What makes wind turbines turn when there is absolutely no wind?

Question

I have heard that turbines must not remain stopped for too long as they can seize up so they actually take electricity from the grid to turn to prevent this. I'd like to know if this is true.

Answer 1

They may be fitted with a 'Turning Gear' which, through a small motor and gear system, powered by the grid, put the Turbine on 'Slow Roll' which maintains the lubrication system.

Answer 2

actually there is some inertia in the turning blade sbecause of their huge weight....

Answer 3

A large steam turbine is fitted with barring gear this is used to turn the whole turbine alternator assembly. The purpose is to stop the shafts self weight sagging. If the barring gear fail hand barring is carried out at around half a turn every 8 hours.

To give an idea of size the alternator rotor alone will weight up to 37 tons

I work on gas turbines up to approx 7 mw output. Barring gear is not fitted to this size and type of generator.

I would think on a wind turbine this equipment would not be necessary.

Answer 4

Exactly! They're useless - too much wind and they don't work, too little wind and they don't work. What's wrong with hydropower?

Answer 5

Most wind turbines use electricity to start & overcome the initial resistance - but there's no problem with them being stationary for any length of time, some of ours locally will be stopped for a week or more if it's dead calm.

Answer 6

it would be possible i suppose, but it is so rare. these things can gather even the slightest breeze.

Answer 7

You're question refers to synchronous machines. This is not the easiest concept to explain here and would take some research on your part.

As far as I'm aware basically all wind turbines designed to supply electricity to a grid are designed using a synchronous machine generator to convert the rotational energy produced by the wind on the fins into electrical energy.

Synchronous generators work by spinning at constant speeds and what happens when there is a lack of wind, the generator will actually TAKE electricity FROM the grid to supply the energy required to keep the wind turbine spinning, rather than letting it stop. This is to do with 3-phase AC electricity and magnetic forces. The same actually begins to happen if the wind begins to spin the turbine too quickly, power is provided by the grid to slow down the turbine.

It may sound daft, but theres a good reason for it (to do with the 60/50Hz frequency that the supply to your home operates at)

My best advice would be to google "Synchronous Machines" and/or find an Power (or Electrical) Engineer who still knows all their stuff from University.

The reason why they would keep the turbines spinning without any wind? You may be correct about them seizing up, but I kind of doubt it unless you live in a place with very low temperatures? Sometimes power stations produce too much electricity as well so this would be a good way to dispense of excess electrical production.

Answer 8

There is always some wind around but they will feather their blades if the wind reaches 70mph