Comparison of the electromagnetic performance of a flux-switching permanent magnet (PM) machine having two separate stators as well as different winding topologies is investigated in this paper. Different stator and rotor pole combinations of these machines are also considered. The analysis includes the open-circuit and on-load characteristics of the analyzed machines. It is observed that, the largest fundamental values of electromagnetic torque, for each winding topology, is seen in the 11-rotor-pole and 10-rotor-pole machines having alternate- and all-pole-wound configurations, respectively. Moreover, significant ripple is observed in the waveforms of the even-number rotor pole machines compared to their corresponding odd-number rotor pole counterparts. Overall, the alternate-pole-wound machines essentially have larger torque-density than their equivalent all-pole-wound ones. The investigated machine is also tested for validation.

A new double stator permanent magnet machine having two sets of alternating current (AC) windings in separate stators is proposed in this study. The proposed machine is appropriate for low-speed direct-drive applications. 2D- and 3D-finite element analysis (FEA) is adopted in the result predictions. The considered machine elements are: coil and phase flux linkage, coil and phase induced-electromotive force (EMF), copper loss, current density and torque characteristics. The analysis shows that the studied permanent magnet (PM) machine has better electromagnetic performance than its single-stator equivalent. Moreover, the proposed machine has potential for higher reliability if the separate stators are used independently. The effect of design parameters on open-circuit flux linkage and induced-electromotive force, as well as on the average electromagnetic torque of the proposed double stator machine is also presented. It is observed that for each of the investigated design variables, there is a need to select the optimal value in order to achieve the best average torque. The investigated design parameters are: the split ratio, magnet thickness, rotor radial thickness, inner stator tooth-width, rotor inner and outer iron-width/pitch ratio, and stator yoke size.

The electromagnetic and output performance characteristics of three (3) different types of double stator permanent magnet machines are quantitatively compared and presented in this study, in order to determine the most promising machine topology amongst the considered machine types, for potential practical applications(s). Two-dimensional (2D) and three-dimensional (3D) finite element analysis (FEA) methods are deployed in the computation of the performance metrics using ANSYS-MAXWELL software. The compared machines in this work are designated as: Machine 1, Machine 2 and Machine 3, respectively. The investigated machines have varying structural arrangements and two separate excitation sources. Machine 1 has its magnets situated in the outer stator with corresponding armature windings on both inner and outer stators. The magnets of Machine 2 are located in its inner stator while it has armature windings on both inner and outer stator parts. More so, Machine 3 is equipped with magnets in its inner and outer stators, though without armature windings on the inner stator section. The considered performance metrics include: inducedelectromotive force (induced-EMF), torque, power, demagnetization, losses and efficiency. The results show that the investigated Machine 3 has higher induced-EMF value and more sinusoidal electromotive force waveform than the other compared machines. Consequently, Machine 3 also has larger electromagnetic torque and power. Moreover, Machine 1 has the best flux-weakening potential, obtained from both the ratio of its maximum speed to base speed and the flux-weakening factor ( k_p).

The analysis of cogging torque, torque ripple and total harmonic distortion of a permanent magnet (PM) flux-switching machine having separate excitation stators is presented in this study. Further, the effect of unbalanced magnetic force (UMF) on the rotor of this machine is also investigated. A comparison of the analysed machine having different rotor pole configurations is also given. The analysis shows that the largest cogging torque, torque ripple as well as total harmonic distortion (THD) are obtained in the four-rotor-pole machine while the least of THD and torque ripple effects is seen in the thirteen-rotor-pole machine. Furthermore, the evaluation of the radial magnetic force of the machines having an odd number of rotor poles shows that the investigated machine having a five-rotor-pole number exhibits the highest value of UMF, while the smallest amount of UMF is obtained in an eleven-rotor-pole machine. Similarly, it is observed that the machines having an even number of rotor poles exhibit a negligible amount of UMF compared to the ones of the odd number of rotor poles.