Eddy Brake in Windmill - Why are disc brakes preferred?

JohnInTX

Joined Jun 26, 2012
3,986
I'm guessing that it's because an eddy brake won't work at 0 RPM and the blades need to be lockable for maintenance. As long as you have to have a secondary mechanical brake, why not just feather the blades and set the brake?
Just speculation.
 

oz93666

Joined Sep 7, 2010
737
A big part of the cost in a commercial wind-turbine is the cost of the tower ... this has to be strong enough to with stand the push from the wind transmitted through the blades ...
The amount of push on the tower is related to the power you take out , as wind speeds increase power extracted must be limited or the tower would destruct ... eddy breaking is also extracting power , the structure does not care if you are extracting power from the generator , or eddy breaking it will all result in push on the tower ... so in high wind speed push on tower is reduced by changing angle of blades , this will limit power generated and the push .... Disc breaks are very cheap , used for accurate control of speed ...and holding the thing still for maintenance (which eddy breaks can't do)

Wind turbines are a thing of the past , falling solar panel price has pushed them out of the market , vested interests in the wind industry, politicians and import taxes on panels are distorting the economics.

 
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Janis59

Joined Aug 21, 2017
1,057
My understanding is that electric power at high winds may overload the turbine 10-fold or even 100-fold (power=~speed ^3). That is the basic reason why it must be stopped at high winds, not a centrifugal forces decompositing a blade at few3 hundreds of meters per second, what happens just being the second phase when electrically is not possible to slow it down. So, to avoid the last, the blade must be stopped. But to stop it electrically demands so heavy (and expensive) alternator that it is impossible, whilst disc brake is sth small enough and trustworthy. By the way, small turbines may be not braked, but just steered out of the wind by means of slopy tail, still giving a full power capability for turbine.
Generally, imagine the 10 tonn blade hitting Your house with speed of 100 or even larger speed (tip speed is about so in under-abrasive regime in normal wind and far over at high winds) - and You`ll run away without of delay. So, the brakes must be maximum trustworthy.
 

Janis59

Joined Aug 21, 2017
1,057
RE: ""Wind turbines are a thing of the past""
Still yet propaganded by greens and still financed by local authorities, BUT the elementary analysis shows out that it gives a "no cost" electricity when it is NOT needed and nevar giving electricity when it IS needed. Thus the "dirty" infrastructure of fossil fuels anyway must be used unavoidable, but as it is impossible to switch it on/off just like a home light, it demands a day or even days (except a hydro which can) then in such infrastructure wind energy is without of any use. My daughter is living next to such 50 mill farm at Germany, and rarely she sees are turning one or two of them even in good winds. Most of them stands 350 days annually. They have nowhere to put this "cheap" energy, thus doubling the kilowatt price and giving NOTHING good even to environment except the subsidization from government to it owners.
 

atferrari

Joined Jan 6, 2004
3,787
From all what I learnt (?!) in this last 10 years discharging vessels with windmill components of several manufacturers, brakes are destined to lock the system in case of emergency or for maintenance. I could be wrong but to regulate the speed thus the output frequency, the (blade's) pitch control is used. That is why, in really strong wind, I have never seen any windmill turning.
 
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