Carrier chiller: medium voltage motor and corona effect

[evapcoil]

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Hello Colleagues
I am working on Carrier 19XR equipped with medium voltage motors (6.6KV).
Unfortunately, on 12 machines installed 5 of them have already failed because of grounding of the elctrical motors, and recently We opened other three machines and all three are showing signs of Corona phenomen on their stators in different degrees of severity.
See attached pictures for reference.
Has anybody dealt with this problem before? If so , what was the cause of it and how did you solve it?

Thank you all for any feedback and/or suggestion.

[install monkey]

http://electricalnotes.wordpress.com...corona-effect/
or even better
http://docs.lib.purdue.edu/cgi/viewc...3&context=icec

[evapcoil]

Thank you Monkey for the links, very useful, I had also found few similar links and they explain pretty well what the effect is, but I was hoping for more "first hands" comments.

[evapcoil]

Anybody? :-(

[Magoo]

6.6Kv 6600 volts and moisture has got be super scary. 19XR are they 134a, dirty systems, leaks, moisture. Zap factor. And you are in a steel ship in water, extra scary scenario.
With the humidity problem, put a bucket of fresh water after the heating coil, and fill it regularly, not rocket science.
regards magoo

[evapcoil]

On another ship We had 11Kv chillers.. ;-)
I will keep in mind the suggestion for the humidity problem..