Brushless Operation of a Wound-Field Synchronous Machine Using a Novel Winding Scheme

This paper proposes a novel winding scheme to generate an additional sub-harmonic magneto-motive force (SH-MMF) component for the brushless (BL) operation of a wound-field synchronous machine. The existing SH generation schemes for BL operation use a dual inverter or a single inverter with asymmetrical winding and low slot fill factor in half of the stator. The proposed scheme comprises a single inverter with symmetrical stator winding distribution and the same fill factor for all stator slots. The generated additional SH-MMF component in the proposed scheme is induced in the harmonic winding wound on the machine rotor. A rotating bridge rectifier mounted on the rotor periphery connects the rotor harmonic winding with the rotor field winding, and rectified dc is supplied to the rotor field winding. The 2-D finite-element analysis (FEA) was carried out to analyze the principle, and the FEA predictions were experimentally validated.