Wind Generator Brakes

LostDog88

New Member
Do all wind turbines have brakes? What controls them? The controller I am guessing.

Can someone elaborate please?
 

svetz

Works in theory! Practice? That's something else
Staff member
Moderator
Don't know much other than they all need some way to keep the top RPM from being exceeded to avoid damage. Not sure that means brakes, prop pitch change or turning sideways might do. Hopefully someone more knowledgeable will post.
 

LostDog88

New Member
I keep seeing things about dump loads. I wonder if some have brakes and some just dump the unnecessary power created?

I know that there is a discussion about how wind is (not) worth the time, but I think it is here in the windy NW.
 

rhino

Solar Enthusiast
The problem with "small" wind turbines is they are a mechanical device that will wear out. Even in cloudy NW it may make more sense to add more panels since you do still generate electricity with them even on cloudy days. I've gone through two 1KW wind turbines. An African Wind Power and a Kestrel e300. The Kestrel looked far superior in quality and workmanship but even then on top of a 100ft tower it failed in less than 3 years. The output of the AWP was 3 phase wild AC and to brake it you could flip a switch by the controller to short the wires. If wind was too strong even that would not stop it so in really windy conditions you'd need some sort of mechanical device to stop it. The Kestrel had 110V DC output which also had a switch to short the 2 DC cables. Doing this makes it very difficult for it to spin because of the magnetic field inside the turbine. The Kestrel would also pitch out of the path of the wind if it started to get too windy. So it was a much safer system than the AWP.
 

rhino

Solar Enthusiast
I currently have no idea what would be a safe reliable wind turbine under the 10KW range. If you happen to find one I'd be interested.
 

LostDog88

New Member
The problem with "small" wind turbines is they are a mechanical device that will wear out. Even in cloudy NW it may make more sense to add more panels since you do still generate electricity with them even on cloudy days. I've gone through two 1KW wind turbines. An African Wind Power and a Kestrel e300. The Kestrel looked far superior in quality and workmanship but even then on top of a 100ft tower it failed in less than 3 years. The output of the AWP was 3 phase wild AC and to brake it you could flip a switch by the controller to short the wires. If wind was too strong even that would not stop it so in really windy conditions you'd need some sort of mechanical device to stop it. The Kestrel had 110V DC output which also had a switch to short the 2 DC cables. Doing this makes it very difficult for it to spin because of the magnetic field inside the turbine. The Kestrel would also pitch out of the path of the wind if it started to get too windy. So it was a much safer system than the AWP.
So this means they all have brakes? Or some means to stop the rotation? Or is it something that must be listed in the "specs?"
 

rhino

Solar Enthusiast
So this means they all have brakes? Or some means to stop the rotation? Or is it something that must be listed in the "specs?"
No, some will pitch out of the wind path which prevents it from spinning too fast but does increase the noise of the turbine significantly when it is doing that.
 

LostDog88

New Member
No, some will pitch out of the wind path which prevents it from spinning too fast but does increase the noise of the turbine significantly when it is doing that.
So....If I want one with a "brake" I will need to get a wind turbine and controller that allows braking?
 

svetz

Works in theory! Practice? That's something else
Staff member
Moderator
I keep seeing things about dump loads. I wonder if some have brakes and some just dump the unnecessary power created?
Dump loads are something else...as I understand it (caveat: repeating what I've heard to the best of my understanding, not an expert).

With solar panels you can just disconnect them if you have too much power. The sun can keep shining down on them and they won't be damaged.

But I believe with wind turbines if you're making too much power you can't just turn it off... doing so would hurt it. Instead, you have to "dump" the excess power somewhere. Possibly a brake can also perform that function, but I don't believe a dump by itself can keep the turbine from spinning itself into pieces (possibly it increases the load which increases the reistance?). Again, not an expert.

...I know that there is a discussion about how wind is (not) worth the time, but I think it is here in the windy NW.
It's summed up here: www.solacity.com/small-wind-turbine-truth/
 

LostDog88

New Member
That article is pretty good.. bottom line, I would avoid spending money on a small wind turbine (<10KW) at all costs.. it is just a waste of money and my experience supports that conclusion.
As per the article:
If you are off-grid you should definitely consider adding a wind turbine. Wind and solar tend to complement each other beautifully; the sunny days tend to be not very windy, while the windy days tend to have little sun.
Exactly why I want to get one.....So...........Not to be rude but the debate on whether wind turbines are worth it or not is in another thread somewhere.

