Influence of the electrical steel grade on the performance of the direct-drive permanent magnet machine for wind energy generation

The performance of a variable speed, direct-drive synchronous generator wind turbine concept is compared for two grades of electric steel applied for the generator stator core lamination. A ring type, radial flux permanent magnet synchronous generator (PMSG) is modelled. For a fixed mechanical power input, the geometry of the PMSG is optimized for each material to maximize the annual energy yield. The energy yield is calculated based on the power curve of the generator and the probability density function of the wind speed. This function is approximated by the Weibull distribution for a site with average wind speed of 7 m/s. The annual efficiency differs more than 2% between the two optimized generators, which use different grades of material.