Re: Designing BIG Secondary Coil

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

Original poster: "Brian by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ka1bbg-at-webryders-dot-net>

Hi, i picked a cake cover out of the dump today and said well that would
make a nice coil form. it is hard plastic but i am sure they must be cheap
compared to buying lexan, that might be something to look for. ole
tupperware surely wont do the job. cul brian f.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, September 06, 2002 10:15 AM
Subject: RE: Designing BIG Secondary Coil


> Original poster: "Malcolm Watts by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
>
> Hi Dave,
>
> On 5 Sep 2002, at 19:28, Tesla list wrote:
>
> > 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.
>
> Re the wall thickness: the best secondary I have wound to date
> followed the guidelines for a spacewound coil and was wound on -
> gasp!- a 10" diameter piece of thickwall sewer pipe. It outperforms a
> closewound coil wound on a skeletal former wrapped with 1/8" thick
> HDPE sheet with a 17" diameter and closewound with wire that *didn't*
> meet the closewound guideline.
>     I met with complete failure winding a 12" coil onto sonotube, and
> that was with the tarred layer removed and the remains for the form
> varnished *and not pre-dried* :(  The measure unloaded Q of that
> coil, spacewound and all was a miserable 30 - 40. That coil went out
> in an annual solid waste collection.
>     The unloaded Q of the 10" sewer pipe coil (not pre-varnished BTW)
> was about 300.
>
> Regards,
> Malcolm
>
> > 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
> >
> >
> >
> >
> >
> >
> >
> >
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