[Prev][Next][Index][Thread]

Re: Best Secondary Surface coating




From: 	Vivian[SMTP:V.C.Watts-at-btinternet-dot-com]
Reply To: 	Vivian
Sent: 	Thursday, November 20, 1997 1:26 PM
To: 	Tesla List
Subject: 	Re: Best Secondary Surface coating

Hi All,
Thanks for the response on the best surface coatings.  I have been doing a
little research.  The Epoxy Resin I was using  was designed for potting
electrical circuits.  But I didn't know the ratio's of coating to hardener
(I had acquired it as it was past if shelf date).  I used 1:1.  I have now
found it should have been 3:1 (so too much hardener).

I have examined the surface of the failed secondary under a microscope and
can see numerous small bubbles.  The trouble is I don't know if they were
their before I fired it up.  The appearance did change with time becoming a
little more milky but upon closer examination these are just bubbles.  No
evidence or arcing or where the shorted turns are though.  Its surprising on
closer inspection how much of a gap their is in what I thought was close
wound.  Calculations show I was packing at 95%.

The dielectric constant of the stuff I used was around 12Kv/mm.  From what I
can find Polyurethane is also around this figure.  The best it would seem is
conformal coatings at 90Kv/mm which beats anti Corona Lacquer at 48Kv/mm.

Jeff Parisse info from the list "Red 601" insulating varnish translated to
84Kv/mm.

My original secondary was 4.25" * 20" close wound.  My new one is 6.25" *
23.5" double space.  It will give a little more inductance.  I have coated
it with Insulating Varnish but it needs a lot more.  Question is I have run
out of varnish but I do have a lot of this Epoxy resin left.  Mmm Maybe I'll
sleep on it.

Viv Watts UK.