generator

[Tom Wesenberg]

John Regan makes a regulator that looks like a cutout and you use the third brush to set the maximum output. I make an electronic voltage regulator that fits in place of the adjustable brush, and uses the stock cutout on top of the generator.

The cutout is simply an off/on switch that turns off when the generator output falls below battery voltage. This keeps the battery from feeding back into the generator and killing the battery or burning up the generator, or both.

[Joe K]

Disconnected from the battery, a Model A generator will put up to (possibly) 32 volts depending if you hit that 'sweet spot' where the 3rd brush position maximizes output.

In real life if you paired the generator up to a 6V battery and generated 32 volts, you'd seriously overcharge the battery in short order.

Thus, normal positioning of the 3rd brush is to make the generator generate about 8 volts (say) and maintain anywhere from 5 or 6 to possibly as much as 10 amps (or even a skosh more if you do a lot of starting at night when the engine doesn't get a chance to catch up on charge.) We're not so much interested in voltage because in these ranges, the battery holds it all back to about 6.5 or so (and so you don't blow light bulbs.)

Not sure of what he has left you with his "all dressed up and nowhere to go" generator. He may have been headed for a totally regulated circuit? There are different ways to accomplish the thing most of them done by regulating the generator field and doing away with the adjustable brush altogether.

I'm not sure how Tom does it, but he may keep the 3rd brush and use that output with his regulator.

Take a look at the Ford wiring diagram, which if you zero in on the generator alone, gives you that "stock" wiring. Perhaps you can correlate to this and get your electrical bearings and figure out what you have. Tom (and I with less assurance) will give you clues later as to polarity, flashing the generator, and other details which can undo all your close examination and attempts to make something work.

Wiring diagram at http://www.webjunk.com/modela/wp-con...amcolor2sm.jpg

The Model A generator is seriously simple, as you can see.

Joe K

[marc hildebrant]

Joe K,

Actually, the third brush regulates the amount of current only as the Model A generator is a constant current generator. Thus, for a constant current device, the voltage rises or falls to make the amount of current equal to what the third brush is set to. That's why the voltage rises to such a high level when the generator's output is disconnected...it's trying to push current into an open circuit and only knows to keep raising the amount.

The battery keeps the voltage to the proper value and the ammeter shows how much current is going into the battery.

Sorry, but I don't have a better explanation.

Marc

[Joe K]

Originally Posted by marc hildebrant

Joe K,

Actually, the third brush regulates the amount of current only as the Model A generator is a constant current generator. Thus, for a constant current device, the voltage rises or falls to make the amount of current equal to what the third brush is set to.

The battery keeps the voltage to the proper value and the ammeter shows how much current is going into the batter.

Marc

It takes a voltage higher than the battery cell voltage to put ampereage TO the battery. Just as a voltage lower than the battery cell voltage allows current to return to the generator were it not for the cutout.

In practicality, the voltage changes are relatively small and the battery acts as "electrical flywheel" taking on and giving out electrical energy as required.

I tink we both said the same thing but with a different focus.

Joe K