**6. Discussion**

An analytical as well as an experimental approach are performed to study the influence of the silicon and aluminum content of soft magnetic materials on their thermal conductivity. The two approaches show very good agreement for a majority of the studied materials and analyzed temperatures. The thickness of the probes is identified as a crucial factor for the accuracy of the measurements. The validity of the experimental values of the thin samples M8 is restricted. The results indicate a significant influence of the alloying

contents on the thermal conductivity of the materials. A simplified case study is performed. The maximum possible heat that can be extracted from the rotor and stator of a reference induction machine varies by a factor of up to four for the different materials. It is obvious that this factor should be considered in the design process of high power density traction drives in the case that a main heat dissipation path is realized over the lamination of the machine.

A measurement of a thicker material with a very high silicon content would be helpful to further identify whether the introduced formula needs to be adjusted for such alloys. In a real application, additional thermal resistances would be present that reduce the calculated impact on the thermal dissipation. The different materials, of course, also influence the magnetization behavior and the produced losses in the material. The selection of the material should consider all these aspects. Detailed measurements of the loss behavior of the studied materials, a thermal model of the studied motor, a test bench evaluation of the entire motor and a simulation study including thermal, loss and magnetization aspects is on the way.

**Author Contributions:** Conceptualization, B.G, A.R., N.L. and K.H.; methodology, B.G. and A.R.; software, B.G. and A.R.; validation, B.G., A.R. and N.L.; formal analysis, B.G. and A.R.; writing original draft preparation, B.G.; writing—review and editing, B.G., A.R., N.L. and K.H.; visualization, B.G. and A.R.; supervision, K.H.; project administration, K.H.; funding acquisition, K.H. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research and development project "Concept-ELV2(01MY17002B)" is funded by the German Federal Ministry for Economic Affairs and Enegry (BMWi). The authors are grateful to the BMWi for the financing of this collaboration and who are responsible for the contents of this publication.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** We want to thank the Institute for Materials Applications in Mechanical Engineering (iwm) of RWTH Aachen University and Netzsch Gerätebau GmbH for the excellent consultation and discussion within the project.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
