Scaling of Pseudo Direct Drives for Wind Turbine Application

A Rare-Earth Free Magnetically Geared Generator for Direct-Drive Wind Turbines

“…This phenomenon makes Vernier machines a suitable option for low-speed high-torque applications. Various topologies are proposed for permanent-magnet Vernier (PMV) machine [16][17][18][19]. In [16], a novel dual PM Vernier machine is proposed in which PMs are placed on both stator and rotor sides to increase fundamental value of the air gap flux density.…”

“…Although both the power factor and the torque density are improved in that topology with respect to single stator option, complex mechanical structure makes it less reliable. In [18], a magnetically geared generator called Pseudo Direct Drive (PDD) is proposed for direct drive wind turbine applications. This generator promises a high torque density and reasonable power factor; however, it is composed of two rotating parts, which make the structure complex and less robust to be used as an offshore wind turbine generator.…”

“…Magnetically geared PMV machines require several times more PM compared to conventional DDPM generators, which makes them less attractive. For instance, the topology presented in [18] requires excessive mass of PM which is about 25% of the generator active materials mass. Using field winding instead of PMs may be considered as a solution to reduce the capital cost and make Vernier machines economically feasible for large scale wind turbines.…”

“…Using field winding instead of PMs may be considered as a solution to reduce the capital cost and make Vernier machines economically feasible for large scale wind turbines. For that purpose, the proposed generator in [18] is revised in [20] and PMs in high speed rotor are replaced with field windings to reduce PM usage.…”