simoin

you've nailed it Nigel, that is exactly what i want to be doing, it is just coming up with a circuit that is on the market or indeed deigning something that can do this for me.... Any idea's there? I am willing to contribute towards costs etc, I would do it but simply do not have the experience necessary.

I do not believe the field is editable, but indeed I do not really know, what you were looking at in the last picture is basically it, there is that and the magnets on the outside, that's about as technical as this generator gets...

Nigel Goodwin

For a start I would suggest making accurate measurements on what the generator actually provides in the different configurations, at different speeds. Make sure it's viable, and find what speed is the optimum changeover point.

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simoin

i will do my best to make mesurements but assuming it did make a reasonable difference what then. I would like to be able to adjust the changeover point to set it at the optimum after the control board is in place perhaps with a trim pot controller or something...

Nigel Goodwin

Depending how you design it you could certainly use a pot to adjust the switching point, or you could do it in software if you use a micro-controller for the job.

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Hero999

The field current doesn't take much power and it's required anyway providing it doesn't have a permanent magnet rotor. Therefore it makes a lot of sense to reduce it at high speeds so the voltage doesn't exceed the battery's maximum and increasing it at lower speeds will make the alternator more efficient since it will be producing power that would otherwise be wasted.

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Nigel Goodwin

I would disagree, the field current takes a fair amount of power - which you can't afford to waste in something like this - any power going to the field coil isn't going in to the battery!. Using a permanent magnet means you get maximum power all the time - when the battery is fully charged you dump the excess to a dummy load. This may sound wasteful, but it's no different to the field coil - where you're still wasting wind energy once it's fully charged.

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Hero999

Why is it that they use field wound machine in cars then?

To get an output at different speeds; isn't that what we want?

Also note that I'm saying you should keep the field carrying current continuously (like I said before) there come a point when it isn't profitable to keep it powered and there should be a switch to disable it.

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HarveyH42

In a car, the alternator is spinning fast enough to be self powered when the engine is idling. Once the car is started, you don't even need the battery.

The wind doesn't blow constantly or consistantly, so you need to store what you can. Field windings instead of permanent magnets would use power, and you would have to wait and measure RPMs until the speed came up enough to produce more energy then the field would consume. So, yes the magnets put drag on the rotor, but that's another design issue.

My wind power experience has gotten past stepper motors and LEDs (no batteries yet). Tomorrow should be our first tropical storm through central Florida, so get to see some bright flashing lights, or maybe searching the yard for pieces...

williB

There is no field winding on a F&P alt/motor.
it is a permenent magnet three phase motor ,which makes it a very nice three phase windturbine alternator

Pommie

Wouldn't the most efficient system be a star configuration with a SMPS to convert to 12V. The diode losses at high voltage/low current are reduced considerably and SMPS are very efficient.

Mike.

Nigel Goodwin

Because you have energy to burn, and it's a VERY easy and effectvie way to control the amount of energy output.

No, we're wanting the MAXIMUM possible energy from the wind.

????? - no field current, no output (well hardly any), what good is that?. And on the other hand, you need maximum field current when the alternator is spinning slowly - energy you can't afford - particularly when it gives no advantages for a wind generator.

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HarveyH42

Well, the savonius didn't make it through the night, top section came off. Will re-glue it when it dries off. The propeller version is still going strong. Funny thing, the storm we had last night wasn't Tropical Storm Barry, late this afternoon I'm guessing.

simoin

okay so I have my 3 phase Permanent Magnet generator, now how do I switch from star to delta when the wind kicks right up?

Pommie - stupid question for you, what do SMPS do? I was just going to rectify it to 12volt using 50Amp car rectifiers. I have a diagram for there hookup at home somewhere.

Sorry to hear your savonius did not last through the start of the storm.

I have also talked to Ed from: www.windstuffnow.com/main - who says:

The controller I used was from design specialists as you posted on the alternative energy site. I don't believe he is building them or any other kits right now. Really to bad for us, they worked great as well did his tack jr. I don't know of any thing out their comparable to it.

--

So this means no one has a product like this and for some rising entrepunear that there would be a market for a product out there... I think we have also established that a field current generator thing is not going to happen as this is a PMG device...

HarveyH42

The savonius rotor was more of a toy, first one I threw together to see how steady and how big (wasn't big enough). Will give it another try sometime.

Switching the winding configuration doesn't seem that bad. Might be able to measure the output voltage, and switch when it's much higher then what is needed to charge the battery. Just need to determine at what point you will still get more then 12 volts, when you go to the higher current configuration.

JTECH

Hi folks! As far as I can understand about wind turbines/generators, is that usually the field cannot be adjusted electrically, because it consists of permanent magnets. One should look at a mechanical means of adjusting the air gap between the magnets and the stator, i.e. reducing the gap proportionally as the speed increases in order to get the most out of the available wind. At low speeds, a bigger air gap means less "cogging" and the machine can speed up easier. Come on, let's hear from the mechanical-inclined people on this forum!
Regards all.