Re: Secondary design help
In a message dated 2/22/00 11:55:14 AM Pacific Standard Time,
<< Original Poster: "Mark Broker" <broker-at-uwplatt.edu>
I'm building my first "big" coil, and would like to make it as good as
possible without making too many mistakes.
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)
Unless you have access to a PE secondary coil form for cheap, I would use the
pvc form. The performance difference between the two would be very small. I
would clean, dry and seal the pvc form before winding wire on it. Also, be
sure to glue some solid 1.0" or so thick disks into the inside of the form.
One on each end a few inches inside from the ends and one in the center would
not hurt. This prevents sparks from traveling inside the form when you get
the hankering to crank up the power.
I think #22 wire is a good choice. That is what I use on my 6.0" dia
secondary running at 7 kva. My winding length is about 27.5" - I think 30"
would be fine.
The toroid size is as you know, power dependent. I started out with a 5" x
33" then built a 5" x 40". Now, with pole transformer, I use both toroids.