Jumping in with both feet?
From: D.C. Cox [SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Friday, January 30, 1998 12:49 AM
To: Tesla List
Subject: Re: Jumping in with both feet?
As the top load increases the sec freq drops down which requires either
more inductance or more capacitance. If more capacitance is added greater
drive current is required to quickly recharge the cap. Drive current is
usually much more important than potential assuming you are running in the
area of 10-15 kV. Even with smaller coils usually adding another xmfr in
parallel and --- if quenching is efficient --- the output increases
dramatically. Adding more capacitance in the primary as the top load
increases adds much more energy in the system which --- hopefully with
proper coupling and efficient quenching --- provides a lot more energy in
the secondary inductor. With sec inductors above 4-6 inch diameter the
preferred method of providing effective coupling in the 0.18 to 0.22 range
is to use a flat spiral with the innermost turn approx 1 1/2 to 2 inches
away from the sec coilform. The bottom of the sec winding should usually
be approx 1 inch above a straight line drawn horizontally across the top of
the primary inductor. If your sec outputs become large you might also
consider adding a ground "strike rail", ie, a copper wire suspended
slightly above and 2 inches outside of the primary inductor. Make it a 7/8
turn coil -- not a completed turn which will act as a short -- and hook it
to ground. This will catch any stray sparks before they curve back into
the primary --- or worse yet --- the sec. coil where they will instantly
Hope this helps out.
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-pupman-dot-com>
> Subject: Jumping in with both feet?
> Date: Thursday, January 29, 1998 10:20 PM
> From: SBJohnston-at-aol-dot-com [SMTP:SBJohnston-at-aol-dot-com]
> Sent: Thursday, January 29, 1998 12:36 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: Jumping in with both feet?
> D.C. Cox wrote:
> >One problem -- you are overcoupled. Your primary should be
> > in a flat expanding spiral for the primary not 2/3 the way
> >up the sec coil. This will also lead to flashovers from
> >primary to sec coil which may damage the magnet wire.
> The primary is not 2/3 the way up the secondary... the cold end of the
> secondary sticks 2/3 of the way into the primary. The coils are spaced
> least 5-1/2" apart all the way around, and it is the cold end of the
> I'm not sure I understand the advantage of a flat sprial primary -- can
> >You may also want to switch to a larger top electrode
> >such as a 20 x 5 inch toroid for better electrostatic control
> >and higher output potential. Drive current necessary is
> >120-150 ma at 10-12 kV for this type of performance.
> If I wish to add a toroidal top-load/discharge terminal i can see it will
> shift the resonance of the secondary, but why will it required greater
> Thanks for the info!
> Steve Johnston