**6. Conclusions**

Inadequate design methods for synchronous homopolar machines (SHMs) can result in the need to significantly overrate the installed power of the traction inverter in applications requiring operation over a wide constant power speed range. This article discusses the novel procedure and results of optimization of the commercially available 370 kW traction SHM using the Nelder–Mead method. The objective function was composed to improve/minimize the basic characteristics of the traction SHM, such as the total motor power loss and maximum armature winding current. To obtain the feasible optimized design, necessary constraints were imposed. As a result of the optimization, the motor losses and the maximum current required by the motor from the inverter were significantly reduced. The achieved reduction in the maximum current allowed the cost of the IGBT modules of the inverter to be reduced by 1.4 times (by \$2295), and also allowed a reduction of the AC component of the DC link current.

**Author Contributions:** Conceptual approach, A.A., V.D. and V.P.; data duration, V.D. and V.K.; software, V.D. and V.P.; calculations and modeling, A.A., V.D., V.K. and V.P.; writing—original draft, A.A., V.D., V.K. and V.P.; visualization, V.D. and V.K.; review and editing, A.A., V.D., V.K. and V.P. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was performed with the support of the Russian Science Foundation gran<sup>t</sup> (Project № 21-19-00696).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data are contained within the article.

**Acknowledgments:** The authors thank the editors and reviewers for their careful reading and constructive comments.

**Conflicts of Interest:** The authors declare no conflict of interest.
