Ring-shaped transverse flux PM generator for large direct-drive wind turbines

A ring-shaped transverse flux permanent magnet (TFPM) generator with double-sided axial flux configuration is proposed in this paper. The ring-shaped TFPM generator does not use a shaft and arms to transfer the torque and to support both the rotor and the stator. The active part of the proposed generator consists of multiple-segment structure. This new generator configuration can remarkably reduce the mass, and can make the construction easy in manufacturing and handling. Analytical design model is developed for the TFPM generator. The analytical model is verified by the experimental analysis of the downscaled generator. The design results of 5 MW ring-shaped TFPM generators are compared with two different generators, namely a conventional radial flux PM generator and a single-sided air gap TFPM generator.