Development of the Separately Excited E-Machine Topology I2SM for a Sustainable, Compact and Efficient Powertrain for Future E-Vehicles

Authors

C. Sasse, M. Beringer, ZF Friedrichshafen AG, Schweinfurt:

Year

2024

Print Info

Production/Publication ÖVK

Summary

Uncertainties in the supply chain and sustainability targets have a drastic effect on the electromobility technology landscape. In this context, ZF has further developed the already sustainable and magnet-free e-machine topology of the separately excited synchronous machine (SESM). By deploying a highly integrated inductive exciter and using far-reaching system approaches it is an alternative to conventional permanently excited synchronous machines (PSMs). The so-called I²SM (In-rotor Inductively Excited Synchronous Machine) combines supreme efficiency and power density. Additionally, the design no longer requires magnets and the critical rare earths elements they contain. Based on the I²SM approach, the CO₂ footprint (upstream) can be reduced by 50 % compared to typical permanent magnet synchronous machines. One of the key improvements of the I²SM concept is based on the smaller size of the transformer (up to 90 mm smaller compared to conventional slip ring systems). The inductive transformer is located inside the rotor shaft and is arranged entirely in the oil chamber and therefore without seals. This gain in installation space creates further efficiency potentials in the overall system. Furthermore, inductive power transmission does not require any friction elements, such as carbon brushes or radial shaft seals, which reduces mechanical losses and ensures wear-free operation.

This paper describes the advantages of ZF’s I²SM compared to the permanently excited synchronous machine, which is currently the standard e-machine for primary drives. In addition, further applications of the I²SM in an EV will be presented. Its very high efficiency at high vehicle speeds makes the I²SM the ideal choice as a primary drive. It also has good potential as the secondary drive in all-wheel drive EVs, which was previously reserved for other drive concepts.

ISBN

978-3-9504969-3-2

DOI

https://doi.org/10.62626/3gwx-xs4p Copy link