Moans and grones from one winding but not the other?

[playdiesel]

I have my 15KW unit wired for 220 and two sets of 110V recepticals, one wired to each leg of 220. Under any load one sides  hums, and slightly vibartes. Plug the same load into the other side and it makes no noise. When I look at the drawings I see only two parts that are not common to both sides, the stator windings, is that correct? I have read all the moaning and groning posts but none where it happened only on one side. I am not very lectro litterate, sorry. How do you check things like the stator windings for being loose?

[OilCan]

I am assuming you have U3,U4 bridged together.  220-230V available at U1,U2.

You have a 115v recept. across U1 to U3/U4.
You have a 115v recept. across U2 to U3/U4.

Are the voltage measurements approximately equal between U1 to U3/U4 and U2 to U3/U4
no load?

*U3,U4 become floating neutral, not bonded to chassis ground or also called an ungrounded centertap.  The neutral side (white wire) of your house receptable is "grounded" neutral, bonded in panel box.
Making contact with floating neutrals can be lethal, as you may be grounded and become a conductor to ground.  Just a warning.

Which connection under load makes the noise?  U1 or U2?

Have you Ohmed U1 to U3 and U2 to U4 unconnected to posts?

Are the readings similiar?

That's it for now.

[playdiesel]

Thanks for responding, I have read the other questions and answers about unbalanced 110 loads on an ST wired for 220 but none of the noises/conditions like mine. Another thing I have found is I if I have a load on the side tha makes noise it goes away if i apply any load to the other side, not an equal load, just any load.

I am assuming you have U3,U4 bridged together.  220-230V available at U1,U2.This is correct

You have a 115v recept. across U1 to U3/U4.correct
You have a 115v recept. across U2 to U3/U4.correct

Are the voltage measurements approximately equal between U1 to U3/U4 and U2 to U3/U4
no load? With RPMs set for 60 hertz they are 125.5 (U1) and 124 (U2)
*U3,U4 become floating neutral, not bonded to chassis ground or also called an ungrounded centertap.  The neutral side (white wire) of your house receptable is "grounded" neutral, bonded in panel box.
Making contact with floating neutrals can be lethal, as you may be grounded and become a conductor to ground.  Just a warning.
I am just learning about how to properly ground my system for my usages. Part of the time I will be using mounted 110V recepticals for general use like power tools when commercial power is not close by.  Part of the time we will be using it for emergency power by feeding the 220 to the house main via 4 conductor S-O cord and proper switching. As it is currently wired I have the neutrals from both the 110 recepticals and the 220 breaker for the S=O cord running back to U3/4. A separate chassis ground wire ties the frame of the gen head to the boxes and to the third prong of the 110 recepticals and will connect to the gounding at the house via the forth wire in the S-O. Thus my grounding is not bonded at the head but back at the main when plugged in and never bonded when operating unconnected to the main

Which connection under load makes the noise?  U1 or U2?U2

Have you Ohmed U1 to U3 and U2 to U4 unconnected to posts?No

Are the readings similiar?

[sailawayrb]

I think all STs moan and groan when wired for 220 if you have unbalanced 110 loads.  Unless you really need 220, always best to wire for 110 so unbalance is no longer an issue.  Furthermore, if you ever need 100% ST full rated power for a 110 circuit, you must wire for 110 otherwise you can only get 50% ST full rated power...assuming you don't want to mess with adding transformers.  I wired my ST5 for 110 and I feed it to both sides of CB panel (via a transfer switch for safety) with cable that can handle the full amperage (5000/110=45 amps).  Of course, I can only feed 110 circuits, but I don't have to deal with load unbalance or transformers, and I can feed 100% power to any 110 circuit (or 100% to each side of CB panel instead of only 50% to each side if wired for 220).

[playdiesel]

Ya, thats what I mean about mine being unusual. It moans not a bit when you load the U1 side hard and U2 moans just a loud with a 100 watt bulb as it does with a 1500 watt heater and it will quit moaning no matter how heavily it is loaded when any load, even a light bulb is connected to  U1. I need to be wired 220 for it to be of any use as emergency power at the house as we have several 220 needs.  Has anyone every assertained that there is damage from the moaning or is it strictly an ear irritation?

[sailawayrb]

That is a very interesting biased effect indeed, but I don't know if it's unusual as I don't recall if equivalent load unbalance on one or both sides of mine resulted in equivalent moaning?  I also don't know if moaning is significantly detrimental, but I could see how significant unbalanced rotation could perhaps shorten bearing and brush life.  

I wonder if you changed the direction of rotation, if the same side would still moan and the other side would not?  I guess I am thinking there could be an inherent weight unbalance that is causing a biased unbalanced rotation and the biased effect you described.  As you know, when wired for 220 with unbalanced 110 electrical loads, you create unbalanced magnetic forces which create unbalanced rotation.  If there was some weight unbalance when electrically unloaded, introducing unbalanced 110 electrical loads could increase or reduce the rotation unbalance depending on which side had the unbalanced electrical load (i.e., the biased effect you described).  However, I think you indicated that when completely unloaded, you don't get any moaning...and one might expect that one would get moaning if there was an inherent weight unbalance...so this train of thought isn't conclusive...

If you haven't already, you might want to do some reading here:

http://www.utterpower.com/ST.htm

and check the links at bottom regarding wiring, grounding, troubleshooting, etc.  Maybe you have cheap bearings filled with Yak fat

[playdiesel]

Could be yak fat, cant seem to keep the darn dog away from it, LOL