RE: Oil insulated secondaries (fwd) (Are they worth it?) (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 13 Sep 2007 09:11:57 -0400
From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: Oil insulated secondaries (fwd) (Are they worth it?) (fwd)


Scott,
     There is a type of epoxy made especially for coating stuff called
enviro-tex (or something of that nature).  It would probably work well for
coating secondaries, and it out gasses easily and completely in the
presence of CO2.  I use it for plasma globe stuff, but you may find it
worthwhile to get some and use compressed CO2 to out gass it on your
secondaries.  I hope this helps. Scott Bogard.

> Date: Wed, 12 Sep 2007 16:49:11 -0600
> From: tesla@xxxxxxxxxx
> To: tesla@xxxxxxxxxx
> Subject: Re: Oil insulated secondaries (fwd) (Are they worth it?) (fwd)
> 
> 
> ---------- Forwarded message ----------
> Date: Wed, 12 Sep 2007 08:05:46 -0700
> From: huil888 <huil888@xxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: Oil insulated secondaries (fwd) (Are they worth it?) (fwd)
> 
> Aaron -
> 
> I probably should have been more specific ........ the "pinhole with corona" 
> was present only on one of my first epoxy-coated secondary's, and that 
> subsequent refinements to the coating process essentially eliminated 
> pinholes.
> After initial testing of the coil revealed the presence of the pit in the 
> coating, the defect was repaired using a toothpick to apply a tiny droplet 
> of epoxy to fill the pit. That ended all corona discharge from the pit, and 
> the secondary ran corona-free thereafter.
> 
> During the last stages of the epoxy coating process, the secondary is 
> turning very slowly on the winding/coating jig, and every inch of the 
> surface can closely inspected for any thin spots or bubbles. Bubbles are 
> "popped" using a hot air gun to locally heat the epoxy, causing it to become 
> less viscous and the bubble to expand, which causes the bubble to pop or 
> collapse. In the coil that exhibited corona, there was not a real bubble of 
> trapped air in the coating, but a "pit" where a bubble had popped but the 
> epoxy had not flowed back into the pit. Also, when coating larger coils 
> where more than 2 pints of epoxy are used, I vacuum-degas the epoxy after 
> mixing. Even a small vane-type vacuum pump/compressor (like used with an 
> airbrush) will pull enough vacuum to effectively degas the epoxy, although 
> it will froth up to 2X or 3X its initial volume as the bubbles initially 
> expand. If you are very careful while applying the epoxy to the coil, very 
> few additional bubbles will be generated.
> 
> I should have clearly stated that the pinhole/corona was present on only one 
> secondary, and that it was repaired as soon as it was detected. It wouldn't 
> make much sense to go through the effort to epoxy coat the secondary, and 
> then leave a near-microscopic but easily repaired defect that would affect 
> the reliability of the coil.
> 
> Regards,
> Scott
> 
> ----- Original Message ----- 
> From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Tuesday, September 11, 2007 12:36 PM
> Subject: Re: Oil insulated secondaries (fwd) (Are they worth it?) (fwd)
> 
> 
> >
> > ---------- Forwarded message ----------
> > Date: Tue, 11 Sep 2007 09:19:20 -0700 (PDT)
> > From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
> > To: Tesla list <tesla@xxxxxxxxxx>
> > Subject: Re: Oil insulated secondaries (fwd) (Are they worth it?) (fwd)
> >
> > I don't doubt that an epoxy coating can provide some
> > measure of corona suppression, but the fact that you
> > get corona in the air bubbles does not strike me as
> > especially compelling evidence of its insulating
> > qualities.  No matter what you paint, coat, or wrap
> > your coil in, if you miss a spot, that spot seems much
> > more likely to suffer corona breakout.  In fact, it
> > seems reasonable (to me) to suggest that, by coating
> > your coil, you are in fact increasing the likelihood
> > that corona (e.g., in an air bubble) will cause
> > damage, because it will be concentrated in a few spots
> > versus distributed, as it would otherwise have been.
