Re: Designing BIG Secondary Coil

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

Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


Dave

If you are building a large coil remember the most important effect on your
pocket book --- the cost of a lot of hi-Q factor energy discharge caps.
Most builders forget this factor and then discover they may have to dish out
$500 to $1000 to come up with the pri capacitance necessary to run the
monster.

We can supply coilforms of a special "glasserized" short fiber fiberglass
which is what we use on our larger coils but price is around $200-$350 per
coilform.  Sonotubes work fine. We used one on an earlier coil with 24 in
dia. sonotube and a 12 ft spark output.  It might be a bit lossy but the
electrons didn't seem to know the difference in the output spark.

Dr. Resonance




----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, September 05, 2002 6:28 PM
Subject: RE: Designing BIG Secondary Coil


> Original poster: "Dave Hartwick by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>
>
> Malcom,
> Fascinating recommendations. With a confined Lab, I've been thinking small
> dia secondaries, but this really makes no sense. The vertical height is
the
> problem. Why not go with large diameters?
> Of course, there is a minimum vertical height limitation, lest excessive
> striking of the strike rail become a problem.
>
> A suitable form for such large dia secs is always a problem. I think the
PVC
> tubing I've seen at the 12" mark has distressingly large wall thickness,
but
> is this a real world issue? Lexan or Plexi is out of the question for $$
> reasons. Sonotube is known to inflict low Q, though it has been used on
very
> large coils.
>
> I've thought of building a collapsible form, finishing the windings with
> epoxy, collapsing and removing the form, then inserting a modest High-Q
> structure internally for structural support.
>
> There are various tanks, trash buckets, made of HDPE, etc, that could be
> used.
>
>
> Dave Hartwick
>
>
>
>
> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <m.j.watts-at-massey.ac.nz>
>
> Hi Dan,
>
> On 5 Sep 2002, at 7:15, Tesla list wrote:
>
> > Original poster: "Mccauley, Daniel H by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
> >
> >
> >
> > I'm planning on building a relatively large secondary coil and primary
> > set-up which will be the basis for my future (high power 3kVA + ) coils.
> >
> > What should be my primary concerns for a large secondary when i do my
> > design.
> > Right now I have an enormous spool of 20AWG wire and I was planning on
> using
> > an 8" or 12" sonoform as my coilform.
> >
> > What should be my primary concerns for designing something this size.  I
> > guess i want to shoot for a frequency around 100kHz?  (with a proper
> toroid
> > of course)  Aspect ratio of around 4.5 or 5???  Anything else????
> >
> > Thanks
> > Dan
>
> Personally I'd go for the 12" coilform. Re wire size, I have two
> guidelines:
> (1) spacewound coil: the wire should have a minimum diameter of 3
> skin depths (so it could be bigger if you want) at the *lowest*
> frequency of operation (i.e. with the largest terminal you wish to use
> (2) closewound coil: the wire should have a minimum diameter of 5
> skin depths (and preferably more) for the same operating conditions.
>
> Both these guidelines will ensure that the secondary Q is high.
>
> Regards,
> Malcolm
>
>
>
>
>
>