## 5 Conclusions  
In this research, the design study of the 45 kW-class MG-PMSM was conducted for the application of the MG-PMSM to the driving system for a tram. Since the MG-PMSM must be installed in the bogie space where the conventional mechanical reduction gear system is mounted, minimizing the size of the MG-PMSM was the main design goal in this research. First, to derive the detailed model of the 45 kW-class MG-PMSM for the tram, the analysis of the characteristics according to the stator winding method (distributed and concentrated windings) was performed. In the case of the MG-PMSM with the distributed winding, there was a problem where the axial length of the MG-PMSM did not satisfy the requirements due to a large end-turn part. After selecting the concentrated winding method that could reduce the end-turn size of the MG-PMSM, two design topologies were applied to determine the number of stator poles, the number of outer rotor pole pieces, and the number of inner rotor poles of the MG-PMSM. The final selected design topology is a method of using the number of pole pairs of the stator to derive the number of pole pieces, and the detailed model design was conducted to verify the design topology. The detailed model was derived by applying the selected design topology that can minimize the size of the MG-PMSM. In conclusion, through the detailed design of the final model, the rated current of the 45 kW-class MG-PMSM with concentrated winding could be reduced by 23% and the volume by 9.5%, and the efficiency could be increased by 0.2%.  
In addition, the 4.5 kW-class small-scaled MG-PMSM prototype with concentrated winding was fabricated to verify the validity of the analytical model, and performance verification was performed. The validation of the design method and parameters were verified through the no-load and load performance test of the MG-PMSM prototype. Although the rated load test could not be conducted due to instability due to the eccentricity of the pole pieces rotor, the dynamic performance of the MG-PMSM prototype was derived through the light load test and compared with the FEM simulation results. In conclusion, the effectiveness of the design method of MG-PMSM presented in this research is partially verified through the light load test results of the 4.5 kW-class small-scaled MG-PMSM prototype. In the future, we plan to additionally proceed with the rated load test through the modification of the pole pieces rotor.  
Conceptualization, C.-B.P.; methodology, C.-B.P. and H.-W.L.; software, J.-H.L. and G.J.; validation, J.-B.L. and J.-S.L.; formal analysis, J.-H.L. and G.J.; investigation, C.-B.P.; writing--original draft preparation, J.-H.L.; writing--review and editing, C.-B.P.; visualization, J.-H.L.; supervision, C.-B.P.; project administration, C.-B.P.; funding acquisition, C.-B.P. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the Korea Agency for Infrastructure Technology Advancement (KAIA) grant funded by the Ministry of Land, Infrastructure and Transport (Grant 21 RSCD-C163329-01).  
Not applicable.  
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.