> >
> > Also, as I indicated below, there are plenty of
> > opportunities in Tesla coil design to avoid the
> > requirement of extreme insulation of your secondary
> > (e.g., oil immersion).  Most of these have become
> > well-known "rules of thumb" by now.  Unless you have
> > gone out of your way to disregard these rules of
> > thumb, leaving only an epoxy coating to save you, it
> > seems unreasonable to hold the success of your own
> > coils up as evidence that epoxy coating is a good
> > insulator.  Much more likely, in my opinion, is that
> > your design side-stepped the need for extreme
> > secondary insulation, either consciously, or by
> > application of what has come to be known as "common
> > sense" in coil design.
> >
> > Cheers,
> > Aaron, N7OE
> >
> > --- Tesla list <tesla@xxxxxxxxxx> wrote:
> >
> >>
> >> ---------- Forwarded message ----------
> >> Date: Mon, 10 Sep 2007 21:11:57 -0700
> >> From: huil888 <huil888@xxxxxxxxxxxx>
> >> To: Tesla list <tesla@xxxxxxxxxx>
> >> Subject: Re: Oil insulated secondaries (fwd) (Are
> >> they worth it?) (fwd)
> >>
> >> Aaron -
> >>
> >> I've got to disagree with your position that epoxy
> >> coatings don't provide
> >> effective electrical insulation. I've been using
> >> epoxy to coat every
> >> secondary I've wound over the last 8 years or so,
> >> and I can assure you that
> >> a heavy (.050" or thicker) epoxy coating provides
> >> extremely effective
> >> electrical insulation, as well as providing the
> >> mechanical protection you
> >> mention.
> >>
> >> Since I started using epoxy coatings, I have never
> >> had a secondary damaged
> >> by external arcing or flashover, even when used with
> >>  helical primaries with
> >> very high coupling factors. Exactly how much
> >> electrical insulation is
> >> provided can be seen when there is a tiny pinhole or
> >> near-microscopic bubble
> >> in the coating anywhere in the upper 1/2 of the
> >> secondary. Once the coil is
> >> tuned and operating at near peak power, corona and
> >> thin spidery arcs will
> >> flow out of the pinhole like a leak in a pressurized
> >> garden hose.
> >>
> >> I fully agree that aside from the novelty factor,
> >> its hard to justify the
> >> additional complexity and probability oil seepage
> >> with an oil-insulated
> >> secondary for a conventional Tesla coil.. A
> >> correctly applied epoxy coating
> >> will give the appearance that the secondary is
> >> encased in a perfect glass
> >> sleeve, an effect that you just can't get with
> >> concentric acrylic tubes with
> >> oil in between.
> >>
> >> The only place that I can think of where this
> >> additional complexity is
> >> likely to provide any real benefits is in a
> >> magnifier setup, where the
> >> extremely tight pri-sec coupling makes it very hard
> >> to prevent corona and
> >> flashover.
> >>
> >> Regards,
> >> Scott Hanson
> >>
> >>
> >>
> >> ----- Original Message ----- 
> >> From: "Tesla list" <tesla@xxxxxxxxxx>
> >> To: <tesla@xxxxxxxxxx>
> >> Sent: Monday, September 10, 2007 7:37 PM
> >> Subject: Re: Oil insulated secondaries (fwd) (Are
> >> they worth it?) (fwd)
> >>
> >>
> >> >
> >> > ---------- Forwarded message ----------
> >> > Date: Mon, 10 Sep 2007 09:53:09 -0700 (PDT)
> >> > From: J. Aaron Holmes
> >> <jaholmes@xxxxxxxxxxxxxxxxxx>
> >> > To: Tesla list <tesla@xxxxxxxxxx>
> >> > Subject: Re: Oil insulated secondaries (fwd) (Are
> >> they worth it?)
> >> >
> >> > Epoxy coating is not about electrically
> >> insulating,
> >> > it's about physically protecting and preventing
> >> the
> >> > windings from sliding off.  That's it, really.
> >> Oil
> >> > does neither of these things, and is instead all
> >> about
> >> > electrical insulation.  HOWEVER, whether it's any
> >> > advantage at all depends on what other aspects of
> >> your
> >> > design you hold constant, and given that most of
> >> these
> >> > other aspects are usually controllable in such a
> >> way
> >> > as to avoid the necessity of oil insulation, I'd
> >> have
> >> > to agree that oil insulated secondaries are
> >> moderately
> >> > to extremely silly in most cases.  They are
> >> > undoubtedly "interesting" and "cool", though.  I
> >> loved
> >> > the look of Terry Blake's coil, and decided to add
> >> my
> >> > own twist".
