[Johnson] Transformer "cooking"

[Roy Morgan]

On Jan 6, 2014, at 3:14 PM, Carl <km1h at jeremy.mv.com> wrote:

> I dont know if Measures used the method I described decades ago but there are methods that work.
> ...
> Short the secondary with an ampmeter and fuse in series. Place a Variac on the primary with another ampmeter and fuse. ...
> Bring up the Variac very slowly while monitoring both meters. ...
> It might take days or even weeks until it is running at even half its CCS KVA rating;

I assume you mean the CURRENTS that would be seen if it were running normally under full load.

> consider the electric bill vs saving money on a new transformer.
> 
> The last one I recovered was ... a 275# monster ...
> 
> It took a week of cooking out in the garage, at up to around 75% of calculated KVA, ... followed by a dunking in a vat of transformer varnish after a hi pot at 13.5KV which was the limit of my tester.

 Again, I assume you mean the primary and/or secondarily CURRENTS that would be expected in normal operation.

I’ll check my garage for a vat of transformer varnish. heheh  

I’m pretty sure I don’t have a variac the right size for a 275 pound transformer, but:  How about using a lower voltage transformer such as a monster filament transformer, to feed the patient being warmed?  I wonder what sort of voltage the primary of your monster took during the warming process.

Thanks much for your post.  It gets added to my transformer notes file.

Roy

Roy Morgan
RoyMorgan at alum.mit.edu
K1LKY Since 1958 - Keep 'em Glowing!