**6. Conclusions**

This paper discusses various aspects of the optimal design of a traction SHM, applying the one-criterion unconstrained Nelder–Mead method. This SHM is intended for use in a mining dump truck with a carrying capacity of 90 tons.

The objective function for the SHM optimization was designed to reduce/improve the following main characteristics: total motor power loss, maximum winding current, and torque ripple. Optimization was carried out by taking into account the characteristics of the SHM at three loading modes. The constraints of the supplied voltage and of the maximum magnetic flux density in the nonlaminated parts of the magnetic core were imposed.

Among the varied parameters, after the optimization, the air gap width changed most significantly; it increased 1.4 times, which makes it possible to reduce the saturation of the magnetic circuit, reduce the reactive power of the motor, increase the reliability of the motor, simplify assembly, and also to reduce the torque ripple.

As a result of optimization, in the motor mode, at operating points 1 and 2, the total losses reduced by 1.13 and 1.16 times, respectively. At operating point 3, only a slight reduction in the total losses was achieved. At operating points 1 and 2 of the motor mode, the symmetrized torque ripple reduced by 1.45 and 1.32 times, respectively. The flux density in the nonlaminated parts of the magnetic core reached a maximum value of 1.65 T at operating point 3. The maximum armature winding current in the motor mode decreased by 8%. In the braking mode, the total losses of the SHM were also significantly reduced after optimization, although this operating point was not optimized and was not included in the objective function.

In addition, after the optimization, the regions of the motor magnetic core with extreme saturation noticeably decreased, which is one of the reasons for the decrease in losses and an increase in efficiency.

In future works, the SHM will theoretically be considered in other applications, for example, as a traction motor for a light electric vehicle and electric bus. In addition, a theoretical comparison of the SHM with a traction induction motor will be carried out.

**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 No. 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.
