voltage regulator query

[RB]

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.

 

[Franc Zabkar]

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

 

[NSM]

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

 

[James Sweet]

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.

 

[NSM]

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?

 

[RB]

}}} 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? {{{

Right you are. Most of the bigger ones (cars & trucks, etc), have DC
output. And yes, they have internal recifier networks.

The small gas engine ones use a simple one that brings AC out. The voltage
regulator unit is actually dual function. It has a rectifier network, and
then, somehow, purports to regulate. I think the regulation is mostly a
figment of someone's imagination, as there doesn' seem to be anything in
most of 'em except a resistor or two. Anyway, it does purport to regulate
the recitified DC it produces.

}}} they're nothing
but a coil mounted near the flywheel to get their energy from the magneto
magnet. {{{

This is close to the truth, but still misleading. The magneto he speaks of
is simply a ring of magnets glued around in a ring on the face of the
flywheel which rotates past a stator coil to get ac. When we say magneto,
we normally are thinking of the thing that helps make the spark for firing.
This alternator is a form of magneto, but is different not the normal
ignition magneto.

 

[Franc Zabkar]

}}} 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? {{{

Right you are. Most of the bigger ones (cars & trucks, etc), have DC
output. And yes, they have internal recifier networks.

The small gas engine ones use a simple one that brings AC out. The voltage
regulator unit is actually dual function. It has a rectifier network, and
then, somehow, purports to regulate. I think the regulation is mostly a
figment of someone's imagination, as there doesn' seem to be anything in
most of 'em except a resistor or two. Anyway, it does purport to regulate
the recitified DC it produces.

I could imagine a regulator consisting of two pulse width modulated
SCRs with some minor support components. The switching noise wouldn't
be that serious in a tractor.

}}} they're nothing
but a coil mounted near the flywheel to get their energy from the magneto
magnet. {{{

This is close to the truth, but still misleading. The magneto he speaks of
is simply a ring of magnets glued around in a ring on the face of the
flywheel which rotates past a stator coil to get ac. When we say magneto,
we normally are thinking of the thing that helps make the spark for firing.
This alternator is a form of magneto, but is different not the normal
ignition magneto.

- Franc Zabkar

 

[Jim]

I could imagine a regulator consisting of two pulse width modulated
SCRs with some minor support components. The switching noise wouldn't
be that serious in a tractor.



- Franc Zabkar

I am wondering if you have a john deere 317 mower tractor? these came
out with a kohler 2 cylinder air-cooled engine or a 2 cyl onan
air-cooled. either engine has approx. 12 charging coils mounted
stationary inside the flywheel and output alternating current at
approx. 13-14.5 volts. this ac voltage brought out via 2 wires to a
connector plug which goes to the rectifier ( voltage regulator ). the
(vr) has 3 wires -2 ac in & 1 dc out. this goes to a plug which
carries an ignition, lights, electric p. t. o. clutch (some models) &
the charging voltage back to the instrument panel. check all plug
connectors ( at vr , main harness &the plug coming out of the flywheel
area.) if the engine is a kohler, the part # from john deere is AM
106357 which is $42. good luck.
Jim

 

[James Sweet]

The ones I've seen use the same magnets used for the ignition magneto, the
coil is just mounted in a different location around the circumference.
That's certainly not to say other types aren't in use, most of the small
engines I've worked on didn't have any sort of charging system at all so I
don't have a lot of experiene there.