Multi‐objective design and prototyping of a low cogging torque axial‐flux PM generator with segmented stator for small‐scale direct‐drive wind turbines

Abstract

The multi-objective design of an axial-flux permanent magnet (PM) generator with the yokeless and segmented armature is done, for use in the small-scale direct-drive wind turbines. Using the multi-objective genetic algorithm technique, an optimisation process is performed for maximising the efficiency and minimising the cost, size, and mass of active materials, considering the practical constraints of the wind generator. The Pareto optimal fronts are used to find the best solutions. Also, a comparative study is performed to determine the most appropriate configuration among 12 configurations with the different combinations of poles and stator segments. Then, the selected optimal configuration is analysed using the three-dimensional (3D) finite element analysis (FEA). The inherent cogging torque of the PM wind generator affects the cut-in speed and start-up of the turbine. Thus, to improve the turbine performance, especially at low starting speeds, the generator cogging torque should be reduced to an acceptable level. In this study, using a new and practical approach, the peak-to-peak value of the cogging torque is reduced largely (81.4%), without notable reduction in the generator loadability. A prototype of the designed generator is fabricated and tested. The experimental results show good agreement with the 3D FEA simulation results.

Electromagnetic design and performance analysis of a two‐phase AFPM BLDC motor for the only‐pull drive technique

“…The source of torque ripples in PM BLDC motors can be due to motor design and motor control [2,[15][16][17][18]. In this work, the cogging torque due to the open slot structure in the design, nontrapezoidal back-EMF of the RFPM motor, and single-phase current commutation in the control is responsible for the torque ripples.…”

Voltage regulation Rate and THD optimization analysis of coreless axial flux PM synchronous generator for wind power generation

“…An axial flux permanent magnet synchronous motor has the advantages of small axial dimension, compact structure, high efficiency, and high power density, so it is widely used in wind power generation , electric vehicles , transportation and so on. However, permanent magnet generators also have their own shortcomings.…”

“…By changing the pole‐arc offset distance, the corresponding air‐gap flux density and phase voltage are obtained, the THD and efficiency of the generator are analyzed to obtain the best pole‐arc offset distance . Multi‐objective optimization method is used to optimize the efficiency, size, cost, and weight of the generator, and a method of reducing cogging torque by segmented magnets is proposed, which ensures that the generator loadability is not affected too much . Based on the finite element method (FEM) of two‐dimensional numerical analysis, the basic design and characteristic analysis of a small 3 kW wind turbine are carried out.…”

Wind Micro-Turbine Networks for Urban Areas: Optimal Design and Power Scalability of Permanent Magnet Generators

“…Plenty of PM synchronous generators, whether axial flux or radial flux machines, have been presented in the literature in the last decades [14][15][16][17]. Moreover, the research is focused on non-conventional configurations that were aimed at improving the overall performance or reducing the manufacturing issues.…”

“…The work reported in [16] presents a transverse flux PM disk generator, whose main feature is the adoption of modular H-shaped stator cores made by two T-shaped cores plus a permanent magnet in order to simplify the assembling process. In [17], the design of an axial-flux PM generator with a double rotor and one yokeless segmented stator is performed by means of a multi-objective optimization aimed at maximizing the efficiency and reducing the cost of active materials. A comprehensive methodology for the design of a radial flux iron-less PM machines is presented in [14]: three-dimensional FEA is used and the simulations are validated after experimental tests; the adopted topology has solenoid-shaped coils and a simple mechanical design so to guarantee ease of maintenance.…”