A new hybrid method for reducing cogging torque in the AFPM wind generator

ABSTRACT

Reducing the cogging torque in the axial flux permanent magnet (AFPM) generators is an important study area. Especially, AFPM generators with open slotted and rectangular-shaped poles have high cogging torque and high total harmonic distortion (THD). Generators used in wind turbines require minimal mechanical vibration and a smooth sinusoidal wave. In this study, a new hybrid method is proposed to reduce the cogging torque and increase electrical performance. The proposed method involves combining two techniques to reduce cogging torque, including magnet placement angle and magnet grouping technique. In the proposed hybrid method, the electrical performance of the AFPM generator has improved for the minimum cogging torque. This proposed new method is cost-effective and easy to apply. 3D finite element method (FEM) and experimental verifications were performed for the accuracy of the proposed method. When the results are examined, cogging torque was improved by at least 80% with the new hybrid method. However, the electrical performance has been improved for 10% power loss, and the total harmonic distortion (THD) has been reduced to less than 3%.

KEYWORDS:

• Wind turbine
• axial flux generator
• permanent magnet
• cogging torque
• energy quality

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Nomenclature

AFPM	=	Axial flux permanent magnet
THD	=	Total harmonic distortion
FEA	=	Finite element analysis
3D	=	Three dimensional
PM	=	Permanent magnet
MMF	=	Magneto motor force
d-q	=	Direct-quadrature
DLMSS	=	Dual-layer magnet step skewed
DOE	=	The experiment method’s design
Tc	=	Cogging torque
ϕg	=	The air gap magnetic flux
θ	=	The angular position of the rotor
R	=	The reluctance of the air
kc	=	An integer
Pu	=	Per unit
FEM	=	Finite element method

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Notes on contributors

Engin Hüner

Engin Hüner is an assistant professor in the Department of Energy Systems Engineering at the Kırklareli University (Turkey). He completed a bachelor’s, master and Ph.D. degree in Electrical Education of Abant İzzet Baysal University, Electronical Engineering of Gebze High Technology Institute, and Electrical Education of Marmara University, respectively. His research areas mainly focus on electrical machines and renewable energy systems.

Aykan Mutlu

Aykan Mutlu completed a bachelor’s and master's degree in Electrical Engineering, and Energy Systems Engineering at the Kırklareli University (Turkey). His research areas focus on electrical machines and renewable energy.