This paper models a huge family of electrical machines featuring simple salient poles in a unified way based on the general airgap field modulation theory. The modulation principle is analyzed by introducing the magnetomotive force (MMF) modulation operator, which characterizes the influence of variable reluctance block on the primitive magnetizing MMF distribution established by field winding. Popular machine topologies are investigated in detail from the perspective of airgap field modulation mechanism. The iron core magnetic potential drop due to the finite slot opening depth and the impact of iron saturation on the parameters are considered by proper theoretical indication. In addition, the modulation effect of salient poles highly depend on the slot-opening-width- to-pole-pitch ratio $\epsilon$. The effect can be neglected when $\epsilon$<0.3 and the best modulation results will be achieved when $\epsilon$=0.5. It is also found that mainly three different harmonics parts modulated by salient poles contribute on airgap flux density and torque production. Straightforward relations between the frequency-domain or amplitude information of performances indexes and topological parameters can be obtained obviously by certain analytical expressions without heavy finite-element analysis (FEA). Analytical results are verified by 2D FEA and experiments measurements.

To address both single open-switch fault (OSF) and arbitrary two OSFs of a five-phase permanent magnet synchronous motor (PMSM) drive, a generalized fault-tolerant model predictive current control method is proposed in this article. Firstly, the postfault currents under OSFs are analyzed in the stationary frame based on the Fourier method. Then, to maintain torque output capacity and alleviate torque ripple, the optimal reference currents in fault scenarios are deduced with the principle of rotating magnetic motive force undisturbed. Further, the obtained phase currents are transformed into the rotating frame and applied in the cost function for the voltage vector optimization. Thus, the torque under post-fault operations is guaranteed and the torque ripples are suppressed. Finally, various experiments are conducted to validate the feasibility of the generalized fault-tolerant control method of five-phase PMSM drives.

Permanent-magnet (PM) motors have been widely used in industrial applications and automobiles. However, owing to the design tolerances, manufacturing uncertainties, and material inconsistency, deviations from the ideal motor inevitably occur with parasitic effects, such as additional cogging torque and vibration. One of the most significant obstacles for evaluating these uncertainties is the large computational burden caused by the countless uncertain combinations, which must be computed via the finite-element method (FEM). Herein, a worst—uncertain—combination—analyze (WUCA) method is proposed to significantly reduce the computational cost. A widely used analytical method is modified to identify the origin of additional cogging-torque harmonics caused by uncertainties. Different types of uncertainties for the surface-mounted PM machine and interior PM machine can be analyzed simultaneously. With the WUCA method, the worst-case combinations can be confirmed theoretically; thus, FEM calculations for only a few combinations of uncertainties are required, rather than thousands. Compared with the widely adopted design of experiments based uncertain combining methods, the worst-case cogging torque obtained from the WUCA is higher. FEM verification of different pole/slot configurations revealed that the WUCA method was a general and effective method for quickly estimating the worst-case cogging torque under manufacturing uncertainties.

In this paper, a new modeling approach is proposed to investigate cogging torque and the corresponding reduction techniques of flux-switching permanent magnet (FSPM) machines. Firstly, based on the superposition of each single rotor tooth, an analytical expression of cogging torque in FSPM machines is derived and confirmed by finite element analysis (FEA). Then, three feasible techniques, i.e., successively shifting rotor teeth, alternately shifting rotor teeth, and stepped skewing rotor blocks, are proposed for cogging torque minimization of FSPM machines. Correspondingly, generally analytical expressions of these three methods are deduced, through which the analytically optimal shifting angles can be determined. Besides, the cogging torque harmonics are analyzed by both analytical expressions and FEA, and then, the multi-dimensional techniques, namely three rotor-based reduction methods combined with optimal stator tooth width, are introduced and studied to further suppress cogging torque. Finally, prototyped machines are manufactured and tested, and the corresponding experiments verify the effectiveness of the reduction methods.

In this article, a fault-tolerant model predictive current control method is proposed to improve the fault-tolerant ability of a five-phase permanent synchronous magnet motor drive under single and multiple open-circuit faults operations. On the principle of the optimal current control, general reference currents are derived to suppress torque ripples. To obtain the reference currents, a Fast Fourier Transformation-based current estimation model is established. The torque ripple can be reduced by modifying the reference currents in the d3-q3 axis transformed from the estimation model. Finally, experimental results validate the effectiveness of the developed fault-tolerant control strategy and the robustness against operating points and motor parameter mismatches.