LF: voltage cut-off circuit for a wind turbine

[fabieville]

I need a circuit schematic that senses when the turbine reaches a certain voltage and then it just either auto-brake the turbine by shortings the output and then release it again after a couple of secs or it send that power to dump load until the voltage has cutdown below the preset voltage.

[gizmo]

Hi Fabieville

What are your electronics skills like? Do you want it simple, or something you can program?

Shorting out the mill isn't a good idea, its better to switch a dump load across the battery bank to drain off the excess power.

Glenn

[fabieville]

I want it simple and i would prefer it had a dump load because i know that shorting out the turbine would maybe cause a problem although i was not talking about shorting out a dc turbine. I was referring to a AC PMA. I need to block an excess of 50volts so whenever the turbine reach close to that voltage then the circuit would send that power to dump load until the voltage drop below the 50volt then it would cut off back the dump load. I am planning to run the wind turbine to a mppt charge controller that can handle up to 50V max. So do you think it will work?

[ghurd]

Shorting an AC PMA is bad too.

"I need to block an excess of 50volts so whenever the turbine reach close to that voltage then the circuit would send that power to dump load until the voltage drop below the 50volt then it would cut off back the dump load".
Lets think about that for a second.
The voltage is above 50V, so the circuit shorts the PMA.
As soon as it is shorted, the voltage is below 50V.
As soon as it is below 50V, the circuit 'un-shorts' the PMA, resulting in over 50V....
Resulting in a classic case of oscillation.

Sounds lile you are looking for a clipper circuit.
If it is for something with low current, like the windblue, could probably use a Zener and 2N3055.
G-

[fabieville]

i have a windblue using but instead of shortings out the turbine couldn't i just activate a dump load when it reaches the 50volt then cut off dump load whenever it drops below 50volt?

And i dont think it would work like a classic oscillation due to the fact that its wind power we are talking about and is not everytime the wind turbine would be operating near 50 volt as it all depends on the wind speed.

Would it be possible for someone to post  a schematic for me as i really  need it as i am planning to buy one of those cheap mppt off ebay that comes with 50v max input to run my windblue but i need a circuit or something to cutoff the voltage from the turbine to the mppt if it goes up too high. I am just trying it on my windblue to see if i could getter a better charge from it by running it through the mppt. So it's basically an experiment as i am not sure what will be the outcome.

[Flux]

Yes the idea could work. Not sure how well a mppt controller ( presumably designed for solar) would work with wind.

The power level would decide on the complexity of the dump load/clipper. If it is a small machine then a fairly simple linear dump would work well enough. If bigger you would probably need to go pwm then you have many issues to contend with unless you use a series choke . A plain resistive chopper could give you lots of unexpected things when chopping the output of a pma ( it may do more boosting of volts than limiting unless you filter it well).

Possibly a solid state relay could bring in a fixed dump load just below the 50v point. It will almost certainly oscillate unless you choose the resistor very carefully but that may not matter but again be very wary of spikes although the mppt controller may have enough input capacitance to filter it out.

For this to work reasonably well you would need the controller to be able to cope in normal winds and just rely on the clipper for the odd occasion. If it is clipping in normal winds then it will probably be worse than not trying the mppt device. I am doubtful anyway that you will see much benefit unless you have some form of mppt converter that can be programmed. I doubt that a tracking solar controller will give sensible results on wind, it's a much more difficult situation.

Flux

[Flux]

You have added some information since my reply. The power level of the windblue will be low so a clipper using a few transistors and some resistance would make a satisfactory linear clipper. Can't really offer you a circuit but as ghurd said some power transistors with a zener feeding the base and a resistor in the emitter circuit would probably work fine. The 2N3055 is a bit close on the voltage limit but even that should work as it should clamp hard and is ok to 60v Choose the resistor to handle the full power and keep a bit below 50v, that way the dissipation in the power transistors will be fairly modest, just use a good heat sink.

Be interesting to see how well it works, I suspect a manually controlled buck converter may work better than a solar mppt controller if you can get something cheaply.

Flux

[klsmurf]

Sorry if this is somewhat of a hijack, but I saw this trolling fleebay yesterday:http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=360357686507&ssPageName=STRK:MEWAX:IT. I have an Ametek 40 and thought something like this controller could possibly be useful. I sent the seller a couple questions, but haven't heard anything back. I see this seller also sells those stackable, plug-in grid tie inverters, so I'm leary to begin with.   Kevin

[fabieville]

with the manually control buck converter i would have to keep on adjusting it to suit the wind turbine?

[ghurd]

but I saw this trolling fleebay yesterday...

If it works like they claim it works, I would not use it at all!

And its interesting how they claim their PWM (or 'PDM') conserves power, while other controllers dump 100% of the power.  LOL


fabieville, MPPT needs to Track the available power.  Wind and solar are very different in their 'tracked' characteristics.

[Flux]

"with the manually control buck converter i would have to keep on adjusting it to suit the wind turbine?"

Yes. You may find that you can get a decent compromise setting. if it works well but needs constant changing it could be an incentive to build a simple controller for the converter pwm.

Flux

[bamfords54]

Lets see if this works Omron Overvoltage.pdf (103.38 kB - downloaded 489 times.)