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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
This s quite an old topic, but i would like to bring it up again.
Has anyone used this in tesla coil duty? I am going to head to office depot and pick some up, because everything i have tried failed miserably, either by arc-overs or not enough capacitance even though it is very large. The only caps i could afford are pieces of (Ill let you fill in the blank).
I am going to use 2 sheet and make a few of those because i need a 20nf capacitor and a 40nf capacitor. The capacitors will be used at 6kv for the 20nf and 16kv for the 40nf. Do you think 2 sheets will be sufficient for short runs at 16kv max?
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
I used these caps for my MOT + voltage quadrupler driven SG coil and I had no failure (and it was single sheet design - it means three sheets per cap in total). But it was only short time tested - I had to give up with this coil because it was too noisy for a "block of flats" use. Since you are going to use two sheets design (it means 4sheets per cap in total) you don't need to glue the sides of the caps and for 16KV two sheets should be far enough (each sheet can stand 14KV). And there is no point of using oil unless you own vacuum pump. It’s messy and makes the cap even more vulnerable (ozon + oil = nasty acids eating the PP-CP). Good luck and let us know how it works…
BTW: in Hv-Wiki in how to section is a bit better version of the protocol...
One more thing: I find out that its better to use more caps in series rather then adding more sheets in case you want higher voltage raitng. You will never need to perform the side-gluing part of the protocol. So ideal design is two sheetsbased caps (4sheets in total = 25KV rated) used it in a MMC setup like I used in this project , however it has higher space demands...
and what about design with no rolling, just more plates??? i think it will be easier to build, less space needed, and you can add it in plexiglass so the plexi will do a pressure on it...
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
dingo27 wrote ...
and what about design with no rolling, just more plates??? i think it will be easier to build, less space needed, and you can add it in plexiglass so the plexi will do a pressure on it...
1) Rolled cap has bigger capacitance
2) Unrolled cap will be flat but otherwise the full A4 size !
3) Plexiglass is another extra material, which means extra costs and extra processing work
In general the flat design is doable but seems unpractical to me... but feel free to try your own design and let us know
Registered Member #10
Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424
I have plans for a Tesla suitable rolled cap which might just be good enough to be used without oil and be easy to make. Hopefully a significant improvement on the old rolled caps which were prone to failure even with oil. There have been a few insights into rolled cap making now that I have experience and a better understanding of the spiral line impulse generator. I really need to make it up and do the testing first though and I have a few other things on the go at present. I should also do a detailed contruction sequence like the comprehensive one Mates has done.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Tesladownunder wrote ...
I have plans for a Tesla suitable rolled cap which might just be good enough to be used without oil and be easy to make. Hopefully a significant improvement on the old rolled caps which were prone to failure even with oil. There have been a few insights into rolled cap making now that I have experience and a better understanding of the spiral line impulse generator. I really need to make it up and do the testing first though and I have a few other things on the go at present. I should also do a detailed contruction sequence like the comprehensive one Mates has done.
TDU
Well whenever you get those caps made, give us the instructions, I am sure alot of us would use it and really appreciate it. Now all i have to do is make a transformer (not) and every part on my tesla coil is home made .
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Ok, so my birthday was yesterday and i got some transparencies. They work good and have quite high capacitance. But no matter how many i use, i still get much poorer performance that the cje caps i used. Maybe i just haven't found the ideal capacitance? Or is it because of inductance and other stuff i know nothing about?
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Arcstarter wrote ...
Ok, so my birthday was yesterday and i got some transparencies. They work good and have quite high capacitance. But no matter how many i use, i still get much poorer performance that the cje caps i used. Maybe i just haven't found the ideal capacitance? Or is it because of inductance and other stuff i know nothing about?
I do not understand your point. The capacitance is defined by the size of the alu foil (how bigger so bigger) and by the distance between these foils (how smaller so bigger). Special factor is the rolling... So if you use only one sheet of transparency isolating the two alu foils (three transparencies in total) than you should see like 12-13nf and the cap should stand 14KV... I do not know what is it cje but i think that is quite a powerful and cheap cap.
BTW: I tested these caps with my flyback based SGTC recently and they work fine... No problems after really long run - the caps get only litle bit warm (corrona losses) but the dielectricum looks uneaten...
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Oops. I forgot what i was saying while i was typing. Don't ask. I meant on my tesla coil. I used them on my tesla coil and i got less performance than with a capacitor bought on ebay. And now i have one of them arcing over. But i can see the corona which looks like the sparks off the tesla coil but alot more sparks but alot shorter.
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60KV 3.5 nF home made caps - complete protocol
