Wind power electrical drives for permanent magnet generators — Development in Finland

The use of permanent magnets offers freedom in machine design and the highest possible efficiencies for wind power machines. Although full power converters must be used with permanent magnet machines, these converters make it possible to fulfill even the strictest grid codes. If appropriate care is taken in selecting the exact magnetic material composition, Neodymium-Iron-Boron magnets are compatible with long term generator use. However, rare earth material prices have been so volatile lately that highpower applications using lower strength ferrite magnet materials are being studied. For wind power applications, the three basic types of PM generator include direct-drive generators (10-20 min^-1), medium-speed generators (100-300 min^-1), and high-speed generators (1000-2000 min^-1). Finnish companies such as Neorem Magnets, ABB, and The Switch have been very active in the development of permanent magnet technology for wind power. Moreover, Finnish wind turbine manufacturers operating today use the most modern PM technologies in their products.