Newb looking for some information about gen head

[highroad281]

Greetings,  and apologies in advance if my questions have been previously addressed.  I have searched and researched but can't seem to clear up the bit of theory that I am apparently missing here.  Hoping someone will be willing to set me straight!   

The project :
I'm collecting the pieces to build a 12/2 genset. In my possession are:
A 12/2 FieldMarshal fairly fresh from a crate awaiting teardown.
An 8kw Winco gen head with model #8ks4gc 3/a. 

My questions are about the windings on the gen head and if/how they might be used creatively in this application.

On a typical ST head it looks like there are only two slip rings. 

On this Winco there are four (AC1, AC2, AC3 to rectifier, and Q for DC).

Questions : 

What are the DC slip rings used for in this model -excitation, etc?  I don't see any DC out capabilities in the factory config.  Could they be used to start the beast, or for charging maybe?

I know it's a good head and makes good power, have been PTO driving it during power outages for a few 14 hr runs with good results.   Since I'm in the planning stages I'd like to better understand what I've got an how best it might be used.   The only diag I can find is from Winco, and is attached.   

Any thoughts or advice would be greatly appreciated!   

-NE

[Thob]

I'll take a wild guess based on what I see in the pdf you provided.  The armature (the part of the generator that turns) has two AC windings on it.  The first is for output power, and is center tapped.  The center tap is connected to slip ring #2, the two hot legs are connected to slip rings #1 and #3.  The second winding provides AC to power for the field (stationary) winding.  This winding is also connected to slip ring #2, and to slip ring "Q".  The brush for slip ring #2 is connected to ground, and also connected to one of the AC inputs to the bridge rectifier (square box on page 2 that is turned 45 degrees).  The brush on slip ring "Q" connects to the other AC input of the bridge rectifier.  Output from the rectifier is DC (pulsating DC) and powers the field winding thru wires labels "short" and "long".

I don't think the machine can be used for starting or providing DC out for battery charging.

But then I'm pretty much guessing at a long distance - it's kind of difficult to analyze without being right at the machine.

[highroad281]

Thanks Thob, I appreciate your input.   Guess I need to take the covers off and get some detailed photos...   Will attach as soon as I can.   

[highroad281]

After taking a closer look at the armature I see what looks four collections of wraps ( opposite poles) but I guess this is two complete windings.   The output of the DC brush assembly definitely grounds back to the G2 white lead and also connects to the field coils...  it doesn't look much like what I have been seeing in the ST docs but I believe you were right on Thob, thanks for helping me see what should have been a little more obvious!   

Would be curious to see what a setup with extra start windings looks like if anyone has something to share.  Does it simply look like a 3 phase head?

Much appreciated!

[mike90045]

my head has 2 slip rings and 4 brushes, to insure a good connection (2 brushed in parallel)

[EdDee]

Of the two heads I run, both have 2 slip rings, with 2 brushes each as well as a separate DC commutator inboard of them closer to the rotor poles. One head has DC start capabilities (It is a Hoffberg) and has 4 brushes on the commutator spaced at roughly 90 degree intervals, the other is non dc start and only has 2 brushes...

[highroad281]

Call me dense but after staring at it I still don't really understand why there are 4 slip rings and 4 brush pairs on this unit if it only has two windings  Taking the armature out and taking a closer look might clear things up, but since it ain't currently broke I'm reluctant to mess with it too much.   

It makes sense that a gen head with dedicated start windings would be set up with a commutator like a starter has.  I read today that any motor can be made to generate,  and that any generator can be made to motor in the right conditions...  would that be considered non-DC start as mentioned above?  I'm still curious if there is there some mechanical switching arrangement that could be used to do this too even with only two windings and a power source? I have seen something similar referenced in older threads, maybe I'm simply misunderstanding.

Again,  sorry if these questions are ignorant and for subjecting you to my learning - I'm definitely no EE!