Comparative Study of Stator Electrically Excited Machines with and Without Dual-Armature Windings

To meet the demand for high torque density in applications such as actuators, this paper investigates the use of dual-armature (DA) windings on both stator and rotor to enhance torque performance for stator electrically excited machines. A systematic comparison is conducted among four topologies, namely the conventional flux-switching electrically excited (FSEE) and variable flux reluctance (VFR) machines, as well as their DA counterparts. All machines are optimized under the same copper loss and torque ripple constraints to ensure a fair comparison. The results show that the FSEE machine delivers approximately 49% higher torque than the VFR machine, attributed to its higher stator back-EMF. By integrating the rotor armature winding that fully utilizes the rotor space, the DA-FSEE and DA-VFR machines achieve substantial torque improvements of 81% and 163%, respectively. While the DA-VFR machine shows the most pronounced torque enhancement, the DA-FSEE machine provides the highest-torque output. Benefiting from the improved torque performance, the DA-FSEE and DA-VFR machines also demonstrate 10–20% higher efficiency over their counterparts within a typical speed range. Furthermore, sensitivity analysis of key design parameters reveals that the split ratio has the most profound influence on torque output for all the machines, followed by the stator tooth width. In the DA machines, the rotor yoke thickness emerges as a consistently important factor for achieving high torque performance. These key findings provide valuable guidance for the optimal selection and detailed design of high-performance electrically excited machines in engineering practice.