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Re: A few questions about coil designing



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


You will achieve greater performance if you can use a smaller guage wire to
hit 1,200 to 1,400 turns on your sec coil.

With 3,000 ft of wire on the sec coil, your 0.2 cap bank will perform
excellent if driven at 15 kVA to 20 kVA power level.

At this power level use G-10 1/2 inch thick rotor x 16 inch dia with
electrodes on 15 inch dia circle.  Use 1.25 inch long 1/2 inch dia brass
axial feedthrus to which are affixed your thread in type 1/2 dia. tungsten
tips.  Use 1 inch dia. tungsten tips for the 4 stationary electrodes.  At
this power level I recommend breaking with 2 gaps on each side of the rotor,
ie, 4 gaps all connected in series for good quenching.  Use a DC motor to
achieve RSG speed control.  Use 12 electrodes on the rotor wheel.

1/2 inch pri gap is tight but you can use a long "U" shaped from flat copper
strap to form a thin pri attach clip.  In your upper sub-base support cut 3
axial holes 1 inch wide x 3/4 length of pri coil width.  You can check
different locations to find the best tuning location with these 3 holes
available.

Use some scrap 10 AWG wire for initial tuning and add the copper tubing
later after you determine total number of turns necessary.  Use this
experimental determined value and add 2 more turns for the final copper
tubing winding.

You should place the sparkgap in parallel with the power feed.  If it's a
pole xmfr, just ground one bushing and run single ended thus allowing you to
keep your cap cases at ground potential.  We use this type of setup on all
of our large coils.

Dr. Resonance


 >
 > 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
 >
 >
 >