Comparative analysis of variable flux reluctance machines with double- and single-layer concentrated armature windings

In this paper, the variable flux reluctance machines (VFRMs) with double- and single-layer concentrated armature windings are comparatively analyzed. Firstly, the single-layer winding is found to have identical winding factor as double-layer winding, but significantly larger peak value of magneto-motive force, which will result in severe local saturation in cores of VFRMs with single-layer winding. Then, based on the magnetic gearing effect and finite element analysis, the electromagnetic performances of VFRMs with both winding types are compared. The VFRMs with single-layer winding are proved to be always lower in average torque and higher in torque ripple than those with double-layer winding. Overall, the double-layer armature winding is the preferable choice for the VFRMs. Finally, a 6-stator-slot/4-rotor-pole VFRM prototype with both double- and single-layer windings is tested to verify the findings.