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Registered Member #242
Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210
I found these caps at Electronics Goldmine. Will they work? the link Also, for my series strings, how much further should I go over the rated voltage? My NST is running at 15kV (30mA) and 9 in series will give me 16.2kV, is that high enough?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
No way. Use at least 30kV mmc or higher with equalizer resistors, 5-10nF is most often used for 30mA nst. And did you mean to put a link, add file or what..?
Registered Member #99
Joined: Thu Feb 09 2006, 06:10PM
Location: florida, usa
Posts: 637
Jrz126 wrote ...
I found these caps at Electronics Goldmine. Will they work? Also, for my series strings, how much further should I go over the rated voltage? My NST is running at 15kV (30mA) and 9 in series will give me 16.2kV, is that high enough?
Thanks, Jeff
As far as capacitor type, i havent seen any suitable for an MMC from electronic goldmine.
Registered Member #242
Joined: Thu Feb 23 2006, 11:37PM
Location: Erie PA
Posts: 210
ok, link is fixed...so those caps are out?...Where might I find some suitable caps? Would these work? 15kv 30kv The guy said he's sold them to other people before for TC use.
Registered Member #229
Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506
For safety, the voltage per string has to be: 15 kV * sqrt(2) * 2 = 42.3 kV. You can take a safety value = 2* 15 kV if dont have enough caps. 5600 pF are too small. For a 30 kV string you will have approx 17 cap per string, that means only 329 pF. You need a lot of caps to have enough primary capacitance.
The 15 kV and 30 kV caps seems to be used in the multipliers. I dont trust them in tesla coil service.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
the kind capasitors that might work are mika, doornob, mylar type, or pulse type capasitors. Stay away from dc filter capasitors. An easy way to make a capasitors is to take beer bottles cover the out side with aluiminuim foil and put salt water on the inside with a stainless 1/8" to 1/4" rod suspended by a wine corck or rubber stopper. Ebay is a good place to look, or your loacal electronics surplus store for comeersial capasitors.
Registered Member #135
Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735
Okay, let me first say something about Mica Capacitors. They were Not designed for Tesla applications. They do not handle the pulse well at all.
What you're looking at are 2 very different capacitors. On the left is a Sprague vintage 4000pF 30KVDC doorknob, and on the right is a modern Ceramic Laser pulse capacitor.
I have used the Mica 'In-test' with my Allanson 12KVAC 30mA transformer and they stored and discharged what appeared to be okay. But!! when you use them to the extent you may envision, like my 720VA TC, THEY SHORT! One of my 12 spragues I know is shorted! Not only that, but these capacitors were designed SOLELY for decoupling NOT pulse. The itty-bitty hardware studs are very evident of this! These caps are also notorious for changing value because they are not constructed of a uniform dielectric. This is bad, very bad. The stresses you place on a nonuniform dielectric cause it sresses which will later cause a short or failure.
On the other hand, the 2000pF uniform ceramic doorknob capacitors are designed for stress, pulse, quick discharge, and have very heavy terminals. They are being used in my system with great performance. The only drawback is that you must have two plates supporting them that can carry the current. I have had no problems with using circuitboard as the plates other then 2 very important issues. 1. The plate have No corners. No corners prevents charge from intensifying at the points. This prevents massive breakouts. I had to redesign my plates when this became clear. 2. Margins and arcovers must be prevented. My margin on both plates is 1.5" and one plate is corona doped. This has eliminated all arcover issues.
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Will these MMC caps work?
