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Sanity Check for me
----------
From: Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent: Tuesday, March 17, 1998 8:55 AM
To: Tesla List
Subject: Re: Sanity Check for me
Tesla List wrote:
>
> ----------
> From: baumann-at-proton.llumc.edu [SMTP:baumann-at-proton.llumc.edu]
> Sent: Monday, March 16, 1998 3:45 AM
> To: tesla-at-pupman-dot-com
> Subject: Sanity Check for me
>
> I have the opportunity to get a rather large diameter chunk of PVC,
> and am now dreaming of that monster coil. However, when I start running
> the numbers - I need a sanity check from some of you more familiar with
> this size beast:
>
> What I have the chance for is some 18" diameter PVC, in about 6ft
> sections. Leaving my sanity out of the question for the moment, i
> thought this would be a rather nice coilform.
>
> Then I started running numbers:
> If I use 18AWG wire, WinTesla tells me that at 44inches, I would
> have an unloaded frequency of about 77Khz, at an HD ratio of 2.35
> This is about 1000 turns and about 5000 ft of wire.
>
> If I use 22AWG still aiming for 1000 turns: ratio drops to 1.5 (27")
> and frequency to about 70Khz
>
> I would assume the 18AWG is required to keep the resistive losses
> down.
>
> Throw a 6"x36" toroid on there, and the frequencys drop to the
> 40khz range, and the cap size jumps from about 0.03 to 0.07 for 22awg
> and from 0.02 to 0.05 for the 18AWG, operating frequencies drop
> into the 40Khz range
>
> Primary would be close to 100ft of tubing if I used 1/4"
>
> Would I be wasting my time? And if so, is there a use for this
> large PVC that I don't see? [It's going in the trash unless I find
> a use..]
>
> --
> --
> Michael Baumann Optivus Technology Inc.|Loma Linda University Medical Center
> San Bernardino, California. (909)799-8308 |Internet: baumann-at-llumc.edu
Michael,
Big coils simply cost bigger bucks. However, this sounds like it would
make a dandy coil form! If you were serious, you should go with at least
#16 AWG space-wound or #14 AWG space-wound on at least a 5' length
coilform so that you end up with 500-600 turns. There's nothing magical
about 800 or 100 turns, and the added wire will add weight and cost. Go
with the larger wire diameter and use at least a 5' coilform, since this
coil should be able to handle significant power (20 KVA+). Assuming 600
turns of #14 AWG, and a winding length of 60", this will give you a
non-loaded secondary frequency of around 143 kHz, and would use about 35
pounds of wire.
Toroid diameter should be at least 48", and ROC should be commensurate
with the anticipated power level, but at least 8-10" to start with, and
12" if you drive it to higher power levels. Assuming a 60" x 8" toroid,
you'll get about around 45-50 pF of topload C when mounted atop your
coil. This will drop the loaded frequency down to about 90 kHz.
The primary should be constructed from 3/8" Cu tubing or,
preferentially, 1/2" material. Assuming a tank cap of 0.1 uF being
driven from a 10 KVA source (minimum), and 3" radial spacing between the
innermost primary turn and the secondary you'll only need about a 6-turn
primary to bring the system into tune at around 90 kHz at turn 5. You
should be able to use about 50 feet of material. The power source should
be a pole-pig, ballasted with one or two 200 A welders. The rotary gap
must be capable of handling large (~1000 Amp peak) primary currents.
1/8" TIG rod won't work here at least 1/4" or 3/8" should be used.
You'll also need to make a power control cabinet with at least two
ganged 240 Volt variacs. Much of the cost will be associated with power
control, gap, and tank cap. You can expect a coil this size to be at
least in the multi kilobuck range.
Other alternative uses:
A smaller, short-squat standard coil, operated at lower power levels. A
magnifier driver secondary coilform. A planter... :^)
Hope this ballparks some options for you, and safe coilin' to you,
Michael!
-- Bert --