In this paper we present an effective analytical modeling approach for the design of the transmission of electric vehicles. Specifically, we first devise an analytical loss model for an electric machine and show that it can be accurately fitted by only sampling three points from the original motor map. Second, we leverage this model to derive the optimal transmission ratio as a function of the wheels' speed and torque, and use it to optimize the transmission ratio. Finally, we showcase our analytical approach with a real-world case-study comparing two different transmission technologies on a BMW i3: a fixed-gear transmission (FGT) and a continuously variable transmission (CVT). Our results show that even for e-machines intentionally designed for FGT, the implementation of a CVT can significantly improve their operational efficiency by more than 3%. The provided model will ultimately bridge the gap in understanding how to efficiently specify the e-machine and the transmission technology in an integrated fashion, and enable to effectively compare single- and multi-speed-based electric powertrains.
|Title of host publication||2020 IEEE Vehicle Power and Propulsion Conference, VPPC 2020 - Proceedings|
|Publisher||Institute of Electrical and Electronics Engineers|
|Number of pages||6|
|Publication status||Published - 18 Feb 2021|
|Event||17th IEEE Vehicle Power and Propulsion Conference (VPPC 2020) - Virtual, Gijon, Spain|
Duration: 18 Nov 2020 → 16 Dec 2020
Conference number: 17
|Conference||17th IEEE Vehicle Power and Propulsion Conference (VPPC 2020)|
|Abbreviated title||VPPC 2020|
|Period||18/11/20 → 16/12/20|
Bibliographical notePublisher Copyright:
© 2020 IEEE.
Copyright 2021 Elsevier B.V., All rights reserved.
- Automated transmissions
- Continuously variable transmission
- Electric machines
- Electric vehicles