[AMPS] Stupid transformer question

2 2@vc.net
Sun, 16 Dec 2001 05:38:44 -0800

>> A quick&dirty test of the insulation might be to simply connect the
>> (fused) unloaded xfmr's primary to 220 briefly to see if it can stand
>> twice the voltage it will see when you actually use it. Then lift the
>> secondary winding from ground, ground the other end and re-test to
>> verify the insulation at both ends.
>Woah there! Don't do that!
>Most efficient transformers are designed to run with the core near 
>saturation. Very few would have safety factor of 2x.
> ... ...
//   Most of the transformers I've tested begin to saturate at c. 20% 
overvoltage.  100% overvoltage is unreasonable.  The best insulation test 
is with a high-pot tester.  
-  To see when the core is getting near saturation, unload the 
secondaries, slowly increase primary potential and watch primary current. 
 When pri. current begins to increase substantially, saturation is 
-  To improve transformer insulation, pot the transformer with 
(polyester) fiberglass laminating resin.  Potting can be done in one's 
workshop for low cost.  Info on insulation/potting is on my my Web site.  
 See "Amplifiers" - Part 3. 


-  R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.  

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