Alternator Stator Windings Insulation

C

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champion_ip4p

Somehow if a significant amount of water content gets inside an alternator with VPI winding in running condition not synchronized, then what steps should be taken?
 
I had to look up VPI, and here's a very informative link:

http://www.electricmachinery.com/about-Duraguard-VPI-Insulation.html

I would say that as long as the water was fresh, not salt, and that it wasn't dirty or contaminated, and it didn't stay in the machine for very long (wasn't allowed to evaporate), and the insulation was clean and not too old and hadn't been subjected to a lot of high temperature operation, it shouldn't be too bad.

The usual steps of using heated, forced air through the windings should be used to help dry out the machine, for an appropriate length of time (a few days would likely be better than a few hours or just one or two days). A PI (Polarization Index) can be run before and during the drying to monitor insulation condition during the drying process. (There's lots of information on PI tests; just use a good meggar. A hand-cranked meggar is usually best, but a good quality meggar used properly is also good--be sure to use at least 500 VDC for each measurement (presuming the machine windings are rated for 500 VDC).

If there's real serious concern, then a generator service firm can be contacted to do more testing using various methods (hi-potential testing; etc.)--but some of these can be destructive, but then better to find problem(s) with testing than when synchronized, right?

Hope this helps! The conditions (type of water; length of time "immersed"; condition of machine before "immersion"; etc.) all contribute to the way the machine should be dried and tested before being returned to service.

It's presumed the rotor didn't get wet.
 
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