Subject: Re: Transformers
From: Marcus Young <pxeyoung-at-dingo.cc.uq.oz.au>
Date: Thu, 08 Feb 1996 16:39:16 -0600
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>What is the best way to try to see if a transformer (pole or potential)
>is good using only a DVOM? Is it just a matter of making sure the
>terminals aren't open circuited, and that the LV and HV sides aren't
>shorted together (assuming they're really not electrically connected),
>or is there more to it than that?
Testing for opens and shorts would be good place to start allright! There
are however two other proplems which come to mind. If you dont know what
the resistance of the transformer windings is 'supposed'
to be, there is still the possibility that windings on some turns of
individual inductors might be shorted, which could cause havoc with voltage
The other problem is that a short caused by arching to the core ect, will
only show up when the transformer is under power.
I believe however that pole-pigs are usually taken out of service after X
amount of years, rather than waiting for them to fail in some way. It seems
most likley that a used 'pig' will still be in good working order....I think!??
You could apply a limited 60Hz power source accross the HV side and roughly
calculate the turns ratio from the output, though Ive only used this method with
small 'non-TC' transformers. I imagine that it will probably take much more
juice to saturate a big core sufficiently for any accurate measurement!
Perhaps power the HV side with a neon of the same voltage output as the HV
side of the pig and see if it steps the voltage back down to mains potential
properly. This will also reveal shorts which exist only under operational
Just taking a shot.....