The aim of this paper is to design, analyze and optimize the “Multi-Stack Slotless Axial Flux Switching Permanent Magnet Machine”. In the design process, mathematical models are implemented, and the Finite Element Method (FEM) is performed to analyze the machine performances. The paper aims to minimize the occurrence of cogging torque and torque ripple in the multi-stack slotless stator AFPM machine. As a consequence, it reduces the vibrations in the machine and increases its life span. Multi-stack slotless stator AFPM machine with a right-angled trapezoid-shaped PM is proposed and comparison is done with conventional shape AFPM machine. In order to examine the performance of multi-stack slotless stator AFPM machine Finite Element Analysis (FEA) is used. To further enhance the characteristics of the designed machine with the proposed right-angled PM shape, optimization is done by considering inner and outer pole pitch as the design variables. In optimization process, krigging method assigned with Latin Hyper-cube Sampling and a genetic algorithm (GA) is performed due to suitability with non-linear data. Then, finite element analysis by JMAG-Designer is performed to verify the results. It is determined that optimized model has achieved 65% reduction in torque ripples as compared with the conventional design. Hence, this work attempts to optimize the performance of the AFPM machine.

In this paper, a hexagonal magnet shape is proposed to have an arc profile capable of reducing torque ripples resulting from cogging torque in a single-sided axial flux permanent magnet (AFPM) machine. The arc-shaped permanent magnet increases the air-gap length effectively and makes the flux of the air-gap more sinusoidal, which decreases air-gap flux density and hence causes a reduction in cogging torque. Cogging torque is the basic source of vibration, along with the noise in PM machines, since it is the main cause of torque ripples. Cogging torque is independent of the load current and is proportional to the air-gap flux and the reluctance variation. Three-dimensional finite element analysis (FEA) is used in the JMAG-Designer to analyze the performance of the conventional and proposed hexagonal-shaped PM AFPM machines. The proposed shape is designed to reduce cogging torque, and the voltage remains the same as compared to the conventional hexagonal-shaped PM machine. Further, optimization is performed by utilizing an asymmetric overhang. Latin hypercube sampling (LHS) is used to create samples, the kriging method is applied to approximate the model, and a genetic algorithm is applied to obtain the optimum parameters of the machine.

In this paper, a novel dual port counter rotating dual rotor wound field flux switching generator (DPCRDR-WFFSG) is proposed for direct drive counter rotating wind power generation. Mechanism of gearless and brushless counter rotating operation of DPCRDR-WFFSG is discussed and simplified formulation is opted for possible combination of the rotor poles number $(N_r)$ . In proposed DPCRDR-WFFSG, dual electrical ports are formed of non-overlapped armature winding having shared toroidal field excitation winding whereas inner and outer rotors act as inner and outer port. These inner and outer port are thoroughly investigated for electromagnetic performance to search out optimum rotor poles combination. The rotor poles combinations are examined under uniform and non-uniform poles and comparatively studied. Based on simplified formulation, various combinations of the rotor pole numbers are searched out and found that under uniform poles operation, $N_r= 10$ and $N_r = 14$ offers comparatively better electromagnetic performance whereas in case of non-uniform rotor poles $N_r = 10/14$ further improves electromagnetic performance. Furthermore, analysis evident that in comparison with the inner port, outer port shows dominant contribution in electromagnetic performance whereas, in comparison with uniform rotor poles, the new approach of adopting non-uniform rotor poles improve electromagnetic performance. It is worth noting that non-uniform rotor poles in inner ports improves efficiency and power factor whereas in outer port, average torque and output power are enhanced. Finally, validity of uniform and non-uniform rotor poles design approach for DPCRDR-WFFSG is verified with four prototype that validated finite element analysis.

Permanent magnet vernier machines (PMVMs) are becoming progressively attentive because of their high efficiency and high torque density and can thus be utilized for direct-drive applications such as wind power and electric vehicles etc. This paper presents performance improvement of multi-rotor axial flux vernier permanent magnet (MR-AFVPM) machine with a proposed two-stage parallelogram-shaped PM. The proposed shaped PM reduces the cogging torque and torque ripples due to its skew effect. Furthermore, it also presents a comparative analysis of the conventional and proposed shape PM. Then 3D finite element analysis (FEA) is used for comparative analysis. Genetic algorithm (GA) associated with kriging method based on LHS is introduced and is used to optimize the proposed shaped PM for further performance improvement in terms of cogging torque, back EMFs, torque ripples, VTHD, output torque, flux density distributions, power factor and output power of the analyzed machines which are validated by 3D-FEA.

To overcome drastic increase in rare-earth permanent magnet cost, avoid the requirements of brushes, slip rings, and eliminate gear-box mechanism, a novel magnet-less dual electrical and dual mechanical port wound field-excited flux switching generator (DEDMP-WFEFSG) for direct-drive counter rotating wind turbine (D ² CRWT) application is proposed in this paper. The proposed DEDMP-WFEFSG encompasses a stator with dual non-overlapped armature and toroidal field excitation windings; thus, offers reduced overhang and makes the design compact. To ease the design process, lumped parametric magnetic circuit model (LPMCM) for one magnetic pole is formulated. To evaluate the LPMCM design, finite element analysis (FEA) study is undertaken in co-rotation and counter rotation with focus on power distribution between the inner and outer ports. From detailed analysis, it is evident that in comparison with the inner port, the outer port machine offers better average torque, power factor and efficiency. Compared with co-rotation, counter rotation shows improved electromagnetic performance. Finally, to validate the LPMCM and FEA based simulation, a prototype is developed and tested with satisfactory results.

To eliminate slip rings, brushes, and terminate gear-box mechanism, ferrite permanent magnet (PM) based counter rotating dual rotor PM flux switching generator (CRDRPMFSG) for direct drive counter rotating wind turbine (D ² CRWT) application is proposed in this article. Initially, the mechanism of gearless and brushless counter rotating wind power generation is discussed, and a simplified formulation is opted for the slot/pole combinations. The proposed CRDRPMFSG encapsulate inner and outer machines with circumferentially magnetized PM enclosed by non-overlapped armature windings; thus, offering reduced overhang with compact design. However, co-axially linking the inner and outer machines through a shared stator yoke results in serious issues of magnetic coupling due to dual air-gap fields. To this end, eight topologies with various slot/pole combinations are comprehensively investigated using finite element analysis (FEA) for magnetic coupling effects and its influence on electromagnetic performance. From the analysis, it is shown that magnetic coupling level influence electromagnetic performance i.e., average torque, ripple rate, power factor, efficiency, losses, and output power. Moreover, it is noted that coupling level can be reduced by adopting same stator teeth in inner and outer machines or same stator teeth with different rotor poles. Finally, the predicted FEA calculations are verified experimentally with four benchmarked CRDRPMFSG prototypes.