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Tesla coil primary power


 JL> Hi All,
 JL> I'm up to the "primary supply" of my tesla coil and i need
 JL> (some more :) advice ...

 JL> I'm hoping to use a TV Flyback transformer to supply about 80,000V 
 JL> to the tesla primary coil (rather than use a more expensive
 JL> neon-transformer) ...

If you want to go cheap, and you do not want to use neons, then you
should consider powering the coil a with normal induction coil. In the
'states' a model T Ford spark coil can be bought new from JC Whitney.
But I think you would want to perhaps use a cheaper and more available
automovtive ignition coil. The ignition coil, like any induction coil,
will have to be pulsed. This can be done several ways. Some low fre-
quency solid state audio oscillator could be used as a trigger, an 
electro-mechanical vibrating switch could be used (like the guts from
a doorbell), or one end of the core could be exposed and a magnetic 
switch could be linked to the core field. These are just a few ideas.

 JL> 3) I can use a Walton-Cockcroft Voltage Multiplier circuit to boost
 JL> the voltage  (instead of a flyback), so I can acheive much higher
 JL> through-currents. Is there any way that I can convert the DC-Out of
 JL> the multiplier to AC (to drive the primary coil), or is there already
 JL> enough ripple in the multiplier output to drive the coil??

Tesla coils will run as well off DC as well as they run off AC. To make
a note, the HV induction coil output I described is a pulsed DC current. 
The power supply frequency, or lack of, is unimportant to the Tesla tank 
circuit. All you need is some way to reliably charge the Tesla tank cir- 
cuit capacitor with high enough voltage that the spark gap breaks down.
Once the gap breaks down the Tesla Tank circuit fires as an LC oscillator
whose frequency is completely independant of the power supply.

But re-reading your posts over a couple of times I get the feeling you
are thinking about having the power supply directly energize the primary.
This will work, but the power supply must consist of an oscillator that
will drive either the primary or secondary coil at the resonant frequency
of the secondary. The Tesla Tank circuit is such an oscillator. The pri-
mary coil is the inductance ( L ) and the tank circuit capacitor is of
course the capacitance ( C ). The spark gap is the switch, and performs
the function of a tube, or solid state device, in a more modern LC 
oscillator. 

 JL> 4) Does anyone have any other suggestions as to how I can construct 
 JL> a reliable primary??

This depends on the anticipated size of the resonate secondary coil to
be coupled with it. How big of a secondary coil are you planning to wind?
Usually I wind the primary as an inverted conical section, shaped much
like a "saucer". I figure the diameter of the inside turn about 5 cm 
larger that the diameter of the secondary coil it is to be used with.
I generally make up the primary of soft copper water pipe or refrig-
erator tubing about 1/4 - 3/4 of an inch in diameter at this power level,
and wind on about 15 turns total to make up this coil.


Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12