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From: RB on 25 Mar 2005 12:44
I am asking for help in getting educated in voltage regulators for small gas
engines. Here, I'm speaking of the kind that have a starter unit separate
from the alternator.

I'm getting all sorts of mixed signals as to what will or won't work with my
17hp garden tractor.

My dealer wants $100 for a new one, and I'm reasonably sure I can get by
with much less money out of pocket than that.

Ebay has maybe 20 pages of voltage regulators.

My contention is:

1. HP---engines or roughly the same hp should have charging systems scaled
accordingly. Is this more or less true?

2. That a 12v regulator is a 12v regulator, is a 12v regulator, as this
refers to output dc voltage.

3. That the size (amp rating) of voltage regulator matters only insofar as
your need to provide a given max charge rate to the battery---i.e., we can
use a bigger of smaller regulator than the system design/spec rate, and all
it does, if the one we choose to use is smaller, is restrict the rate the
battery will charge up.

I think I could use just about any of these that match up roughly to the amp
rating I need, the 12v rating, single phase alternator (most small engine
garden tractor ones are single phase), and 3 wires out of the voltage
regulator.

I understand the 3 wire thing is standard for simple circuits. Two leads go
to the alternator ac output, and one goes to the battery.

If the case isn't grounded, then a 4th wire is needed for a ground.

So, my garden tractor is specified to have a 20 amp system. Any reason that
just about any 3 wire, 20 amp, 12v alternator wouldn't work with my engine?

So, there are my perceptions and ignorance. Now, please set me straight.


From: Franc Zabkar on 25 Mar 2005 16:44
On Fri, 25 Mar 2005 11:44:03 -0600, "RB" <rbig(a)bellsouth.nospam.net>
put finger to keyboard and composed:

>I am asking for help in getting educated in voltage regulators for small gas
>engines. Here, I'm speaking of the kind that have a starter unit separate
>from the alternator.
>
>I'm getting all sorts of mixed signals as to what will or won't work with my
>17hp garden tractor.
>
>My dealer wants $100 for a new one, and I'm reasonably sure I can get by
>with much less money out of pocket than that.
>
>Ebay has maybe 20 pages of voltage regulators.
>
>My contention is:
>
>1. HP---engines or roughly the same hp should have charging systems scaled
>accordingly. Is this more or less true?
>
>2. That a 12v regulator is a 12v regulator, is a 12v regulator, as this
>refers to output dc voltage.
>
>3. That the size (amp rating) of voltage regulator matters only insofar as
>your need to provide a given max charge rate to the battery---i.e., we can
>use a bigger of smaller regulator than the system design/spec rate, and all
>it does, if the one we choose to use is smaller, is restrict the rate the
>battery will charge up.
>
>I think I could use just about any of these that match up roughly to the amp
>rating I need, the 12v rating, single phase alternator (most small engine
>garden tractor ones are single phase), and 3 wires out of the voltage
>regulator.
>
>I understand the 3 wire thing is standard for simple circuits. Two leads go
>to the alternator ac output, and one goes to the battery.

I would offer advice, as I've actually built regulators for mining
equipment, but I've never seen an alternator that had an AC output.
All have had internal rectifier diodes (which would be cooled by the
alternator's fan). Does your regulator provide the rectification?

>If the case isn't grounded, then a 4th wire is needed for a ground.
>
>So, my garden tractor is specified to have a 20 amp system. Any reason that
>just about any 3 wire, 20 amp, 12v alternator wouldn't work with my engine?

The alternator may have a floating field, a grounded field, or a field
that is tied high. You will need a different type of regulator for
each configuration.

>So, there are my perceptions and ignorance. Now, please set me straight.

Do you have a wiring diagram for the tractor?


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.
From: NSM on 25 Mar 2005 22:09

"RB" <rbig(a)bellsouth.nospam.net> wrote in message
news:33Y0e.53744$c72.36799(a)bignews3.bellsouth.net...

> I think I could use just about any of these that match up roughly to the
amp
> rating I need, the 12v rating, single phase alternator (most small engine
> garden tractor ones are single phase)

Are you sure? Most auto ones are 3 phase. Anyway, even an old auto one could
be cobbled to work. It's a matter of physical fit mainly.

N




From: James Sweet on 26 Mar 2005 14:48

"NSM" <nowrite(a)to.me> wrote in message news:Rn41e.7130$x8.232(a)edtnps90...
>
> "RB" <rbig(a)bellsouth.nospam.net> wrote in message
> news:33Y0e.53744$c72.36799(a)bignews3.bellsouth.net...
>
> > I think I could use just about any of these that match up roughly to the
> amp
> > rating I need, the 12v rating, single phase alternator (most small
engine
> > garden tractor ones are single phase)
>
> Are you sure? Most auto ones are 3 phase. Anyway, even an old auto one
could
> be cobbled to work. It's a matter of physical fit mainly.
>
>


He's right, most small engine alternators are single phase, they're nothing
but a coil mounted near the flywheel to get their energy from the magneto
magnet.


From: NSM on 26 Mar 2005 22:57

"James Sweet" <jamessweet(a)hotmail.com> wrote in message
news:w0j1e.2502$Go4.2147(a)trnddc05...

> He's right, most small engine alternators are single phase, they're
nothing
> but a coil mounted near the flywheel to get their energy from the magneto
> magnet.

OK. I've seen those as a sort of magneto. Do they have a diode rectifier?

--
N

















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