The Switch, manufacturer of permanent magnet generators and full-power converters, recently released a technology paper addressing the ongoing industry debate on drivetrain technology selection. With this paper, the Finnish manufacturer tackles the performance misconceptions still surrounding the main two drivetrain technologies that currently dominate the wind energy industry and explains why the permanent magnet generator (PMG) with a full-power converter (FPC) will emerge as the clear drivetrain technology of choice for modern wind turbines.
“In the wind power industry, the debate on which generator and converter option makes for the best modern wind turbine drivetrain is still raging,” says Jukka-Pekka Mäkinen, The Switch CEO. “Numerous technology experts and industry commentators promote the use of the double-fed induction generator technology, while expressing doubts about the advantages of the PMG approach. In this paper, we aim to set the record straight and explain why PMG with a FPC is by far the best technology, regardless of which key decision-making criteria you use.”
“PMG-FPC drivetrains work out to be a cheaper, more cost-effective option over the total life cycle of the turbine,” he continues. “Moreover, PMG-FPC simplicity leads to superior reliability and higher availability. Many turbine manufacturers still rely on outdated generator technology choices. For those businesses choosing to adopt PMG-FPC drivetrain technology, accepting a steep adaptation curve in the short term will enable them to reap the benefits of superior AEP in the medium and long term.”
Filed Under: Generators, News
George Fleming says
Switch seems to believe that they have developed the ultimate wind turbine power train. They do appear to have better technology than most, but this does not mean that they have the best possible.
Switch requires power electronics, but the technology exists to eliminate these expensive, unreliable and inefficient devices. DeWind has been using it for years. Any system that requires power electronics, full or partial, is obsolete.
Switch requires permanent magnets, but there may be good reasons to avoid them. Two of them are the high cost and the uncertain availability of rare earth elements. Their report naturally dismisses these problems, but it is impossible to know whether they can be dismissed.
More important, permanent magnets may not retain their strength. Here is an interesting statement about that:
‘Wear’ is a somewhat misleading term. Permanent magnets gradually decrease in strength, but this has very little to do with usage. The “life” of a permanent magnet depends on many factors. Naturally occurring forces conspire to knock the little domains out of alignment. But this is normally a very slow process. Temperature is a major player in this process. The higher the temperature, the faster this process will occur. Extreme heat [surpassing the curie point] will immediately randomize the domains. A sharp blow can also knock domains out of alignments, as can other nearby magnetic or electrical fields. Radiation can also knock domains out of alignment. But again, under normal conditions, neither your fridge or you will live long enough to watch the little fellow fall to the floor in exhaustion.
Read more: http://www.physicsforums.com
Switch does not discuss weakening in their report, but they mention the possibility of reversed polarity, and do not claim that this cannot happen with their magnets. They also dismiss the objection that electrical losses with these magnets begin to rise at 176F. (They used the temperature scale of the inferior metric system.) Does it? Someone reading this may know and take the time to comment.
Switch also developed the Fusion Drive. This is also going in the wrong direction, if they intend to mount it in the nacelle. The best place for the generator and gearbox is at ground level, or sea level, but no wind turbine company has yet realized this fact.
The report says: ”
PMGs require the use of NdFeB magnets, which are sensitive to corrosion and heat. For this reason, some industry commentators claim that electrical losses could climb rapidly due to excessive heat. They also wrongly assume that there is a risk of reversed polarity or permanently losing magnetic field strength.