For me. I want one and have questions.

Questions like is there brakes on all windmills? How is it controlled? etc.

Again, not to be rude, but can we keep this on the topic of brakes and not whether YOU think they suck or don't suck?
 

LostDog88

New Member
I currently have no idea what would be a safe reliable wind turbine under the 10KW range. If you happen to find one I'd be interested.
I am looking at several at this point. Most of them on Amazon. I see several 1200 Watt ones but the only MPPT controller I could find is only rated for 600 Watts. :-(
 

wjjones

New Member
I keep seeing things about dump loads. I wonder if some have brakes and some just dump the unnecessary power created?

I know that there is a discussion about how wind is (not) worth the time, but I think it is here in the windy NW.
That's what I am currently trying to figure out too. Dump, and diversion load stuff.
 

wjjones

New Member
Do all wind turbines have brakes? What controls them? The controller I am guessing.

Can someone elaborate please?
Ours is controlled by the charge controller but it's to my understanding it always needs a load to work correctly. I'm still trying to find more info on that myself.
 

LostDog88

New Member
Ours is controlled by the charge controller but it's to my understanding it always needs a load to work correctly. I'm still trying to find more info on that myself.
My understanding is that MPPT will use some sort of shorting across two of the phases to brake the generator. I cannot get anyone to confirm. I can't find data online and even my questions to the manufacturer go unanswered.
Basically what they say is true. Wind turbines are as elusive as the wind.
 

FilterGuy

What, me worry?
I have not installed a wind turbine, but I have installed a hydro turbine. There are similarities but the big difference is that with the hydro, I pretty much know what the most water will be. With a wind turbine it is hard to know what the most wind will be.

Having said that, they both should not be allowed to be 'disconnected'. If the generator is left open circuit, it does not put a resistance on the turbine shaft so it will spin as fast as the wind (or water) can turn it. This is known as freewheeling and in the worst case, the overspeed can destroy the windmill.... Even if the windmill does not tear itself apart, the overspeed is very bad on the bearings. Consequently, you always want an electric load on the turbine. That leads you to the problem of what to do if the batteries are full and the load does not need the power that is being generated...... that is where a dump-load controller comes in. Rather than shut off the excess current it diverts it to a 'dump load'. Sometimes the dump load is just a very high wattage resistor that burns off the energy. (More on that later).

For small wind turbines, they don't have mechanical breaks and depend on the resistance from the load to keep the rotation speed down. (I have always wondered if that is really enough for all conditions, but apparently it is for the small turbines).

Warning: the following is my best understanding.... but it is not based on direct experience.

Apparently the really cheapo controllers out there just short out the wind turbine when it does not need the current....That keeps the current flowing and prevents freewheeling, but from what I have read that is really bad on the generator.

The other thing I have heard about the cheapo wind controllers is that they just drive to a fixed voltage.... the don't really have a charge profile.

The next step up in controllers have a charge profile but they use the dump load to manage the voltage at the batteries.

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If the controller wants to let the voltage go up, it quits dumping to the resistor. If the controller wants to hold the voltage, it sends the current to the resistor. I think the Xantrex C35 works this way.


Stepping up from there... the midnite solar classic has provisions for dump loads and I hear it is considered one of the best for this type of application. From what I have read, the Midnite MPP algorithm works well for finding the optimal Voltage-Vurrent point for the amount of wind the turbine is getting. (Turbines have an MPP curve just like solar panels do)

Some people work out schemes to use the dump load as a water heater or even a space heater. I have not really investigated that a lot, but it seems to me that at some point the water heater could get too hot.....so you then have to divert to a traditional dump load.

BTW: When choosing the rectifier..... they are not all the same. You want to get a full wave rectifier with low energy loss. (I have heard some of the rectifiers being sold for wind turbines are only half phase rectifiers.)
 
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FilterGuy

What, me worry?
This forum does not discuss wind turbines much and (as you have seen) has a bit of a bias against them. I don't have an opinion either way, I have no doubt the are issues with them, but I also see that there could be some nice benefits. If I ever have a place a wind turbine might make sense, I will investigate it and decide then.

So.... I advise you to do some searching on youtube. There are a bunch of folks out their talking about them, and can provide a lot of good information. However you should *always* take everything you hear / read with a little skepticism (Including stuff you read here :) ). A lot of the sites just want you to bite on their click bate or buy through their affiliate links.
 
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