**5. Conclusions**

This paper proposes and investigates a single inverter-controlled brushless WFSM topology in which the inverter injects a three-phase armature current having a dc offset. In this arrangement, the volume of the machine can be reduced compared to a conventional brushless WFSM where an additional winding is used on the stator for excitation purpose. In addition, the proposed topology uses a single inverter and a simple current control strategy which makes it cost-effective compared to the brushless WFSM topologies of same kind. In particular, a 4-pole, 42-slot machine was used to simulate in JMAG for performance evaluation and verification of the working principle. The results show that a significant amount of torque is produced with the proposed brushless WFSM topology. This conclusion is, however, only based on the verification of the topology with reference to its working principle. The performance can be enhanced with an improved machine structure and optimized for various applications.

The limitation of the proposed single inverter controlled brushless WFSM topology includes the selection of the magnitude of dc offset for armature currents within a limit which may never cause any saturation for the stator and rotor cores.

**Author Contributions:** Conceptualization, S.S.H.B. and J.D.-G.; software, S.S.H.B. and G.J.S.; formal analysis, S.S.H.B. and S.M.; writing—original draft preparation, S.S.H.B. and A.A.M.; funding acquisition, J.-S.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Brain Pool (BP) Program funded by the Ministry of Science and ICT through the National Research Foundation of Korea (2019H1D3A1A01102988), the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education (2016R1D1A1B01008058), and the Human Resources Development (No.20204030200090) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) gran<sup>t</sup> funded by the Korea governmen<sup>t</sup> Ministry of Trade, Industry and Energy.

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

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