Putting generated power into 12v battery

[nirol]

I have made a wind turbine with a three-phase generator/motor. It puts out great power but its useless unless I can overcome the problems. Its 83volts ac max between two phases in a good wind. It needs to be left unloaded under about 25 volts ac so the blade has enough momentum to get started and not stall. If I rectify it directly to a 12v battery it produces about 100 watts, - to 24v = 200 watts and if put into 48v
(4 batteries) up to 500 watts. Problem is it needs to go into a 12-volt system. Three transformers? MPPT like on solar panels? Or is there a fancy regulator? What old appliance could have a suitable transformer?
(to fit into a students budget if at all possible) It looks like it could put out up to 40 amps total, would one transformer have to handle a third of this? I’m estimating the transformer ratio to be 4/1. Also it seems to put out best power in star, this increases the dc-rectified voltage so I am not even sure if that ratio is enough. Well its just a lot of head scratching for me so I really appreciate any assistance :roll:

 

[nettron1000]

Does your three phase generator/alternator have field coils or does it use permanent magnets ?

Alternators in most vehicles use a regulator that controls the voltage in the field coils so they can be relatively low power.

If your generator uses permanent magnets you'll have to try doing it the convensional way.
Heres my suggestion :First you'll need to convert the 3 phase to single phase, this is usually done with a 3 phase to single phase transformer, good luck in finding one of those. Another way is to use three single phase transformers , actually that idea is used in some arc welders, but you'll have to get transformers that are rated for the current of the load you are using. You may have some luck finding a suitable transformer in some discarded power amplifiers or stereos.
Next you'll need a bridge rectifier with proper filtering, again the power handling capability of the bridge is determined by the current draw of your load. Then use a suitable voltage regulator circuit rated for the expected current draw of your load.

 

[nirol]

I rang a local technician the other day and he suggested the same idea of using transformers out of power amplifiers, he said he had one, maybe that’s the answer if I ring around I may find another two, I don’t know if any power handling variation would make a difference? It is a permanent magnet motor. I think it use to run on pulse dc.

 

[nettron1000]

nirol, obviously this isnt an ideal perfectly engineered idea, like you said you'll have to search around and use what you can find.

Look for transformers that putout atleast 12 volts AC, they will be rated in VA ( volt-amps) this can loosly be thought of as the equivalent of DC watts. So for example if you find a transformer rated for 50VA @ 12 volts rms it will output a max current of 50/12~ 4 amps, if the rating were 100VA it would be doulbe this at ~ 8 amps.

Something else you must keep in mind is that transformers are effected by the frequency of the AC voltage driving it. Your windturbine driven generator will put out different frequencies depending on how fast the blades are turning. Most power transformers are rated with 60 or 50 Hz in mind. Frequencies above this will increase the inductive reactance of the coils in the transformer. So you can see how the mathematics of determining this can get quite involved.

You'll have to experiment with what you have and see what works best. You should also do a search on Google for homemade wind turbines and see what they are doing.