Comparative design of radial and transverse flux PM generators for direct-drive wind turbines

The aim of this paper is to assess the radial flux permanent magnet (RFPM) and transverse flux permanent magnet (TFPM) generators for large direct-drive wind turbines. For the assessment, the electromagnetic design of RFPM and TFPM generators is done. The analytical design result of a TFPM generator is compared with the experimental result. A RFPM machine concept and four different TFPM machine concepts are designed electromagnetically for 5 MW direct-drive wind turbines. These machines are assessed with criteria such as the cost, the mass, the copper loss, the power/mass ratio, the power/cost ratio, the cost/mass ratio and the mass/torque ratio.