Generator Core Iron Problem

[wbd]

Hello,
We had an insulation failure on a hydro turbine generator. It was sent out for rewind and I am being told that the core iron is bad. They tested 3 times and still havve poor results. I am being told that the temperature is not stabilizing and this not uncommon for old generators with wavy iron. It is a 1905 generator.

1. What is meant by wavy iron?
2. I have a copy of the Stator Core Test sheet. Does anybody know of a primer or resource on what the tests are and how to interpet?

Thank you in advance for any and all replies.

 

[electricpete]

Here is an overview of core testing for motors. The principles are very similar for generators. The repair options for generators are somewhat different.

http://www.lexseco.com/Files/Lexseco_WhitePaper.pdf

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[edison123]

wbd

Unable to see your test sheet. In my opinion, that core is a centurion ready to be retired.

Those days they used hot-rolled magnetic sheets which had greater thickness variation than that of today's cold rolled sheets.

So, when you stack a core with a big bore, like hydro machines, you will see at the back of the core, the stacked core will appear wavy.

I would strongly recommend replacing the core with new cold rolled, non-grain oriented sheets, which have significantly lower losses.

* Women are like the police. They can have all the evidence in the world and yet they still want a confession - Chris Rock *

 

[burnt2x]

wbd,

I didn't have the luxury of handling century-old electrical equipment but a parallel experience looks the same as your present problem! I have the same problem with a motor that exhibited higher than normal no-load current drawn. We analyzed the problem and came to a conclusion that the culprit is the core of the stator. We had that motor core re-stacked and the problem was gone.

hope this helps.