Permanent Magnet Vernier Generator with Surface Ferrite Magnets for a Direct-Drive Wind Generator

Direct-drive wind generators are becoming increasingly popular due to the absence of gearboxes, which leads to various advantages such as noiseless operation, long term reliability and lower frequency of maintenance. Usually, permanent magnet synchronous generators (PMSG) are suitable for direct-drive wind energy conversion systems due to their high efficiency and power factor. However, they have more number of poles, since the wind turbine blade speeds are generally low. Hence, permanent magnet vernier generators (PMVG), which have inherent magnetic gearing effect, low-speed high-torque capability and high torque-to-weight ratio are becoming popular for direct-drive wind generators. Various PMVG designs are proposed till date based on the stator or rotor geometry, winding arrangement and placement of magnets. This article aims to design an outer rotor surface-mounted PMVG with ferrite magnets. Further, the 2-D FEM analysis of the proposed generator is carried-out and the results are presented.