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Re: Top Toroid
At 09:10 PM 1/29/97 -0700, you wrote:
>Subscriber: c604313-at-showme.missouri.edu Wed Jan 29 20:57:23 1997
>Date: Wed, 29 Jan 1997 13:33:57 -0600 (CST)
>From: c604313-at-showme.missouri.edu
>To: tesla-at-pupman-dot-com
>Cc: Tesla-list-subscribers-at-poodle.pupman-dot-com
>Subject: Re: Top Toroid
>
>
> Jeff,
> Here is a small list of Toroids and there capacitance in picofarads:
>
> Toroid (height X diameter) Picofarads
>
> 3 X 12 12.95
> 5 X 14 16.08
> 5 X 20 21.58
> 7 X 30 32.17
> 6 X 36 37.18
> 12 X 36 40.84
> 8 X 48 49.58
> 12 X 48 51.79
> 12 X 60 63.32
> 20 X 60 68.07
>
>
> The Toroid is measured in inches.
> One quick remark. try to construct the cap with the least amount of
>metal just a thin shell of metal is best (aluminum duct tape on 4 pvc
>joints fitted together works well) The reason being is that the top cap is
>also in the midst of the magnetic field that is set up by the primary ind.
>If the terminal cap was a solid chunk of metal, the changing magnetic
>field would set up an E field in the cap and induce current flow causing
>heating of the Terminal cap which is a waste of energy. you don't want the
>toroid to soak up the energy of the magnetic field you want that energy to
>be soaked up by your secondary coil.
> There is a good toroid home brew description on Bill Beaty's Tesla
>web page.
> enjoy!
> --Bert S.
>
>
>
Bert,
I trust these are calculated values!!! I can almost tell due to the fact
they are all in error from real world, honest to God, measured values. A
true, relative isolated toroid is usually about 25-30% lower in capacity
than the calcs say it is. My 12X3 spun unit is 7.8pf and my 5X20 is 15.1
pf. put them on a coil and they can appear to be even more than calculated!
It's a crap shoot! The thrust is that the math isn't even close for any
form of critical engineering purposes. Especially on small toroids.
Richard Hull, TCBOR