Comparative Study on DC Winding Induced Voltage Pulsation of Wound Field Flux Modulation Machines Having Different Iron Core Structures

The wound field flux modulation machine (WFFMM) suffers from DC winding induced voltage pulsation, which can introduce pulsation in the DC winding current, deteriorate the machine performance and challenge the power supply. This paper aims to investigate the influence of iron core structures on the DC winding induced voltage pulsation of the WFFMM. Five different WFFMMs with different iron structures, including conventional WFFMM, partitioned stator WFFMM (PS-WFFMM), WFFMM with magnetic bridge, WFFMM with segmental rotor and variable flux reluctance machine (VFRM) are comparatively analyzed under current source excitation by finite element analysis and under PWM excitation by field-circuit co-simulation. It can be found that the PS-WFFMM exhibits the highest torque density, whilst its DC winding induced voltage is also the highest. The conventional WFFMM displays the second highest average torque and the smallest amplitude of baseband harmonics under PWM excitation. The WFFMM with segmental rotor and WFFMM with magnetic bridge displays low DC winding induced voltage, whilst they also exhibit the lowest torque density among the different topologies. The VFRM is characterized as highest power factor among the different topologies. The prototype of the optimized 12-stator-slot/10-rotor-pole VFRM is built and tested to validate the comparative analysis.