> >> >
> >> > All else being equal, I'd expect oil insulation
> >> would
> >> > make the secondary less susceptible to secondary
> >> > breakout, primary-secondary strikes, racing arcs,
> >> and
> >> > internal arcing.  This, in turn, might permit the
> >> use
> >> > of higher-than-average coupling, larger toploads
> >> > (which would otherwise tend to encourage secondary
> >> > breakout), and generally a bit more power,
> >> achieving a
> >> > higher-than-average streamer-to-secondary length
> >> > ratio.  But we'll see!!  Again, I doubt if it's a
> >> very
> >> > practical way to accomplish these things, but it
> >> is
> >> > nonetheless a fun twist.
> >> >
> >> > Cheers,
> >> > Aaron, N7OE
> >> >
> >> > --- Tesla list <tesla@xxxxxxxxxx> wrote:
> >> >
> >> >>
> >> >> ---------- Forwarded message ----------
> >> >> Date: Sun, 9 Sep 2007 18:22:33 -0700 (PDT)
> >> >> From: Yurtle Turtle <yurtle_t@xxxxxxxxx>
> >> >> To: Tesla list <tesla@xxxxxxxxxx>
> >> >> Subject: Re: Oil insulated secondaries (fwd)
> >> >>
> >> >> I'm just curious why oil would be better than
> >> simply
> >> >> potting it in epoxy. I realize it would look
> >> cooler.
> >> >> Seems like an oil tight seal would be harder to
> >> >> accomplish than one that only needs to hold up
> >> until
> >> >> the epoxy hardens.
> >> >>
> >> >> Adam
> >> >>
> >> >> --- Tesla list <tesla@xxxxxxxxxx> wrote:
> >> >>
> >> >> >
> >> >> > ---------- Forwarded message ----------
> >> >> > Date: Sat, 8 Sep 2007 16:22:58 -0700 (PDT)
> >> >> > From: J. Aaron Holmes
> >> >> <jaholmes@xxxxxxxxxxxxxxxxxx>
> >> >> > To: Tesla list <tesla@xxxxxxxxxx>
> >> >> > Subject: Re: Oil insulated secondaries (fwd)
> >> >> >
> >> >> > Hey there, Dave!  I'd be interested in any tips
> >> >> > here,
> >> >> > too, however I suspect the number of amateur
> >> >> coilers
> >> >> > who have built oil-insulated secondaries can be
> >> >> > counted on one hand, maybe less ;-)  The only
> >> >> > functioning amateur oil-insulated coil I've
> >> ever
> >> >> > seen
> >> >> > pictures of is Terry Blake's:
> >> >> >
> >> >>
> >> >
> >>
> > http://www.tb3.com/tesla/teslathon2003/tb_tc/tb_tc.htm
> >> >> >
> >> >> > It was his coil that inspired me to start
> >> building
> >> >> > my
> >> >> > own oil-insulated coil.
> >> >> >
> >> >> > I've also heard of a few oil-insulated research
> >> >> > coils,
> >> >> > and seen drawings illustrating their
> >> construction.
> >> >> >
> >> >> > For about the last year, I've been slowly
> >> >> gathering
> >> >> > the pieces for a medium-sized oil-filled
> >> >> secondary.
> >> >> > For lack of any real guidance on oil-insulated
> >> >> > construction, I've decided to strike out in
> >> what
> >> >> > seems
> >> >> > like a new direction:  I'm building the
> >> secondary
> >> >> > inside an oil-tight ceramic insulator that used
> >> to
> >> >> > house a 115kV capacitor:
> >> >> > http://silicon-arcana.com/cap/cap.jpg
> >> >> > (on left)
> >> >> >
> >> >> > It's about 4' tall and will accomodate a 6" x
> >> 30"
> >> >> > coil
> >> >> > form quite nicely.
> >>
> > === message truncated ===
> >
> >
> >
> > 
> 
> 
> 

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