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ceramic caps for tesla coil?

DerStrom8

Super Moderator
Most Helpful Member
#2
What kind of ceramic caps? Do you have links? I have heard of them being used, but they are not usually all that efficient. You will need to read up on all the specs, just to be sure. I'm afraid I never got past the low-cost homemade caps, so I probably won't be able to help with the professional caps. I'm sure other members here can help a lot, though.

Regards
 

DerStrom8

Super Moderator
Most Helpful Member
#4
http://www.ebay.com/sch/i.html?_nkw...pg=50&LH_BIN=1&_sop=15&_osacat=4662&_from=R40

im using a 15kv transformer so peak is about 22kv. i can buy a few 30kv caps and put them in parallel to reach my goal of 8.6nF
The problem with most professional caps for Tesla coils is their efficiency. Most capacitors are very lossy at high frequencies, so it is difficult to find ones that will work properly. Again, I don't really have much experience with MMCs, but other members here might. I'm just as eager to get an answer as you are :D
 

duffy

New Member
#5
Use polyester or polypropylene. Try running it with ceramics for a few minutes, then turn it off and feel how hot they get. Then try the same thing with poly caps. HUGE difference.


Oh, wait - 22KV? Nevermind, dunno from 22kv caps.
 
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DerStrom8

Super Moderator
Most Helpful Member
#7
how about these? i can make an MMC. they are only rated for DC there is no AC rating for them? i can afford these.

http://www.ebay.com/itm/0022uF-15KV...686?pt=LH_DefaultDomain_0&hash=item3cb6abbb56

this is the data sheet for them:

http://www.ecicaps.com/capacitors/features/4me12-series-high-voltage-metallized-polyester-capacitors
If you're building an AC-powered tesla coil, these DC caps will not work. They are intended for DC and may explode if high voltage AC was applied to them. you could, however, switch your TC over to DC, but it would require a few extras (like high-voltage rectifiers).
 

duffy

New Member
#8
Metallized polyester caps aren't polarized, they aren't constructed like electrolytics. The dielectric's a layer of plastic film, not an oxide, and it works both ways. Note that there's no polarization, even in the spec sheet. Yes, it says "kVdc" on it, but that's just the dc rating.

Unfortunately, the AC voltage rating is always less than the dc voltage rating on poly caps, and usually by quite a bit. http://www.electro-tech-online.com/custompdfs/2011/11/ABD0000PE111.pdf
 
Thread starter #9
Metallized polyester caps aren't polarized, they aren't constructed like electrolytics. The dielectric's a layer of plastic film, not an oxide, and it works both ways. Note that there's no polarization, even in the spec sheet. Yes, it says "kVdc" on it, but that's just the dc rating.

Unfortunately, the AC voltage rating is always less than the dc voltage rating on poly caps, and usually by quite a bit. http://www.electro-tech-online.com/custompdfs/2011/11/ABD0000PE111-1.pdf
so, your pretty sure with a good deal of certainty that they will work? i can order 16 for bout 40$ to make a MMC with a DC rating of 30kvdc 8.8nF. im using 15kv transformer so peak AC is about 22kv
 

duffy

New Member
#11
so, your pretty sure with a good deal of certainty that they will work?
No, I'm just sure they aren't polarized. I've seen poly cap AC ratings that were one-TENTH the DC rating. Without telling you that number, I'm afraid those things are still a crapshoot.
 

DerStrom8

Super Moderator
Most Helpful Member
#14
If you can afford doorknob capacitors, then yes, they'll work great. They are very popular in Tesla coil applications, as they have excellent insulation and a low ESR. They are also not likely to lose energy, even at very high frequencies. I simply was never able to afford them, as they often cost $20-$100 a piece :p

EDIT: Just looked at the link. You'll need 4 of them in parallel, so that means you'll have to buy two sets as shown there on ebay.
 
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gary350

Well-Known Member
#15
An empty beer bottle full of salt water wrapped with aluminum foil on the outside makes a better TC cap than ceramic caps and these are not real efficent.
 
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gary350

Well-Known Member
#18
WHY did I receive a message in email that someone replied to this thread? Nothing new here this was 12 years ago.
 
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DerStrom8

Super Moderator
Most Helpful Member
#19
Are you sure it was this thread? There was another similar thread that came up recently....

I just checked, there were no spammer posts or anything that would have triggered a notification. Also, how'd you end up in 2024? I'm still back here in 2017!
 

gary350

Well-Known Member
#20
Are you sure it was this thread? There was another similar thread that came up recently....

I just checked, there were no spammer posts or anything that would have triggered a notification. Also, how'd you end up in 2024? I'm still back here in 2017!

It came up in my email just like this one did. I clicked the link and here I am on the forum.
 

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