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Re: [Fwd: Spark gap not firing]

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

> At 400kHz, the high
> frequency voltage is just not going to get very far in the output windings
> and that high voltage my hit only a few layers and BLAMMO!  Since trying to
> figure out how the high frequency voltage distributes in the output winding
> of an NST is rather messy.  

	Analysis may be messy, but well within the capability of modern
analysis tools.  It would be very interesting if someone could simulate
what happens (in particular the voltage differentials between turns and

	I think careful post-mortem examinations of failed transformers should
yield information on exactly where the insulation failures occurred and
thus to a much better understanding of failure modes.  To perform the
exams one first needs failed transformers along with the circumstances
of their failures, and then dig into the bloody tar (very carefully) and
see what happened.  In this regard, the frequent reports of transformer
resurrection by melting the tar or "de-potting" makes me suspect failure
unrelated to inter-turn or inter-layer shorts.

> I figure it is best to simply stop it from ever
> going there...

	Absolutely no argument there!

> Reports like yours of NSTs taking this high frequency voltage are
> encouraging.  However, I suspect that is an exceptional case.  

	I'm not so sure, but it would sure be interesting to know!

> Since the
> strong emphasis on using protection filters, and putting the gap across the
> NST began, the number of NST failures has dropped dramatically...

	My question is as to the actual cause of the observed drop in failure
rates.  Could it be as simple as more careful attention to gap spacing,
or is it really the result of keeping high frequencies out of the
transformers?  In other words, given the effect what was the real cause
(of reduced transformer failures)?  Building adequate filters isn't as
easy as keeping the gap spacing down.  Does it really help?

> Cheers,
>         Terry