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Re: help with a different type of coil
From: Alfred A. Skrocki[SMTP:alfred.skrocki-at-cybernetworking-dot-com]
Reply To: alfred.skrocki-at-cybernetworking-dot-com
Sent: Friday, July 25, 1997 11:51 AM
To: Tesla List
Subject: Re: help with a different type of coil
On Wednesday, July 02, 1997 9:48 AM Rodney Davies
[SMTP:rgd872-at-anu.edu.au] wrote;
> > Right now, I'm trying to build a tesla coil, the thing is, it isn't like
> > any of the ones (as far as I can tell) that are discussed about in this
> > group or are frequently seen on the web. We used one in my Physics
> > class and my teacher said it was a tesla coil, but I didn't recognize it
> > as one. Well, it is rather old, but I will describe it. It has an
> > electromagnetic switch, that once it opens, it breaks its own circuit
> > (the power to the magnet) and thus closes again and this cycle repeats
> > very fast. The switch also breaks the current of a separate circuit
> > consisting of a power supply, a coil, and a spark gap. My teacher said
> > that breaking the circuit in the coil generates high voldages and the
> > sparks to jump the gap. The coil he used was powered by a low
> > voltage/current dc power supply. The coil is iron core, my teacher said
> > it is better for inductance. I'm not to clear on the inductance stuff.
> What you've described is an induction coil - another Tesla invention!
Rodney, Dr. Tesla invented many great things but the induction
coil was not one of them!
> It works similar to a tesla coil, but on DC. (yes, DC TC's do exist too!),
> but you should be able to slide the outer-coil off.
The operating priniple of an induction coil has NOTHING
WHAT-SO-EVER in common with a Tesla coil! An induction oil is
essentialy an open core transformer driven by pulsating DC from the
interuptor in it's primary circuit, it's ratio of transformation is
in direct relation to the primary to secondary turns ratio. A Tesla
coil operates by transfering energy between to differing capacitances
or indutances and its ratio of transformation is in relation to the
ratio of primary to secondary capacitance or inductance.
> Tesla coils *do not* have iron cores, so it _must_ be an induction coil as
> I know some do.
True Tesla coils do not have iron cores, BUT there are other
things besides induction coils that have iron cores. There is a very
simple device called a "kicker coil" that is nothing more than an
iron core inductor! The priniple of the kicker coil is based on
Michael Faraday's obseration that the faster a supply voltage is
broken from an inductor the higher the counter E.M.F. generated. This
by the way is why Dr. Tesla started out with mercury turbine
interuptors and eventualy went on to using the disruptive disharge of
a capacitor to drive the primary circuits of his High Frequency
coils.
Kevin's description of what his teacher demonstrated is rather
ambigious and it is difficult to determine if he is describing an
induction oil or a Tesla coil driven by a "kicker coil". The big
difference is that an induction coil has both a primary and a
secondary wound over the iron core while the "kicker coil" is just
one large winding over an iron core. The origional reason "kicker
coils" were used to drive some early amature Tesla coils was due to
the lack of an A.C. supply. It is also a very good substitute today
for the High voltage transformers we use , especialy for those who
can't get neon sign transformers or pole pigs. For the benefit of
those who may not be able to get H.V. transformers below is an ASCII
diagram of a "kicker coil" driven Tesla coil. BTW some of you may
recognize the ciruit is identical to that used in the hand held
vacuum testers and the old "Violet-Ray" machines.
___
(___)
)
)
)
)
) S
)
__________________)
VG ____ _|_ )
| | ___C )P
#( |__|__________)
C #( |
O #( |
I #( |
L #( |
| |
115V
AC or DC
The iron core coil is connected at one side of it's windings to
the line. The other side of the coil connects to a vibrating armature
identical to those found on the old induction coils. The stationary
contact of the interrupter is connected to a Tesla coil primary P,
the other side of the primary is connected to the Tesla coil
secondary S. The primary also connects to the moving contact of the
interrupter and there is a capacitor C across the vibrating spark gap
VG. There is an adjusting screw that pushes the moving armature of
the vibrating spark gap closer to or further away from the stationary
contact.
For those who want detailed instructions for building this kind
of Tesla coil look in Thomas Stanley Curtis's "High Frequency
Apparatus" 1916 (reprinted by Lindsay Publications 1988)in chapter
VIII "Kicking Coil Apparatus".
Sincerely
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Alfred A. Skrocki
alfred.skrocki-at-cybernetworking-dot-com
.ooo0 0ooo.
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