Author Topic: Generators  (Read 3488 times)

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harley1782000

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Generators
« on: April 16, 2010, 09:19:13 PM »
First I would like to say Nice job on the new board, love it.  Been awhile since I have been on.  On to my question, My Friend wants me to post this cuz I can not answer it for him.  Basically he has an old diesel motor that he runs bio fuel in it.  The motor it self makes about 80hp.  The question is how many car alternators can be run off of it and can they be hook up to a battery bank?  Basically the motor with 10 alternators on it charging a battery bank and then being hooked to the grid to sell back.  Now I know you are all going to say why not just get a big generator head.  He is cheap and likes to make things.  I have no clue how too hook that many alternators to gether to run as one.  No clue so if someone can help I will let him know.

bob g

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Re: Generators
« Reply #1 on: April 16, 2010, 09:52:13 PM »
short answer?  maybe as many as 20 car alternators, but

time you buy 20 from the junkyard, buy the special pulleys needed, and the belt
to drive them all (cog drive and double cog serpentine capable belt) and then figure
a way to regulate and control 20 alternators worth of field current (about 60-80amps)
he will end up with the following

and incredibly rube goldberg, horribly inefficient, and more expensive than it would be
to just go out and buy a 30-40kwatt ST head from Georgia generator

i am sure if he has to ask he has no clue as to the drive requirements, the mounting requirements,
or the insanely expensive field control regulator he will need to control this frankencharger.

and don't even think about using a reostat to control the field, it alone would be massive and bloody expensive
and there is no way he can control the current to the point of stable power generation by hand
it just isn't going to happen. a custom built regulator to control 20 fields would likely cost several times what a 30kwatt
st head could be bought for.

twenty alternators that are for instance 100amp units, equates to 2000amps, that alone will require massive cables
which cannot be connected directly to any of the alternators directly, so a buss bar and feeder cables would have to be
setup.

and i haven't asked yet what voltage is he wanting to generate, 12volts?

don't get involved with this project, nothing good will come from it.

ymmv

bob g
research and development of a S195 changfa based trigenerator, modified
large frame automotive alternators for high output/high efficiency project X alternator for 24, 48 and higher voltages, and related cogen components.
www.microcogen.info and a SOMRAD member

PeterAVT

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Re: Generators
« Reply #2 on: April 17, 2010, 08:22:52 AM »
80 horse diesel is good for about 50 kW. That means it's good for 2 houses at 100 amps service each. Roughly speaking. Your friend would be *way* better off to get a "farm generator" or "PTO generator". The kind you hook up to the back of a farm tractor. Just look in the classified ads or look for scrap or a deal. That's a darn big unit he's building, and it would be a huge waste to try car alts - prolly wouldn't work too good either. Worse comes to worst he could just do a really big axial flux like they build here.

The only way I would try 20 car alts on it, is to make a really long driveshaft with a set of bevel gears for each alt. Then use only one regulator with a really big series-pass transistor, or a bank of transistors to feed the exciter current.

Like Bob says, the easiest and cheapest way is to prolly get an ST generator head; you can find some decent size units on ebay for like $500.

harley1782000

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Re: Generators
« Reply #3 on: April 17, 2010, 08:33:48 AM »
Well that is what I told him, Useing car alternators would just be a big headache.  I am going to tell him too look for a pto genny.   Problem with Dave, my freind, He has way too much time on his hands to just sit around and think.  LOL.  Thanks for the info and I will let him know.