Novel Sub-Harmonic-Based Self-Excited Brushless Wound Rotor Synchronous Machine

Abstract

This article aims to realize a self-excited wound rotor synchronous machine (WRSM) topology established while considering the subharmonic field excitation scheme. Unlike the conventional subharmonic-based brushless WRSMs that require a dual-inverter configuration, the proposed topology uses a single inverter and a dual-armature winding pattern. The employed dual-armature winding configuration involves a four-pole main armature winding (ABC) and a two-pole open winding (X). The ABC winding is supplied with a three-phase current from a single customary current source inverter (CSI), whereas the X winding carries no current due to its open winding pattern and is responsible for generating subharmonic magnetomotive force (MMF) in the air gap along with the fundamental-harmonic MMF. The fundamental-harmonic MMF is utilized to create a four-pole stator field, while the subharmonic MMF is used to induce the harmonic current in the two-pole harmonic winding of the rotor. The generated harmonic current is rectified to energize the rotor field winding and develop a four-pole rotor field. The electromagnetic interaction of the four-pole stator and rotor fields generates torque. As the proposed subharmonic-based self-excited brushless WRSM employs a single inverter for its brushless operation, this makes it cost-effective compared to the conventional dual-inverter subharmonic-based brushless WRSM topologies. The proposed self-excited brushless WRSM topology is validated through the finite-element analysis (FEA). JMAG-Designer tool is employed to carry out FEA for a four-pole, 24-slot (4p24s) machine. The quantitative relative performance evaluation of the proposed self-excited WRSM topology with the recently developed dual-inverter-controlled subharmonic-based brushless WRSM topology is presented to show its better performance in terms of average, maximum, and minimum torques and torque ripple.