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How do I make my HV chokes?
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From: Robert W. Stephens [SMTP:rwstephens-at-headwaters-dot-com]
Sent: Tuesday, February 24, 1998 3:27 PM
To: Tesla List
Subject: Re: How do I make my HV chokes?
> From: Rick Myers [SMTP:rcm-at-chile.cs.itc.hp-dot-com]
> Sent: Monday, February 23, 1998 5:59 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: How do I make my HV chokes?
<snippage>
Rick Myers wrote:
> One thing nobody has mentioned here is the need to prevent 60Hz resonance
> in the NST. This is probably what killed the above-mentioned transformer.
> The LRC network not only keeps RF from getting into the NST, it must
> also protect the NST from 60Hz resonance. Brent Turner has some good info
> on this in his book.
>
> Rick
Rick,
I have to disagree with you on this one. In order to get the most
performance from a neon transformer powered coil employing a fixed
static gap I believe that resonant operation at 60 Hz is required.
Since this causes very high potentials to appear in the neon
transformer secondary windings, one must rely entirely on proper
setting of the system sparkgap (don't go too big a spacing) and also
in the use of a safety gap across the transformer, as well as large
inductance protection chokes in series with the neon bushings, or your neon
will have an early demise. With the proper choice of choke
inductance you can still operate the transformer in 60Hz resonance
while reducing the voltage seen from each bushing to ground because
the voltage rise becomes disrributed between these components, each
then seeing less than the full amount. Superimposed RF kickback is
the other deadly component which is also dealt with to a good extent
with the large value series inductors IMO.
It is an interesting coincidence that most neon transformers, when
loaded with the optimium sized capacitance that they can efficiently
charge for TC use throws most of them into this 60Hz resonance
condition.
60 Hz resonant charging of the system cap is very much like running a
small 3 or 4 cylinder automobile engine with a turbocharger to make
it provide the level of performance as required. It has been done by the
automotive industry for years. One could argue that 4 cylinder
engines were never intended to drive full sized passenger cars (and
they'd be right), one could also argue (and they'd be right) that neon transformers
were never intended to power Tesla coils! : )
Oh, and just to vent a pet peeve about sloppy use of technical
terminology often found here on this list while on the subject. While I've
noted that all cars come with a 'tranny', I've yet to see a
commercial neon sign which contained one!
Robert W. Stephens
Director
Lindsay Scientific Co.
RR1 Shelburne, ON Canada L0N-1S5
Tel: 1-519-925-1771 Fax:
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