Re: Ballasting a Pole Pig

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Original poster: Ed Phillips <evp@xxxxxxxxxxx>


I never thought of putting them in parallel.  If there is a 100V 
difference in the output voltage of each transformer, for example 1 
NST is 15.1KV while a second might be 14.9KV would they get stressed 
that way if placed in parallel? Or does a 100 volt not much to an NST?"

   The leakage reactance of a 15 kV, 30 ma transformer is of the 
order of 500 k (15000/0.030).  The current flowing between two 
transformers with a difference of terminal voltage of 100 would be 
(100/1000000) or only 100 uA.  Parallel them happily.  I've hooked a 
12 kV and 15  kV 60 ma NST in parallel and had no 
problems.  Application wasn't TC but that shouldn't make any 
difference.  Short-circuit current was close to 120 ma and 
open-circuit voltage should be have been 13.5 kV but never measured it.

Ed