RE: Designing BIG Secondary Coil

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

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