Winding configurations and performance investigations of 12-stator pole variable flux reluctance machines

This paper presents an analysis of winding configurations in the novel 12-stator pole variable flux reluctance machines (VFRMs), which employ a doubly salient structure with stator located DC field windings. Compared with other doubly salient machines, including switched reluctance machines (SRMs) and doubly-fed doubly salient machines (DFDSMs), the winding connections are not fixed in VFRMs due to more feasible stator/rotor combinations. For VFRMs with 12-stator poles, both unity and non-unity winding distribution factors can be obtained. For example, in 11- and 13-rotor pole machines two types of winding connections can be used, but having different distribution factors. Due to the elimination of even order harmonics and significant reduction of the 5th and 7th order harmonics in the flux-linkage, negligible cogging torque and torque ripple (<;2%) can be obtained in the 11-rotor pole machine with an appropriate winding configuration. This is a further improvement of VFRMs with non-unity distribution factor compared with the machines with a unity distribution factor. In addition, compared with the 10-rotor pole machine, only a slight reduction of average torque in the 11-rotor pole machine is sacrificed. Five prototype VFRMs with a 12 pole stator and different rotor poles designs have been manufactured and used for the verification.