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Re: Protecting a potential transformer
Hi Jay,
The current theory is that the very high inductance of NST secondaries
will induce high voltages in the outer layers of the secondary windings
when they get hit by high frequencies. Did you happen to notice that the
outer layers tend to fail while the inner layers of the secondary windings
remain in good shape? If so, that would tend to support this theory.
Cheers,
Terry
At 01:03 PM 05/15/2000 -0700, you wrote:
>Ted-
>
>In both cases when I blew up the 15/60 I had a dual safety gap from each HV
>terminal of the transformer to Gnd, and a series choke on each HV leg going
>to the spark gap. I think the chokes were about 4mH based on a crude
>measurement w/ a signal generator and an oscilloscope.
>The first time the xfmr failed, I think I had opened up the safety gap
>rather wide. It seemed to be limiting my performance and I got a little
>caught up in the quest for longer sparks... I also had a static gap which
>was not quenching well which also lead to a wider main gap opening to try to
>get better output.
>Since I had purchased the 15/60 new when I could not find a used one, I was
>able to return it to be replaced under warranty. By the time I got the
>replacement a week later, I had gone to an air blast gap which worked much
>better and allowed a main gap opening of closer to 1/4 inch rather than
>around 1/2 inch. I also adjusted the safety gaps just wide enough not to
>fire with only the transformer connected, and promised myself I would leave
>them there. At some point I also eliminated the chokes, but it resulted in
>much more frequent firing of the safety gap, so I put them back in. This
>worked for some time but the xfmr eventually failed again and I don't think
>the place I got it from is too likely to replace it under warranty again.
>
>Anyway, based on my experience, I think the RC filter and MOVs sound like a
>really good idea w/ NSTs.
>
>Jay
snip...
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