Re: Toroid connection (fwd)

---------- Forwarded message ----------
Date: Tue, 21 Apr 1998 06:33:56 -0500
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Toroid connection

Tesla List wrote:
> ----------
> From:  Dsurfr [SMTP:Dsurfr-at-aol-dot-com]
> Sent:  Monday, April 20, 1998 5:14 PM
> To:  tesla-at-pupman-dot-com
> Subject:  Toroid connection
> What is the proper way of connecting a toroid & is there a proper height above
> the secondary's top winding? I have a 4" ceramic stand-off insulator sitting
> on a 1/8" piece of plexi on the top of my secondary coil. I ran the wire from
> my top turn to a brass bolt in the top of the insulator to which I connected
> my toroid. I'm getting a lot of corona loss from the top windings & the
> connection. Should I lower the toroid / decrease the length of the connecting
> wire or is this normal? Also is this the correct way of connecting to the
> toroid? Thanks, Jim


It sounds like you have a relatively small toroid versus coil diameter
and you may also have excessive space between the top of the winding and
the toroid. Try lowering the toroid. Virtually anything can be used as a
spacer - I use 2" diameter PVC and pipe end-caps. The connecting wire
should loop around the toroid support with enough slack to easily
attach/detatch the wire to the toroid. The wire should not extend beyond
the radius of the coil. 

In addition to providing capacitance, the toroid provides critically
important electrostatic field shaping to prevent corona from the top of
your coil's winding. A properly sized toroid should be at least 2-3X the
coil diameter. The height is not very critical, but is usually not more
than [0.5 - 1.0 X coilform diameter] from the top of the winding to the
horizontal centerline of the toroid - larger diameter toroids can be
placed higher and still provide adequate shielding for the winding below
as well as greater distance to the primary and strikerail below. Less
distance provides better coilform shielding, and will only slightly
reduce the topload capacitance of the toroid.

Safe coilin' to you!

-- Bert --