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Registered Member #1745
Joined: Wed Oct 08 2008, 12:29AM
Location: Northen Michigan, US
Posts: 19
Im building a static spark gap tesla coil, and Im waiting on parts to come in, but have a general idea on how things will be put together. So, heres my setup:
12kV NST, 60 Hz, 30mA RFI Filter Cornell Dubillier 942 CDE .15 uF capacitor rated at 2000V (ill be making a string of 22 to get a capacitance of .00682 uF) tungsten spark gap w/copper connectors 1/4" copper tubing (for primary, plan to do about 14 turns spaced at 1/4 inch) 22" secondary wound with 26# wire (approximately 1100 turns) 3x12" toroid
Heres a poorly drawn mod edit: and oversized and generally noobish schematic:
Please, correct me if Im wrong on anything, or give me some suggestions on how I could improve the setup. Thanks guys!!!
Registered Member #1535
Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117
That's almost a perfect match to my first coil. I also added Terry's NST filter. It worked good. I upgraded to a propeller style rotary gap and it worked even better.
I made a vertical helix for my primary. I think I would have been better off with a flat pancake. Yours?
Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
Everything is looking pretty good. One suggestion i would like to make is to replace the safety gap with a terry filter . It will extend the life of your nst more then a safety gap.
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
I think your capacitor is too small. LTR for your NST is about 10nF, you could use a string of 15 to achieve this and still have a voltage rating of 30kV.
Registered Member #1745
Joined: Wed Oct 08 2008, 12:29AM
Location: Northen Michigan, US
Posts: 19
TheBoozer wrote ...
That's almost a perfect match to my first coil. I also added Terry's NST filter. It worked good. I upgraded to a propeller style rotary gap and it worked even better.
I made a vertical helix for my primary. I think I would have been better off with a flat pancake. Yours?
You didn't mention secondary O.D.
Yeah, I plan on doing a flat primary lol. And my outer diamter is about 4.2" on my secondary
teslacoolguy wrote ...
Everything is looking pretty good. One suggestion i would like to make is to replace the safety gap with a terry filter . It will extend the life of your nst more then a safety gap.
I was debating on whether or not to add a terry filter, so I think I will
Coronafix wrote ...
I think your capacitor is too small. LTR for your NST is about 10nF, you could use a string of 15 to achieve this and still have a voltage rating of 30kV.
Ive tried out some online calculators (deepfriedneon.com's for example) and they calculated it to be .0066 for my transformer, so I dont know :S
Registered Member #160
Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938
6.63nF is your resonant cap size (I'm assuming 60Hz line frequency) for a 12kV30mA NST. With a static spark gap it is recommended that you use a larger than resonant capacitor, usually 1.4-1.5 times resonant value. This gives a cap value of 9.3-9.9nF. At resonance your cap can see some extreme voltages and even though you have a bank design that could handle that, chances are your NST won't survive this. More info here
Registered Member #1745
Joined: Wed Oct 08 2008, 12:29AM
Location: Northen Michigan, US
Posts: 19
Coronafix wrote ...
6.63nF is your resonant cap size (I'm assuming 60Hz line frequency) for a 12kV30mA NST. With a static spark gap it is recommended that you use a larger than resonant capacitor, usually 1.4-1.5 times resonant value. This gives a cap value of 9.3-9.9nF. At resonance your cap can see some extreme voltages and even though you have a bank design that could handle that, chances are your NST won't survive this. More info here
Thanks, that information was very helpful. Im going to change my cap chain to about 16, giving me a capacitance of .00938 uF. If needed, I can remove one for a nice clean 0.01 uF. Theres always time for experimentation
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So how do you think this will work out?
