are all aspects that should be considered during the development and testing phase of brand new vehicles. One of the main concerns is surely the driving range, which is declared by carmakers relying on test cycles such as WLTP for the European market. Although this number is important for comparing models on the market, it is not reflected in the real usage because the test cycle is not representative of the variability of the users' habits, but also because the powertrain components are tested in separated environments and the real system efficiency is below expectations. The joint venture between Stellantis and HBK produced a new approach: an integrated testing between motor and inverter using a power analyzer should theoretically reduce the gap between expected and actual results in the car range. The state of the art of electrified vehicles testing shows a huge variety of tests for stand-alone components, which are tested for their target performance and are usually pointed towards different directions. It is of paramount importance to know which are strengths and weaknesses in the conventional approach and how Stellantis has decided to address the problem through an experimental test method that is able to detect driveline power losses and efficiencies. The implementation is carried out using the combination of a HBK power analyzer and their software Perception eDrive for a powerful overview of the system thanks to a simple interface. This paper presents the methodology and the engineering solutions that are needed for an effective realization of the experiment, but also the problems that were faced throughout the process. The raw data that are generated by eDrive are post-processed offline to obtain the efficiencies of both stand-alone components and of the entire powertrain through a numerical calculation software. Results look promising as all the objectives can be achieved and the experimental data show a good correlation with the suppliers' ones.