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Re: [TCML] BPS Testing

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,

FutureT@xxxxxxx wrote:
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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