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wide range DC to 13.8V DC converter

Hi,

I am trying to figure out how I can make a regulator for a small wind turbine. The output is to charge 12V lead acid batteries.

The turbine outputs from 0-110V - (usually around 20-30V). The normal approach is to regulate to 13.8V, and dump the excess voltage through a shunt resistor. However this seems very wasteful, and I was wondering if there is a way of converting the excess voltage to current?

A long winded way would be to convert the input to a simple square wave, and pass it through one of set of transformers, which is automaticaly selected based on the input voltage. So T1 could deal with voltages 20-30V, T2 30-50V, T3 50-80V... Then rectify and regulate the output to 13.8V. As I say, long winded! And there has to be a better way!

Ideas?

Reply to
chris
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You need a buck switching regulator, which would convert available power to battery charging power at ballpark 90% efficiency.

How much power (in watts) does the turbine generate? How much current can the battery stand?

There may be a standard module available that does what you want. Vicor? It's not exactly a beginner's project to design a good, efficient, wide-range, current-limited buck switcher.

John

Reply to
John Larkin

Switching regulator?

Reply to
PeterD

How much current can the turbine output? or whats its power rating?

Reply to
Jon Slaughter

meci.com had a bunch of DC-DC convertors....

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Reply to
David Lesher

Buck converter.

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Assuming that the current/power are relatively low (otherwise the shunt resistor approach wouldn't be realistic), and you don't need particularly high efficiency (it couldn't be any worse than a shunt resistor), this isn't that hard.

You can get dedicated chips which will do most of the work (search for "switching regulator"), but at low power you could probably get away with just using an op-amp wired as an inverting comparator with some hysteresis: if the output voltage is too low, turn the switch on, if it's too high, turn it off.

Reply to
Nobody

Thanks for the info.

The turbine is rated at 100W, and can deliver around 8A. But I would rather over-spec anything I connect to it as in high winds it may output more.

If modules are available, I could presumably connect several in parallel to achieve the current handling?

Reply to
chris

I have thought about this problem before.

It is a complex load matching problem. The electrical load that the turbine feels will directly effect the mechanical resistance of the turbine. But for any given wind speed there is an optimal rotation speed to deliver max power. That is, as the wind speed goes up, you can ratchet up the resistance on the turbine. But if you ratchet it up to high, too soon, the turbine will enter into an inefficient aerodynamic region, and no longer deliver loads of power.

Furthermore, depending on the state of the battery, there is a max power it can accept (going down to near zero when the battery is fully charged). In case the turbine is delivering more electrical power than the battery can accept, you need to dump that power into some kind of heating device (resistor or transistor load).

If you have something that works already, and was designed by professionals, I would not try to improve on it.

--Mac

Reply to
foobar

chris snipped-for-privacy@hotmail.com posted to sci.electronics.design:

Probably not, unless they were specified to do that.

Reply to
JosephKK

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