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Generator Winding Pitch



I have a CAT 900kw 600v genset parrelled with a CAT/Kato 1000kw 600v genset.

I have quite high neutral ground current so i'm trying to find out if I have a winding pitch mismatch.

Can anyone tell me the winding pitch for the following 900kw CAT generator?

Model SR-4

Serial #4MD00737

Arrangement # 9Y-1411


Thankyou for your help in advance

Super Contributor

Re: Generator Winding Pitch

9Y1411 is .75 pitch.

New member

Re: Generator Winding Pitch

Thanks Dave

.75 or 3/4 pitch seems like a very odd pitch.

But hey, maybe that's why I am having issues.

Super Contributor

Re: Generator Winding Pitch

Actually 3/4 pitch is quite common in the oil field industry, CAT, Kato and Baylor all provide this pitch in a large number of generators. the Kato "oil field" tail ends are standard 3/4 pitch, as are most of Baylor's line.


If you bought a used tail end from someone without spcifying pitch, then there is a good chance you got an old oil field unit.



New member

Re: Generator Winding Pitch

You are absolutely right Mike

I found a reference on the gen nameplate that said it was designed foroil field use.

Totally appreciate your help.



New member

Re: Generator Winding Pitch


I'm getting into this discussion quite late but I've just joined the group.  I'm wondering if you were able to resolve the circulating neutral current problem. If not, there is now a simple and very effective solution (  Let me know if you have any questions.



Re: Generator Winding Pitch

[ Edited ]



We are planning to Run a gas engine in parellel to Existing CAT 3512B land Rig Engines,

Please can you give me Pitch of the below Sr. no/arr no of alternators.


7TN04192 / 320-3716

7TN05341 / 434-7058


even if its not possible to run different pitch of alternators in parellel, is it okay for a short time synchronization to change over from Gas genset to Diesel Genset, the purpose is to change over without a blackout.


at present we don't know the pitch of the gas gen Alternator, its Siemens 750KVA





Re: Generator Winding Pitch

Suresh, if you send us your inquiry to we can assist you with your neutral circulating current concern.  You can run generators with different pitches in parallel so long as you consider how to effectively prevent the neutral circulating current.