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

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

Original poster: "Edward Wingate by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ewing7-at-rochester.rr-dot-com>

Tesla list wrote:
> 
> Original poster: "Dave Hartwick by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>
> 
> 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

Dave,

If you need multiple coats of varnish to build up a thick layer of
insulating material to suppress corona or racing arcs, your coil is
either not designed properly, tuned properly, or both. I use a couple
coats of old fashioned shellac for no reason other than to hold the
wire in place.

A thick coating would be desirable on a coil that is torn down and
transported frequently to protect the windings from physical damage.

Ed Wingate RATCB