[AMRadio] Drying iron

John Lawson jpl15 at panix.com
Sun Sep 18 12:34:07 EDT 2005

On Sun, 18 Sep 2005, John Lyles wrote:

> You could put a short on the secondary terminals, and run up the primary 
> voltage with a variac, to where you get the full current flowing in the 
> short.

  I second this, with a slight caveat - I've used this technique over the 
years for transformers and chokes that have been in damp places, out in 
the weather, (or in a few cases actually submerged) - however I terminate 
the secondaries in some appropriate resistance - sometimes various lamps 
work nicely for this - and then use a Variac on the primary, and use 
plenty of patience!

   If there's a lot of water, you have to take it very slow as it's sure to 
arc no matter what you do - this causes insulation damage and super-heated 
steam in the windings.

   But this is by far the best method, since it heats 'from the inside out' 
- all the major utilities use this when drying out Really Big Iron - even 
to dessicate the insulating oil.

   But I don't think I'd short the secondaries - this might tend to 
concentrate excessive currents at any 'weak spots'.


John  KB6SCO

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