Phenomenon of magnetic force in permanent magnet wind turbine generators

This study presents the investigation on the magnetic force phenomenon in permanent magnet (PM) wind turbine generators. Owing to the presence of PMs, the inherent and ever-existing magnetic force between the stator and rotor becomes one of the most critical phenomena in these generators. Whether it is during the assembly process throughout the manufacturing stages or when the generator is in operation, it is essential to calculate these forces and their distributions. The unbalanced resultant force due to the manufacturing tolerances, rotor eccentricity or bearing displacement under high wind loads, can be calculated with the force distribution function which is derived from the air gap flux density using 2D magneto-static finite element analysis (FEA). The obtained results show the good agreement with the figures based on the time-stepping FE approach. The effective force distribution derived can be sufficiently employed with 3D FEA to study the overall mechanical integrity of the wind generator design.