Direct-drive generators to be used in off-shore wind farms are very large low-speed electric machines which pose remarkable design and manufacturing challenges. Demand forecasts for this kind of machines are urging manufacturers to work out design and technological solutions that can facilitate series production at competitive costs. This paper presents the development of an interior-permanent magnet generator design and technology aimed at reducing series manufacturing costs while preserving high performance levels. The proposed solutions are validated through the construction and testing of a 780 kVA generator prototype conceived for easy scalability to higher power ratings (up to around 2.5 MVA) by core length increase.
