Failure cause and grease aspect in 2 Speed Low Voltage wind generator

[petronila]

Hello All

The attached file shows some pictures of grease appearance and failure in a winding.

What do you think? Is this grease contamined? with what?

What could produce this failure in the winding?

The wind generator is two speed with independent windings. Thanks for the Inputs

Regards

Carlos

 

[burnt2x]

It's Mobilith alright! I can't miss that red color.

I've looked at the attached pictures and it looks like oxidation of the base oil in the grease resulting into thickening. That thick silvery thing looks like the grease contaminated with the wear materials. Please make a call to the manufacturer and see if they can help you.

 

[electricpete]

You probably can analyse a lot better than the rest of us being next to the machine, not to mention your experience.

One thought: if you look at typical grease compatibility charts, under thickener type “Lithum Complex” (like Mobilith SHC100), you will see the following thickeners listed as incompatible:

Clay
Barium Complex
“Common” Polyurea (*)

Incompatible means a significant change in “worked penetration” during testing, which can make it either thicker or thinner. I think what you’re describing is that there is residual grease which does not appear to have been overheated, but is much thinner than normal (correct?). In that case, one possibility (among many) is that the bearing has been lubricated with incompatible grease that caused thinning and running down onto the winding.

What about the grease on the other side of the winding (inside the inner bearing cap)? Does it show similar change in consistency? If not, might possibly tend to support improper grease addition on the side we’re looking at which is where grease is normally added. If yes, have to start thinking of other possibilities and other types of contaminants. (For example perhaps gases emitted from failing winding would penetrate through both sides of bearing and might possibly interact to change consistency.)

* Note “Common Polyurea” means non-shear stabilized. Polyrex EM is shear stabilized and should be relatively compatible with Mobilith SHC100.

Was there any info from the owner on types of grease was routinely added to this bearing for regreasing? Temperature leading up to failure? etc.

Is the picture upper right the opposite end from the picture on middle left and bottom left?

What are the symptoms of the winding failure? Have you localized a fault location. Usually failure in the endwinding would be turn-to-turn which results in very noticeable damage... it’s not clear to me whether that’s present. If it is just a ground fault without obvious evidence of turn fault, then more likely it may be in slot section where grease is not as likely to be a factor.


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(2B)+(2B)' ?