A novel rotor harmonic winding-based high efficient self-excited brushless wound rotor synchronous machine with improved torque features

The limited availability and high cost of permanent magnet (PM) materials have drawn the attention of researchers toward PM-free and hybrid machines. Brushless wound rotor synchronous machines (BLWRSMs) have gained significant popularity among these machines. These machines require less maintenance because they do not use carbon brushes, slip rings, and an external DC source. This work introduces a novel self-excited BLWRSM configuration based on a dual harmonic winding (HW). Unlike the existing BLWRSM design using a single HW, the proposed configuration effectively utilizes the unused space within the rotor slots of the existing model. It introduces an additional HW on the rotor to carry alternating current induced by the inherent subharmonic component generated within the stator magnetomotive force. A series capacitor is added to the dual HWs to ensure their currents are in phase. The alternating current of dual HW is rectified via a rotor-mounted rectifier to supply the required direct current excitation to the rotor field winding for the generation of rotor magnetic field. The addition of extra HW contributes to an increased field current, which significantly improves the torque features of the proposed motor. Finite element analysis is used to verify the proposed design in JMAG-Designer version 18.1 software. The obtained results demonstrate that, when both machines operate with the same magnitude of stator winding current, the machine being proposed exhibits a 22.15% improvement in average torque in comparison with the existing model, making it a potential substitute for high-torque applications.