Re: A few questions about coil designing

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 




By using a large toroid you can overcome this effect by loading the sec down
heavily.  This also allows much larger pri cap and more power input so the
resulting output is very spectacular.

A great formula for large coils:  large toroid, lots of sec turns
(1,200-1,400), large pri cap, and lots of drive power.

The large toroids are inexpensively made with plywood, styrofoam, and
chicken wire mesh.  I think Terry has archived some photos I submitted on
this type of construction.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
-dot-com>
 >
 > David: Just a quick responce. Your secondary is only 897 turns not 1500
 > turns so it will resonate at a high frequency. Your capacitor is o.1 ufd
 > over twice the value neaded for 1500 turns so your primary will be way to
 > low. Even if you use both your capacitors in series you may still have
more
 > capacitance than neaded for your low turn secondary.
 >       Robert   H
 > --
 >
 >
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > Date: Thu, 18 Nov 2004 21:02:14 -0700
 >  > To: tesla-at-pupman-dot-com
 >  > Subject: A few questions about  coil designing
 >  > Resent-From: tesla-at-pupman-dot-com
 >  > Resent-Date: Thu, 18 Nov 2004 21:04:24 -0700
 >  >
 >  > Original poster: "David Rieben" <drieben-at-midsouth.rr-dot-com>
 >  >
 >  > Hi All,
 >  >
 >  > I am in the process of constructing a fairly big coil with a 12 3/4" x
 >  > 44" long secondary wound with 897 turns of #17 heavy build Essex
 >  > magnet wire. That makes for just over 3000 feet of wire.
 >  > The primary is 12 spiralled turns of 5/8" OD soft copper
 >  > tubing with the outer most turn at nearly 40" diameter. There is an
 >  > approximate 1/2" spacing between each primary turn.
 >  >
 >  > For the primary capacitor I will be using either one or two paralleled
 >  > .1 uFd, 50 kV Hipotronics commercial pulse capacitor(s). These are
 >  > Tesla coil specific custom capacitors that Jeff Parisse was using for
his
 >  > Model 10 coil. I'm thinking that .1 uFd will be sufficient primary
 >  > capacitance for my design.?
 >  >
 >  > The power supply will be either a 10 or 15 kVA, 14,400 volt pole trans-
 >  > former (have one of each), controlled and ballasted with (2) paralleled
 > 1256D
 >  > Powerstats and a Lincoln 225 amp arc welder core set for the maximum
welding
 >  > amperage. The arc welder's core guts have removed from the factory
steel
 >  > box and placed in a tank of transformer oil to increase the duty cycle.
 >  >
 >  > The rotary gap will most likely be ASYNCH G-10 and tungsten
 >  > with a variable speed DC or universal drive motor. I may have to
 >  > break down and pay someone to do this part for me as i am
 >  > no machinist and I do want it to be right :^))))
 >  > I have designed and built big coils before but I want to make sure
 >  > that I get this one right the FIRST time ;^)
 >  >
 >  > My questions are: Will there be a problem of turn/turn flashover
 >  > on the outer turns of the primary coil since there is often less than
 >  > 1/2" spacing between the adjacent turns? If it's tapped at say the 7th
 >  > turn then there's 5 additional unused turns that can develop an auto-
 >  > transformer effect. I may just remove most of the unused turns if
 >  > this proves to be a problem once tuned in.
 >  >
 >  > Also, my Hipotronics pulse caps are the single bushing, steel
 >  > can type with the steel case grounded to the terminal opposite
 >  > of the bushing. I'm thinking that I'll need to place the capacitor
 >  > in parallel with the transformer instead of the spark gap in paral-
 >  > lel with the same, otherwise I'll end up with the entire exterior
 >  > case of the capactior floating at 14,400 volts ;^O. I've heard that
 >  > this wiring variation of the primary circuit places more strain on
 >  > the transformer but since I'm using a pole transformer, I don't feel
 >  > that this will be an issue in this case.
 >  >
 >  > I plan on building a 12" minor diameter toroid from aluminum flex-
 >  > duct tubing from McMaster-Carr, with a major diameter of 48" to
 >  > 54". I'll probably also use a smaller toroid (4" minor diameter x
 >  > 16 to 20" major diameter) for a corona shield of the topmost
 >  > turns of the secondary. With a toroid this large, will .1 uFd be
 >  > sufficiently large for the primary capacitor? It seems that my
 >  > power supply combo may not have suffiecient power to drive
 >  > .2 uFd of primary capacitance. Any comments welcome ;^)
 >  >
 >  > David Rieben
 >  >
 >  >
 >
 >
 >