Design of direct-drive wind turbine electrical generator structures using topology optimization techniques

Reducing the structural mass of low speed multi-MW electrical machines for renewable energy purposes have become an important object of study as with the drop in mass a substantial decrease in the machine capital cost can be achieved. Direct-drive wind turbine electrical generators need very robust and heavy supporting structures able to cope with the demanding requirements imposed by the environment and the forces and moments transmitted by the wind turbine rotor in order to maintain the air-gap clearance open and stable. It is estimated that at least 2/3 of the total machine mass corresponds to the supporting structure. The main aim of this investigation is to minimize the structural mass of a 3 MW direct-drive wind turbine permanent magnet electrical generator, which dimensions have been previously optimized, making use of topology optimization techniques. Easy to manufacture structures made of cast iron capable of complying with the requirements were generated for both rotor and stator.