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Re: Toroid Capacitance calculated without earth-distance?
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> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Toroid Capacitance calculated without earth-distance?
> Date: Friday, April 28, 2000 9:48 PM
>
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
> Hi Ruud,
>
> The closed form formula's you see are for a toroid in "free
space"
> without any grounded objects near by.
And, they are actually empirical approximations, but probably good to 5%,
which is good enough.
Someone may be able to use the
> electrostatic "images" method to come up with an equation for a toroid
above
> ground if they really try (such things make my brain hurt ;-)). I don't
know
> of anyone having done this?? Program's like E-Tesla5 take into account
the
> distance above ground and the distance to the ceiling and walls as well
as the
> primary coil.
To a zeroth order, I would expect that if the distance from the toroid to
ground is more than, say 2-3 toroid diameters (the big diameter), it's not
going to have a huge effect. Since in most TC's the toroid diameter is
less than half the height of the secondary, which usually doesn't sit right
on the ground anyway, the free space approximation is probably pretty
close.
>
> Of course, it can be argued that the toroid equations are not accurate
enough
> to notice if the ground is there or not ;-) You can use with E-Tesla5 to
do a
> sensitivity analysis if you are really bored ;-))
>