[TCML] BPS Testing

[bartb]

Hi John,

I understand the type of tear-apart you did. If you leave out 
laminations, it will enter saturation with less current (at which point 
since the core cannot absorb any further, it saturates and current can 
then go very high). I expect saturation occurred earlier and then went 
into heavy currents (the transformer should have felt a little warm 
after running it if this was the case). The potting itself should not 
affect current (other than a heat dissipation variation), but 
laminations certainly would. Given that NST hv windings are so sensitive 
to over-voltage, it wouldn't surprise me if the core was also on the 
ragged edge by design.

Take care,
Bart


FutureT at aol.com wrote:
> Bart,
>  
> I have a Jefferson 15/60 NST that I unpotted.  I removed the outer  
> lamination frame
> from the straight core part to do a better job of cleaning it up.  The  outer 
> lamination
> frame can be slid off from the straight core, although it's difficult  to do. 
>  Then when I 
> reassembled it, I was not able to fit every thin lamination back in  place, 
> so I left a
> few out.  I did not remove any shunts because the only way to remove  them
> would be to cut a part off from each lamination.  When  I connected this NST 
> to
> my coil, it drew about 3500 VA.  I don't remember if I measured the  wattage
> or power factor.  I forget also what type of coil it was.  But in  any case
> the unpotting may have increased the power draw in this case.  I  
> unfortunately don't
> remember how the NST behaved before I unpotted it.  I was probably  feeding
> the NST 140 volts.  So the current draw was about 25 amps or  so.   If I 
> remember correctly, I was using a static gap.  Maybe just leaving out  a
> few laminations might increase the current draw substantially, if the  current
> draw did actually increase after unpotting.  Or maybe the unpotting  affected
> it by sliding the frame off the straight core.  Maybe the current draw  is 
> very 
> sensitive to all this.  I don't know.  Something to consider  though.  
>  
> John
>
>
>
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