Permanent magnet generators use magnetic force to generate electricity in conjunction with some form of mechanical movement, normally wind power. The primary benefit of a permanent magnet generator is that because there is no need for brushes which improves the reliability of the drive train.
With a permanent magnet generator the number of magnetic poles combined with the rotational speed of the turbine come together to give the frequency of the generator. This means that as the turbine size increases the complications and challenges of using a permanent magnet generator combined with that turbine also increase. Still the improved reliability provided means that this type of generator is continuing to increase in market share.