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Re: [Amps] questions on my tranformer test

Subject: Re: [Amps] questions on my tranformer test
From: David Kirkby <>
Date: Tue, 14 Jun 2005 07:53:17 +0100
List-post: <>
Will Matney wrote:
 > The only way you can tell for sure is find the wire size used
> in the coil. If you knew what the wire insulation was,
> so to know its temperature rating, you could snake a  
> thermostat wire down in the center of the winding 
 > and run it under load to
> see what the coils innards are heating to. Or do 
 > the hope-so test and see how hot the core and
 > coil gets by touch which isn't accurate. If its right
 > for the load, the core and coil should just be warm to the
> touch, and not close to hot enough as you couldn't keep 
> your hand on it. 180 degrees is way too hot for any to run. 
> Something in the order of 100 degrees to maybe 110 is about maximum 
> for one in open air.
> Best,
> Will


Can you not infer the average temperature rise by measures the DC 
resistance cold and then after some time the DC resistance when hot? The 
temperature coefficient of copper will give you the mean rise. If there 
are multiple taps, you should be able to find the mean rise on different 
bits of the transformer.

If the secondary is wound over the secondary, you could be pretty damn 
sure the primary would get hottest.

I guess you would need a pretty decent DVM (preferably with 4-wire 
resistance measurements) to do this on, but it might be practical. 
Although I have not sat down and worked out what the change in R will 
be, and so if its easily measurable.

your email client is sending one long line of text, with no line breaks. 
It's common to set a line break of about 72 characters. Some mail 
readers will have problems with a very long line. Hence I reformatted my 

David Kirkby,

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