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Alternator (but used for something different)!!! Help

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Peter.N.

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PostPosted: Mon Jul 25, 2011 8:07 pm Reply with quote

Hi John

The output from the generator on the small ones is AC, they have a permanant magnet rotor and usually a three phase output but they generally have a built in rectifier and sometimes a regulator.

I have a 250 watt 24 volt wind turbine with 2 metre rotor blade assy, it gives a good output in about a 10 mph wind. That has a 3 phase output with a seperate rectifier/regulator unit and a dump load resistor which is switched across the output when the batteries are fully charged. helps warm my workshop in the winter icon_biggrin.gif

Peter
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Burnerman (27 Jul 2011)
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Mursal

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PostPosted: Wed Jul 27, 2011 2:51 pm Reply with quote

Yes John, all AC and then rectified (no output brushes) some good conversion kits on E-Bay

http://bit.ly/otiZgz
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Ricardus

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PostPosted: Wed Jul 27, 2011 4:06 pm Reply with quote

Burnerman wrote:
We'd be interested to see how you are going to drive the alternator!


My grandad built himself one of these using (I think) the motor from an old washing machine.
Of course being my grandad it was painted in maroon and powder blue paint and health and safety was "Keep your fingers away from the belt when its running, boy, or you'll only be able to count up to nine." icon_biggrin.gif
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Peter.N.

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PostPosted: Thu Jul 28, 2011 8:57 am Reply with quote

They are a little notchy John but they have an umpteen pole rotor which reduces the depth of the notch. I wouldn't have thought that an ordinary car alternator would be suitable , the typical max output speed you get from a wind turbine with blades big enough to get a decent output is around 400 rpm which is OK with a permanant magnet alternator but it wouldn't think it would be fast enough for a wound rotor type.

Peter
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Burnerman

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PostPosted: Thu Jul 28, 2011 11:45 am Reply with quote

Yes, interesting post Peter and thanks for that icon_wink.gif
I guess an ordinary alternator wouldn't actually reach its cut in speed.
John icon_smile.gif
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GonzoUK

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PostPosted: Sun Mar 11, 2012 8:24 am Reply with quote

Hello Peter & john
I big thanks for your help so far, It's been some time I know, but have not been too well icon_cry.gif
Anyway an update, my first attempted to run the alternator failed but have not given up hope yet.

Anyway have put a backup plan in place and currently running the alternator by a 1 1/2 HP motor which the alternator once started and under load runs from an inverter, so it self-powers the motor : D

Now a quick question I want the alternator now to charge a battery bank of 12v batteryís the question is does the alternators have a built in charge control as such?

What I mean is letís say the alternator is on the car, does the alternator know when the battery is fully charged and then stop charging it or is there another bit of electronics on the car that does the charge controlling?

I have used the alternator already and can see its charging a battery but I donít want to over charge it.

Once I have this info I can finish of this project and share with pictures, may be even a little video icon_lol.gif

Look forward from hearing from all of you icon_mrgreen.gif
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GonzoUK

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PostPosted: Sun Mar 11, 2012 8:26 am Reply with quote

By the way the alternator pushes out 80 amps, and the motor only takes up 7 / 10 amps.

Thanks
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Peter.N.

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PostPosted: Sun Mar 11, 2012 9:24 am Reply with quote

Practically all car alternators have a built in regulator, it is designed to give a regulated output of a bit over 14 volts so when the battery is low the voltage difference will cause a high current to flow, as the battery voltage increases so does the difference and the current drops, when the battery is fully charged the voltage difference is small so the current is small, probably just an amp or two.

Peter
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GonzoUK (11 Mar 2012)
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Mursal

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PostPosted: Sun Mar 11, 2012 2:25 pm Reply with quote

Good to hear from you again, Gonzo

Yes that alternator in the picture has a regulator built-in. It's the black box that holds the brushes in place. So it wont over charge the 12V batteries.

About the motor/Alternator combo:

Power in = Power out + loss in the system
Voltage x Amps = Power in Watts

Unfortunately there is always loss in the system.

So you wont get FREE power?

Or if you do please let me know, I'll swim over specially to see it icon_cool.gif
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Inky Pete

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PostPosted: Sun Mar 11, 2012 4:27 pm Reply with quote

GonzoUK wrote:
Hello Peter & john
Anyway have put a backup plan in place and currently running the alternator by a 1 1/2 HP motor which the alternator once started and under load runs from an inverter, so it self-powers the motor : D



The output from the alternator powers the motor which drives the alternator?

Not heard of the First Law of Thermodynamics as applied to Conservation of Energy then?

http://en.wikipedia.org/wiki/First_Law_of_Thermodynamics

http://en.wikipedia.org/wiki/Conservation_of_energy
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mysteryman

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PostPosted: Tue Mar 13, 2012 10:46 am Reply with quote

Alternators normally run clockwise when looking at the pulley. It will charge if driven anticlockwise, but you should change the cooling fan in that case.

1970s Saab 95/96s with German Ford V4 engines drove the alternator and water pump anticlockwise off the pulley on the balance shaft.
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