Comparison between rare-earth and ferrite permanent magnet flux-switching generators for gearless wind turbines

Vladimir Prakht,Vladimir Dmitrievskii,Vadim Kazakbaev,Mohamed N Ibrahim

doi:10.1016/j.egyr.2020.11.020

Vladimir Prakht, Vladimir Dmitrievskii + Show 2 more

Open Access

https://doi.org/10.1016/j.egyr.2020.11.020

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Journal: Energy Reports	Publication Date: Dec 1, 2020
Citations: 15	License type: cc-by

Affiliation: Ural Federal University, Ghent University

Abstract

Flux switching generators with permanent magnets (PMs) on the stator is a good alternative to traditional synchronous generators for gearless wind turbines. This paper is dedicated to the comparison of the 3-phase rare-earth and ferrite PM flux switching generators considered in gearless wind generator application (332 rpm, 1784 W). The machines are designed and optimized using the Nelder–Mead algorithm coupled with 2D FEM model. The objective function is built taking into account the following objectives: the average efficiency of the generators over the wind turbine profile, the required power of the AC–DC converter, the quantity of the magnets and the torque ripple. It is found that the ferrite PM flux switching generator can be an attractive alternative to the rare-earth one. The averaged efficiency of the generator with ferrite PM is higher by 4.1% than that of the rare-earth one. The active power of the ferrite generator is also higher in a wide range of powers. Although the mass of the ferrite PM generator is 2.4 times higher, the costs of the generators are approximately similar since the rare-earth magnets are much more expensive than ferrite ones.

Highlights

Synchronous machines (SM) with permanent magnets on the rotor have been widely used in gearless generators of low-power wind turbines
The mass of the flux switching generators (FSG) with ferrite magnets is 2.4 higher than that of the FSG with rare-earth magnets, the costs of the generators are approximately similar since the rare-earth magnets are much more expensive than ferrite magnets
This paper has presented the comparison between two flux switching machines based on rare-earth and ferrite magnets for a direct-driven wind turbine

Summary

Introduction

Synchronous machines (SM) with permanent magnets on the rotor have been widely used in gearless generators of low-power wind turbines. In paper [10], optimized designs of rare-earth and ferrite FSGs are compared in geared wind turbine applications. It was reported that the specific torque and active material cost of the rare-earth FSG is 1.63 and 1.65 times higher than those of the ferrite FSG respectively. The efficiency of the rare-earth and ferrite FSGs are 94.01% and 95.18% respectively Both the FSGs under analysis have a quite low power factor of 0.79 and high torque ripple. This paper compares 3-phase rare-earth and ferrite FSGs in gearless wind generator application (332 rpm, 1784 W). The objective function is built taking into account the following objectives: the average efficiency of the generators over the wind turbine profile, the required power of the AC–DC converter, the quantity of the magnets and torque ripple. Optimization is carried out using substituting two-mode load profile that considerably reduces computational time

Geometry of the flux switching generator

Optimization of the flux switching generator

Results and discussions

Conclusions