Do you have the exciter brush gear for the Pabst alternator?

DMahalko

Intermediate Poster
Going back to the video I shot on Monday, I see there is no brush gear installed on the exciter rings, so the Pabst alternator is almost certainly just dead spinning iron.

Do you have the brush gear for this alternator lying around somewhere?

Pabstexciterbrushrings.jpg


If some people concerned about damaging the alternator by increasing the engine to full RPM, it looks to me like that worry can be put behind you.

Generally as long as there's no power flow to the field windings, there is no power produced by an alternator/generator. The field has to be excited with current flow for the alternator produce anything or it's just a mass of spinning steel.

FYI, alternators are built in reverse of how you'd normally expect a generator to be built. The heavy high amperage current producing windings of the armature are mounted in the stationary frame, and the spinning rotor in the middle carries the input field coils. The field is a relatively high voltage with lots of coil windings, so they could make an alternator work with tiny little field brushes and do away with the complex monstrous brush assemblies of high current commutated DC-producing dynamos.

Small portable AC alternators are self-excited by a residual magnetic field in the rotor that kicks off the power production, but nearly all the big stuff like this is separately excited with a small dynamo (commutated DC generator).

It should be fairly easy to check it with a voltmeter to see that no voltage is present when it is spinning.


The only big question mark for me is that I don't see any signs of where a small exciter dynamo may have attached to this engine. Maybe a belt around the flywheel? Or was the exciter run from a separate smaller steam engine?

- Dale Mahalko
 
I was looking around the web site and came across this thread. I can't believe it slipped past unnoticed last September.

Yes, we do have the brush gear for the Pabst Engine. When you took this picture you could have reached out and touched the brush gear. The brush gear stands inside the fence near the alternator. It was very close to your left hand when you took the picture.

I believe the alternator was excited by commercial 110V elelctricity.

Later,
Jerry Christiansen
 
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