Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Hi Michael,
4" diameter would be good. We average a diameter to height ratio of
4 to 5. Thus, your coil length might be 36" to 40". With the 30awg
size you suggested, you can expect 1350 turns for the 4:1 h/d to
1700 turns for the 5:1 h/d. If you desire to build somewhere in the
neighborhood of 1000 turns, then 26 awg will yield 1100 turns for
the 5:1 h/d coil.
The 4kV, 30mA is a rather low voltage, but it has been done (about
15" sparks are possible). It appears your trying to build around a
particular cap size which I assume you have already built or
purchased (4800pF)? Ok, you can do that. But first, the .0199uF
which Javatc calls out down in the transformer outputs is the
resonant capacitor value at which a 60Hz resonant circuit will be
established for the transformer parameters you entered. This "does
not" indicate that you are required to use this value for the tank
cap. The value is there as a reference tool. (Usually, so that you
can stay away from this value). There are circuits where this value
would be beneficial, but that is beyond the scope of my reply here.
For info on resonant charging, see
http://www.richieburnett.co.uk/resonant.html#resonant.
Also, the primary using 1/4" copper tubing is perfect. Simply enter
the wire diameter. Solid wire or tube is not a factor with
non-magnetic inductors, only the geometry is required. Keep about a
0.75" to 1" space between the inner turn of the primary to the
secondary (this value measured at the inner start of the primary).
If you were to go for the 5:1 h/d above at 1100 turns, your looking
at a self-resonant frequency of 389 kHz meaning the coil has no
topload. The primary at 2.75" i.d. and 8.25" o.d. (1/4" tubing w/
1/4" spacing) will be right at 390 kHz with the 4800pF cap size. Of
course, you will add a top terminal for spark discharge. If the
terminal is very small (say a 3" sphere placed 5" above the coil),
the secondary resonant frequency will drop to 337 kHz. Seems
dramatic for a small sphere, but it is what it is. A large toroid or
similar object will drop the frequency even farther. The top volts
will be low with your transformer (about 130,000) and a large radius
of curvature will make breakout difficult. If you do use a toroid or
similar, you may need a breakout point of some type.
In any respect, the topload drops the frequency, so with a fixed cap
size, you will need to adjust the primary turns. For reference, when
you see the secondary frequency lower, you increase your primary
turns to lower the primary frequency to that of the secondary for
resonance. For the sphere dimensions above, this would work out to
12.6 turns. It's a good idea to run the coil with scrap wire (sloppy
is ok) to experimentally arrive at the actual turns you will need,
then later build the nice tube primary for the topload size you
decide on. If you plan to run different toploads, then build the
primary for at least the largest topload you will use.
The gap will likely be a static gap of some type. Due to the low
voltage transformer, the spacing will be pretty close and the
electrode diameter will be thin. For example, you will probably need
to stay in the range of a .125" diameter at a very narrow .08" total
gap. It will heat up fast and runs will be short (sparks drop fast
as the electrodes heat up and begin to conduct across the gap at
lower and lower voltages). A fan will be necessary to aid electrode cooling.
Any questions on Javatc's use, just contact me offlist.
Take care,
Bart
Tesla list wrote:
Original poster: "Michael Ong" <omenowner725@xxxxxxxxxxx>
thanks for your referals to go to those sims they work wonders.
also, i think i am going to go with a 4 in diameter instead like
you suggested the inductance is a lot higher. however, i do have a
few more questions that have been confusing me with these
simulators. the first is if the res cap size for a 4kv 30ma 60hz
transformer is .0199 uf why does the coil i am trying to build call
for a 4800pf cap? the next question i had was that i pan on using
1/4 inch copper water tubing for the primary. since this is hollow
is there a way for javatc to take into account that the wire
dismeter is not a solid 1/4" but instead a hollow tube with a
certian thickness?
thanks again for all your time and willingness to help beginning
tesla coilers like myself.
From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: calculations
Date: Fri, 11 Nov 2005 21:05:59 -0700
Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
Since your voltage is so low, I would definitely consider going to
a 4 inch dia coil as inductance goes up as square of the radius of
the coil and inductance x rate change of current (dI/dt) is what
produces voltage.
Dr. Resonance
hello, i am going to be building a tesla coil modled after one
on the internet that's a 4kv 4800pf primary 11 turns of 1/4 inch
coper secondary 1000 turns of 30 AWG with a pvc diameter of 2.5
inches. i was wondering how do you get these numbers. like how
do you know how wide the coil has to be. or the turn ratio, or
how do you find the frequency of the coil so you can determine
the value of the capacitor you need. any calculations that you
guys know to solve for these things would be very helpful. i
would like to get to the point where i can make a coil totaly on
my own. thanks agian for all the help
-michael