Author Topic: 80cc engine + alt  (Read 3889 times)

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Offline excaliber

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80cc engine + alt
« on: November 23, 2014, 11:32:58 am »
New here so I am not sure if I have put this in the right place. I have built dual rotor alts before but not something thats engine driven and am looking for some direction as to the winding's.
This engine was hooked up to a 1200 watt alt 120volts ac 10 amp, I have removed the alt as you can see, then measured for the room to mount a flywheel,  I have room for a 8 to 8.5 inch disk, I am thinking half inch thick. I would like to just use a single rotor, I dont want a lot of weight hanging of the end of this shaft.
So lets say a single 8 inch disk, 1 inch round neo mags, 1/4 inch thick (maybe 3/8th), a 12 mag 9 coil arraingment. target RPM's 1800- 2000...DC amps out for a 12 volt system around 20 to 30 amps . for a hard number lets say 25 amps.
thought's any and all please..Gauge, winding turn's, delta, star?

Offline dang

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Re: 80cc engine + alt
« Reply #1 on: November 23, 2014, 10:43:13 pm »
that close to the engine you will need to provide heat shielding and some cool air slinger/impeller air mover functions...
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Offline bj

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Re: 80cc engine + alt
« Reply #2 on: November 24, 2014, 07:16:48 am »
   As Dan said, heat could be an issue, in more ways than one.  Working hard, at that low an rpm, the engine
will not be happy either.  Their cooling is best at governor rpm.  (usually 3600)  Maybe consider a belt drive,
to allow the engine to run at governor rpm?
   As to alt design, there are many that will give you better info than me.  I have built quite a few
gas powered units, but always used an automotive alternator.
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Offline excaliber

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Re: 80cc engine + alt
« Reply #3 on: November 24, 2014, 12:36:07 pm »
thanks for the concern about heat, I do understand what you are saying, have plans for ensuring thats not a issue.  Right now I am running this unit down at 54 volts out of the ac alt, at a freqency  of 42 hrs. Rpms must be around 2500 or so. No problems at all.this drives a oldwelder transformer that has multi taps on it..the one I have it on now at this low rpm gives me 20 amps dc out for batt charging. I just cant go lower on the rpms or use  other taps as doing so collapses the field in the alt. I would like to get rid of the inefficiencies of the alt and this transformer/charger and just build one direct 3 phase alt. Its the windings, gauge, number of turns,at 1800 that have me stumped, while I have built dual alts before, with this single disk alt i want to build, I have found a product I would like to try. Its a composite material that I would machine and wrap my coils directly to..then maybe cast if needed
I did think of using a car alt as you have done but at efficencies of roughly 50 pecent using them I really need better with this small engine...

Offline Watt

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Re: 80cc engine + alt
« Reply #4 on: January 02, 2015, 09:45:04 pm »
I think I'd build the rotor the size and with the magnets I'm going to use.  Decide the coil size by drawing out the stator on a piece of paper just as I'm sure you have done before.  Grab whatever size wire you have ( You'll need to know the size of wire you used ) and wind a coil to fill the area of the single coil completely.  Then run the engine/rotor with the test coil in place at your desired rpm's and get an oc voltage at each rpm.  Then do the math for required voltage you need say ~12vac.  You will probably have to have a quite a few strands of larger gauge wire at that low a voltage but, you will know by how many wraps of the single coil and rpm.  You may do well to have a second blank rotor for return flux but, with enough rpm, you may be alright with 25a.  Have you thought of using a mppt controller?

With the sorta rpm you are thinking of running, you may wanna think about delta for a bit more current.  You don't have to worry about cut in or any of the like so....  As has been said, there are plenty of experts that can give a few better words of advice...  Good luck and post your project as you make progress.

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