Investigation of field regulation characteristic of a hybrid excitation synchronous machine with axial auxiliary air-gaps

A new hybrid excitation synchronous machine (HESM) with axial auxiliary air-gaps is proposed. The architecture and operation principle of the HESM are presented. 3D finite-element analysis (FEA) models of the HESM are established, and finite-element analysis is performed to achieve the magnetic field distribution, air gap flux density and the magnetic field regulating characteristic of electrical MMFs. A comparative study between the HESM with axial auxiliary air-gaps and the HESM with radial auxiliary air-gaps is presented. Optimized method is proposed to increase the field regulation range. The results indicate that the proposed HESM has good performance of flux regulation capability as well as the HESM with radial auxiliary air-gaps, furthermore, it has some other benefits in structure, such as the larger spaces to embed excitation coils.