Torque ripple reduction in brushless wound rotor synchronous machine by two-phase excitation winding

Abstract

This paper presents a research on reducing the torque ripple in a brushless wound rotor synchronous machine (BL-WRSM). The basic brushless topology generates a third-harmonic current component in the stator to excite the rotor. The rotor has two types of windings, field winding and harmonic winding, which are connected with each other through a rotor mounted diode rectifier. Field winding has same number of poles as that of the stator armature winding to generate torque while the harmonic winding has three times the number of poles as that of the armature winding, to induce third harmonic current component and excite the field winding. In this paper, the rotor harmonic winding is split in two branches and further a capacitor is connected in series with one branch to create a phase difference. Phase difference between the two harmonic winding branches reduces the peak-to-peak value of the DC current fed to the field winding and hence the torque ripple is reduced. Finite Element Analysis (FEA) is performed to verify the reduction in ripple percentage.