Nathan and I looking
seriously cool in front of the 6-in coil. Nathan Helped a lot
with construction, I am on the right.
Primary:
1/4 in copper tubing, shallow cone.
Secondary: 1162 turns red 22 AWG magnet wire, 6-in PVC form.
Spark Gap: 120 BPS sync rotary
Tank Capacitor: 81 nf Maxwell pulse capacitor
Transformer: 8 kV Mot stack (225 ma)
Top Load: 7*24+12*30 stacked toroids (not shown in picture)
Input Voltage Control: 15A Powerstat Variac
Ballast: Single MOT.
Power Factor Correction Capacitors: 250 uf motor run caps.
Filters: (2) 10A EMI low voltage filters
Max arc length: 61 inches (est.)
Secondary: 1162 turns red 22 AWG magnet wire, 6-in PVC form.
Spark Gap: 120 BPS sync rotary
Tank Capacitor: 81 nf Maxwell pulse capacitor
Transformer: 8 kV Mot stack (225 ma)
Top Load: 7*24+12*30 stacked toroids (not shown in picture)
Input Voltage Control: 15A Powerstat Variac
Ballast: Single MOT.
Power Factor Correction Capacitors: 250 uf motor run caps.
Filters: (2) 10A EMI low voltage filters
Max arc length: 61 inches (est.)
Primary:
For my second generation Tesla coil, I decided to go for broke and get everything as big as I could (within reason of course). For my primary, I use 1/4 in copper tubing (which is the same as before, everything else is different).
Secondary:
For my secondary I am using a 6in. diameter PVC pipe wound tightly with 22 AWG magnet wire, about 1192 turns or 31in. (A little over actually) the height to width ratio is 5/1, which is optimum for a small coil, but will due nicely for a medium sized one like this (large Tesla coils have huge 18+in. diameter secondaries). Below is the new secondary in two stages of development, early winding on a jig, and complete, waiting for installation. The secondary is disattachable; I made it this way so that I could more easily transport everything. the Rf connection is a piece of copper sheeting tied the the last urn of secondary, which is clamped onto a ground wire. The 6-in secondary sits in a 6-in PVC pipe cap, which is "L" bracketed down to a piece of wood.
Transformers:
My power supply consists of 4 microwave oven transformers, with their primaries on one side in parallel, and the opposite in anti-parallel. The MOTs have the secondaries in complete series with opposite orientation on either side, with a center tapped ground, this orientation is important as it keeps both outputs at 4000+/- volts in respect to the ground, instead of a ground and then a 8+ kV output, which would really badly overrate the insulation on the MOTs (4kV is twice the rated value, 8 kV is 4 times).
Current Control:
It is important to note, I cannot safely just plug this thing in the wall, it will flip breakers like a dolphin at sea world (or grandma making pancakes, whichever analogy you prefer). So, an inductive ballast is being used along with power factor correction capacitors. For my ballast, I use a quick and easy single MOT with shorted secondary, and my PFC caps are motor run capacitors.
For
optimum coupling my primary coil is
adjustable up and down (around a stationary secondary) which is an
option I never
could exercise with my last coil. This allows me to get
maximum inductance (for best performance) and just keep it under the
point where it begins having secondary breakdown (racing arcs etc, very bad.) I can also
adjust the height of my topload from the top winding of my secondary,
which also makes a substantial difference in performance.
Some other goodies I have this time are a variac, and EMI filters. The variac allows me to adjust the voltage put into my MOTs, allowing me to adjust the voltage put out of my MOTs. This allows me to start up the coil slowly, reducing stress on all of the parts (preventing surge currents when all the cores are magnetizing). I also have some EMI filters, which filter out a lot of the RF "noise" transmitted back the AC power line, into my breaker box, where I do not want it.
Pictures:
Here are some half decent pictures of my coil in operation, for reference the arcs in the pictures below are about 30-40 inchers. I can get 40-55 on a good day! These images are unaltered except for cropping and resizing for a faster page load. I do not know the exposure time as Nathan took the pictures and his camera was set to "auto". I also have an animated gif, and a movie at the bottom; they give you a better idea of what it looks like real time, but do not do the real thing justice in any sense!
For my second generation Tesla coil, I decided to go for broke and get everything as big as I could (within reason of course). For my primary, I use 1/4 in copper tubing (which is the same as before, everything else is different).
