Combined Regulation Performance Research of the Novel Flux-Torque Regulation Hybrid Excitation Machine With Axial-Radial Magnetic Circuit

Flux-weakening control is usually used for permanent magnet synchronous machines (PMSMs) to operate above the rated speed, which will cause a high $d$ -axis current and torque decline. So, a novel flux-torque regulation hybrid excitation machine (FTRHEM) with an axial radial magnetic circuit is presented in this article, which can provide additional torque by the axial alternating magnetic motive force (MMF) and solve the disadvantage of reducing the torque at the flux-weakening. To better clarify the principle of the machine, the air-gap magnetic flux and torque equations are deduced by combining the machine operating states and the equivalent magnetic network model. The coupling relationship between the axial and radial magnetic circuits is analyzed to figure out the key factors affecting the flux and additional torque. Then, the influence mechanism of excitation current (EC) on magnetic flux and torque performance is clarified. The maximum flux regulation range and output torque of this machine are analyzed separately. The maximum flux regulation is 19.1%, and the torque increases by 48.1% more than that without excitation. Finally, the mechanism for matching EC with different torque and flux is determined. Experiments have been carried out to validate the analysis above.