Microwind brake

[Enrique Munoz]

Hi everyone,

Longtime lurker, first time poster :)

I'm working on supplementing my solar system in Patagonia with a 500W wind turbine. There are almost consistent 15 mph+ winds down there and our needs are pretty modest, so I think that it will be a good addition.

The only area that I'm struggling with is figuring out what the best way to brake it when there's a windstorm or we're not in town (which is actually most of the year). The easiest way seems to be to short the three output wires, but I've hard that that can make the stator wiring melt. Others recommend adding a resistor between each wire and the short, which I guess makes sense.

Any thoughts or ideas?

Best,
Enrique

[Dave Lahar]

Hi E,

There was a recent post on OP on this topic that you might find of interest: https://www.fieldlines.com/index.php/topic,149998.0.html?PHPSESSID=9c49390a5d77def42c56 cc645140516f

If you turbine has is 3-phase AC output, as many do, shorting the windings is one method of braking.

Another method, which I prefer is to use a furling tail. This can be used for speed control, but with a line down the tower and small hand-winch can allow you to safely, softly manually furl the tail (bringing the blades parallel with the tail) to slow and or stop the thing. I posted a story on ours on Hugh Piggott's site this summer (aka kitestrings).

[Rob Beckers]

Welcome to the forum Enrique!

Shorting the windings works well if you have a good alternator, that generates large forces when shorted (when you try to turn it). The risk of shorting the windings is if the alternator can't hold the turbine, and it spins up at high wind speeds despite the shorted windings. If that happens very large currents will flow through the 3 phases and burn out the stator. Using resistors doesn't really help with that, in fact it makes it more likely that the turbine will spin up again at some wind speed. People use resistors to be able to stop the turbine while it's spinning; abruptly shorting the 3 phases is much like throwing a stick into a bicycle wheel while you're moving, it's a very harsh way to stop a turbine, and the resistors help soften that a bit. They're not great for keeping the rotor stopped though.

I'm with Dave, that if you an furl the turbine, or tilt the tower down and tie up the rotor, those are much better ways to make sure nothing bad happens while you're away.

By the way, we've sold some Primus AIR-X Marine turbines to a customer that runs them up north to power measurement equipment (and weather over there is very extreme). These are around 300 Watt rated output. Primus is not the greatest of turbines, but they are relatively cheap, decently built, and spare parts are easily available. They also will stop themselves in high winds (controller is build into the nacelle). One of those could be a good option.

-RoB-