Re: New 4" coil: R.Hull and CSN, Secondary Varnish

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Dave,

At 03:02 PM 8/30/2002 -0400, you wrote:
>Guys,
>What is the current thinking on applying secondary insulation, in this case
>MinWax gloss polyurethane? There was a time when multiple coats to build a
>up a thick layer was desirable for  corona suppression, racing arcs, etc.
>Richard Quick was one such advocate.
>
>I note that Richard Hull advocates minimum or no varnish at all, stating
>that pretty secondaries with lots of varnish are also lossy. I've got about
>5 coats on the new 4" secondary (#26, 1500 turns) and am thinking that's
>enough, maybe too much. I've never done A B tests with identical secondaries
>that differ only in varnish quantity.
>
>I also wonder how Glyptal and other substabces compare in terms of
>lossiness.
>
>
>Generally regarding Rich Hull's work: I'm now reading his Guide to the
>Colorado Springs Notes--1993, 2nd edition 1995). Here he addresses the
>secondary insulation matter. He also concludes, for example, that cap size
>for a given transformer should be smaller than is generally advocated today.
>He says that a 5kVA 14.4 kV piglet won't handle a 0.06 ufd cap, that 0.005
>ufd is largest a 15/30 NST will power up. This is certainly at odds with
>more recent LTR methods.
>
>The overall question is what is still viable from work generated 8-10 years
>ago? And that goes for any theory that is some years old now. Certainly,
>much of his conclusions are still valid--Big toroids, magnifier theory.
>Dave Hartwick
>
>
>

I am not sure varnished vs. unvarnished secondary Q has ever been studied.
The varnish certainly is desirable in protecting the secondary, adding
"some" insulation value, and holding the windings in place.  Perhaps we can
get a few folks to measure the before and after Q of their secondaries.
Secondary Q is a big deal for my OLTC coil as I am finding out...  :-(


A 15/30 NST can fully charge a 0.0138uF cap at 120BPS in a sync gap LTR
system.  "The" chart is at:

http://hot-streamer-dot-com/temp/MMCcapSales.gif

	BTW - Many thanks to Mark Broker for making this chart.  Probably one of
the most used charts out there!

Saturating LTR systems "could" charge even far high value caps, but that
technology is in "our" future...

Richard's Hull's book was written long before the LTR principles were
understood and used.  Today, we take LTR coils for granted like they have
always been here. However, those technologies are only a few years old, so
any older work in those ares may be out of date.  Richard also talks of oil
filled poly caps.  Another technology that suddenly became obsolete in the
last few years.  Richard's 1995 work tells many great things, but it could
not tell the future ;-))  One reason there are no "new" books, is that a
book written 'this year' may be out of date 'next year'...  Things are
changing very fast...

Cheers,

	Terry