Re: Secondary design help
> Original Poster: "Mark Broker" <broker-at-uwplatt.edu>
It sound like a very nice coil. At 22 awg, your looking at about 1,050 turns.
Your not way out in no mans land or anything like that. I think it would work
fine and should pull out some long arcs somewhere between 65 and 90 inches.
There have been a lot of great coils built with all types of forms, including
PVC. The trick is preparation for the form type your using and to stay away
from conductive fillers like carbon. They must be dried and sealed as they do
absorb moisture. I used a sono-tube form myself, but preparation was "not"
compremised. It has held up through all kinds of humidty/dry/freezing (really
freezing) conditions as well as a lot of fun. The PE form is ideal of course
and I would recommend it if you can get it in the size your looking for.
The toroid of 60pF seems a bit steep for this coil and sadly, it may actually
be my web page that recommended this. I did throw up a "coil design" thingy a
long time ago, upgraded it here and there, but haven't touched it in a long
time. I do remember recommending toroid sizes for input power. It still seems
too big for your coil (to me). I think 35pF is a better choice, and little
bigger than your 6" x 24" - BUT, at higher power levels, things may change and
maybe your coil could drive a larger toroid than that. I haven't reviewed that
area of my page in a long time - as matter of fact, I've been wanting to take
that entire design page down - I never liked it and couldn't find the right
format or words. I would much rather just throw up my own specs, talk about
theory, and leave the design notes to the experience of this Tesla List. As a
matter of fact, it's coming down this week (thanks for making me think about
this). I woulnd't worry much about the toroid, they are easy to throw together
for the purpose of experimenting with what size to use.
> So far, my design consists of a 1.8kVA input (dual 15/60 NSTs) with an
> LTR-style MMC (56nF). My primary is .50" copper tube spaced .50." I'm
> working on a SRSG at 120 BPS. I'd like to use a 6.27" OD, 6.07" ID x ~30"
> PVC secondary with 22AWG wire.
> The only areas that I'm still trying to investigate are the secondary
> design and the topload. First, I've read that PVC doesn't make a very good
> form due to its high RF losses. Secondly, I'm concerned that 22 AWG is too
> small, and that I should use 20 or 18 AWG. Finally, I'm also concerned
> that the topload is too small ("Top loads can NEVER be too big"). I've
> thrown a 6"x 24" toroid into WinTesla, with a capacitance of 32pF. I've
> seen on one Web page that the recommended toroid size for a 6" coil is
> 8"x40" (60pF) (in conjunction with an anit-corona ring, which I may add
> after I get it built and working well).
> So, my questions are:
> 1: Will I gain much by using a PE (or similar) form over a PVC form?
> 2: Is 22AWG wire OK on a 6" coil running at 1.8kVA?
> 3: Is my topload of 6x24" too small for my coil? (I DO intent to make
> a couple, but I'd like an idea of where to shoot for)