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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
I had 6 inch sparks with a 6kv 30ma nst and now i have a new 12kv 60ma nst and the sparks ar no more than 4 inches. The nst is providing what it should be but i don't have any good capacitors. I don't even know what capacitance i am at now. I have a transparency capacitor, a mylar capacitor and a very small mylar capacitor. No matter what i can not get good performance with it. I am tired of this. I believe it is because either my caps are extremely lossy or i don't have the right capacitance. I don't have the money for good capacitors so i need to know why this is happening. I keep adding a party cup capacitor or two and it decreases the noise of the rsg, suggesting that it is too much capacitance. Well i am off to get get another piece of mylar to make another capacitor :'(.
Registered Member #1107
Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792
I would ditch the whole idea of making party cup caps because they are very lossey and unrealiable. Get some beer bottles and make beer bottle caps because they are much more reliable and the average capacitence is 1.5pf per cap. Also try to play with primary coil a little.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
teslacoolguy wrote ...
I would ditch the whole idea of making party cup caps because they are very lossey and unrealiable. Get some beer bottles and make beer bottle caps because they are much more reliable and the average capacitence is 1.5pf per cap. Also try to play with primary coil a little.
Well glass is lossy too. Well someone down the street from me has a few big plates of glass so i would rather get that. Sorry mike but i tried the party cup caps on the flyback and they are constantly sucking power out of it, meaning it will get hot(cause it did) and will suck more power than necessary(which it did). Plus i have seen some good glass plate caps, even though the are heavy and stuff, but they are so thick that i doubt they will ruin for a LONGG time.
Registered Member #477
Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546
marko666 wrote ...
Hi,I have a 12Kv 60ma NST too.I use 3 maxwell pulse caps adding up to 90 nF.They are in paralell. From this I get about 24 inches of arc.
Wow, why so much capacitance? That's about 6x as much as you probably should have. I don't doubt that it's seriously hurting your performance by keeping your firing voltage low. "More is better" cannot be universally applied in Tesla coil design! With a 12/60 NST, you ought to be able to get 40+" streamers without much difficulty. Having wayyyyy too much cap in a small coil is also going to force your hand on the primary design to the point where you'll probably have far too few primary turns, which adds up to very high primary currents and increased losses in the spark gap.
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
If you had 5 paralleled 12kV 60mA NST units then sure - I might just go with 90 nF worth of capacitance. I'm using 3 paralleled 12kV 60mA NSTs and I'm breaking 62.5 nF now... If your cap is too big then the caps won't charge in time and you'll get too low a voltage in gap. If the cap is too low in value then you'll blow the trannies up! Your coil has to be in balanced and phased correctly!
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
my calculations are 1.5x resonant. If you're interested in where I get that factor ( root(2) to 1.5) its on the fourm as ~ LTR calculations. That will give you maximum output. you should get ~32" from a 720VA transformer.
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Help with tesla coil.
That's about 6x as much as you probably should have. I don't doubt that it's seriously hurting your performance by keeping your firing voltage low. "More is better" cannot be universally applied in Tesla coil design! With a 12/60 NST, you ought to be able to get 40+" streamers without much difficulty. Having wayyyyy too much cap in a small coil is also going to force your hand on the primary design to the point where you'll probably have far too few primary turns, which adds up to very high primary currents and increased losses in the spark gap.