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Re: [TCML] Is there an ideal frequency you should build around?

On 12/14/13 8:01 AM, shane bounds wrote:

Thanks Jim, I'll have to shorten the secondary up a bit from what I had
planned, (19" with around 950 turns on a 3.25 thin walled PVC tube with a
12x3 or 13x4 toroid).
Don't bother.. that's a fine form factor.. that 4-5:1 is a "guideline", it's not like going to 6:1 causes instant failure.
You might use one of the calculators (JavaTC for instance) to figure out, though, if you wind 800 turns it might work better).
Your 13x4 toroid is fine, and it's easy to make another one out of dryer duct and a piepan and stick it on and see if it makes a difference.
WHat are you using for a primary capacitor? That's usually the thing that drives the whole design, because certain values are easier to build/buy than others. The primary L is easy to adjust.. whether it winds up being 8 turns or 10 turns or 14 turns isn't a big deal. 




 But yeah this ones just a baby, if I can get 16" or

18" spark length I'll be impressed, then maybe someday when i have a better
understanding of them I'll build a monster. Thanks again
On Dec 14, 2013 2:20 PM, "Jim Lux" <jimlux@xxxxxxxxxxxxx> wrote:


On 12/14/13 4:55 AM, shane bounds wrote:


Hi, I'm building my first Tesla coil and was wondering if there is a
certain frequency you should try to reach with respect to the power of
your
transformer?



Not really.

The frequency of the coil is fairly unimportant as long as it's not too
high or low (for a small coil, 200-400 kHz is typical).  It's more
determined by the physical dimensions of the secondary winding.

What you want to do is size the coil to the size of the power supply: too
big a coil driven by a small transformer is tough to get to work.

A couple rules of thumb to get you started:
(and run a tesla coil simulation/design program like JavaTC)

the longest sparks you're likely to get is 1.7*sqrt(power in watts) (in
inches).  As a practical matter, a 12kV 30mA transformer is 360 W  will
give you sparks about 2 feet long.



You want the overall diameter of the toroidal electrode (top load) to be
at least 1/2 the height of the secondary coil, and more like equal. (at
least for small coils).  So if your secondary is 2 feet long, a toroid 2
feet in diameter would work.  1 foot will also work, but will be a bit
small.

The height of the secondary winding (not necessarily the tube it's wound
on) should be 4-5 times the diameter of the winding.  This is shorter and
more squat than a lot of pictures you'll see.  A 4 inch diameter coil would
then have windings that are 18 inches long, on a form that's a few inches
longer (to give you some room to mount it.


Figure on winding about 600-800 turns of wire on the secondary.



I found one formula, but I'm not sure about it,kHz= 3032.5xw^


-2767 - 96.4, not sure what the ^ is or if the formulas accurate. I've got
a 12kv 30 mA nst giving me 360 watts. I'm building it on paper first and
trying to get a good understanding of it and at the moment my secondary
will have a frequency of 322.6 kHz
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