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Q & A: Why gearboxes in wind turbines

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Most recent answer: 05/26/2012
Q:
Hi, I need to find out why a gearbox is needed between the blades and the generator in a wind turbine. Thanks :)
- Sophie Patient (age 14)
Christchurch, Redwood, New Zealand
A:
The general reason for using gears is that different parts need to run at different speeds for efficiency. In order for a compact electrical generator to work well, some parts have to move fairly fast, since the voltages generated depend on how fast some magnetic fields are changing. The turbine blades themselves, however, can't turn very fast because they wouldn't be able to take the centrifugal strain. So a gear box is needed to step up the slow turbine motion rotations to the faster generator rotations. One alternative to using gearboxes, however, is to use a larger generator with permanent magnets ().

The precise amount of gearing needed depends on various factors including the wind speed, so in most turbines the gears can be shifted, like those in a car. I've heard there are new designs which use fixed mechanical gears and instead electrically switch the connections of some of the coils in the generator, changing its optimal operating speed. Electrical switches are faster and easier to control than are mechanical gear shifters, so this should improve turbine performance.

Mike W.

(published on 05/26/2012)

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