For my secondary I am using a 6in. diameter PVC pipe wound tightly with 22 AWG magnet wire, about 1192 turns or 31in. (A little over actually) the height to width ratio is 5/1, which is optimum for a small coil, but will due nicely for a medium sized one like this (large Tesla coils have huge 18+in. diameter secondaries). Below is the new secondary in two stages of development, early winding on a jig, and complete, waiting for installation. The secondary is disattachable; I made it this way so that I could more easily transport everything. the Rf connection is a piece of copper sheeting tied the the last urn of secondary, which is clamped onto a ground wire. The 6-in secondary sits in a 6-in PVC pipe cap, which is "L" bracketed down to a piece of wood.
My power supply consists of 4 microwave oven transformers, with their primaries on one side in parallel, and the opposite in anti-parallel. The MOTs have the secondaries in complete series with opposite orientation on either side, with a center tapped ground, this orientation is important as it keeps both outputs at 4000+/- volts in respect to the ground, instead of a ground and then a 8+ kV output, which would really badly overrate the insulation on the MOTs (4kV is twice the rated value, 8 kV is 4 times).
Tank
Cap:
My capacitor is a professional Maxwell Pulse Cap rated for 75nf and 40kV, which is nearly half the optimum larger than resonant value capacitor for my transformer array (I got a great deal on it from a fellow Tesla coil enthusiast, who sold it to me for $100, it's worth up to $800 elsewhere). Yes, there is a piece of grass in from of the images, that is because I run this coil in the yard.
My capacitor is a professional Maxwell Pulse Cap rated for 75nf and 40kV, which is nearly half the optimum larger than resonant value capacitor for my transformer array (I got a great deal on it from a fellow Tesla coil enthusiast, who sold it to me for $100, it's worth up to $800 elsewhere). Yes, there is a piece of grass in from of the images, that is because I run this coil in the yard.
Spark
Gap:
For my spark gap I am "currently" using an synchronous rotary spark gap, propeller style. The center thoriated tungsten electrode rotates between 4 brass bolt electrodes at 1800 RPM. Because my cap and power supply are not correctly matched, I should be using an asynchronous gap, but this one works nicely for now. I am running it at 120 bps.
Wiring:
I use 10 AWG wire for low current connections, but I used 2 parallel strands of 6 AWG wire for the tank circuit (where peak current is over 600 AMPs). The formula for arc length in inches is 1.78*sqrt(transformer wattage) and for my power level I should get around 8ft arcs (assuming 1000 watts per transformer, with losses, this gives an 8 ft output as an estimate! In reality it is limited to a much lower power level, so 54 inches of spark isn't all that bad.)
For my spark gap I am "currently" using an synchronous rotary spark gap, propeller style. The center thoriated tungsten electrode rotates between 4 brass bolt electrodes at 1800 RPM. Because my cap and power supply are not correctly matched, I should be using an asynchronous gap, but this one works nicely for now. I am running it at 120 bps.
I use 10 AWG wire for low current connections, but I used 2 parallel strands of 6 AWG wire for the tank circuit (where peak current is over 600 AMPs). The formula for arc length in inches is 1.78*sqrt(transformer wattage) and for my power level I should get around 8ft arcs (assuming 1000 watts per transformer, with losses, this gives an 8 ft output as an estimate! In reality it is limited to a much lower power level, so 54 inches of spark isn't all that bad.)
Current Control:
It is important to note, I cannot safely just plug this thing in the wall, it will flip breakers like a dolphin at sea world (or grandma making pancakes, whichever analogy you prefer). So, an inductive ballast is being used along with power factor correction capacitors. For my ballast, I use a quick and easy single MOT with shorted secondary, and my PFC caps are motor run capacitors.
Other
Goodies:
Some other goodies I have this time are a variac, and EMI filters. The variac allows me to adjust the voltage put into my MOTs, allowing me to adjust the voltage put out of my MOTs. This allows me to start up the coil slowly, reducing stress on all of the parts (preventing surge currents when all the cores are magnetizing). I also have some EMI filters, which filter out a lot of the RF "noise" transmitted back the AC power line, into my breaker box, where I do not want it.
Pictures:
Here are some half decent pictures of my coil in operation, for reference the arcs in the pictures below are about 30-40 inchers. I can get 40-55 on a good day! These images are unaltered except for cropping and resizing for a faster page load. I do not know the exposure time as Nathan took the pictures and his camera was set to "auto". I also have an animated gif, and a movie at the bottom; they give you a better idea of what it looks like real time, but do not do the real thing justice in any sense!
