Brushless Operation of Axial-Flux Wound-Rotor Synchronous Machine Utilizing Third Harmonic

The brushless operation presented in this study is of an axial-flux wound-rotor synchronous machine (AFWRSM) which uses the third harmonic and the fundamental components of current. The proposed brushless AFWRSM utilizes a single inverter configuration; there are two windings on the rotor surface, i.e., field and harmonic windings, connected using a diode rectifier. The harmonic winding holds twelve poles, and the field winding consists of four poles, whereas the stator consists of a balanced three-phase, four-pole winding designed using 36 slots. A current source inverter (CSI) is utilized to inject both the fundamental and third-harmonic currents in the stator winding. This arrangement generates a third harmonic in the air-gap of the machine, which is used to induce voltages in the harmonic winding. The proposed AFWRSM brushless operation is validated using 3D finite element analysis (FEA).