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ceramic caps for tesla coil?

Discussion in 'High Voltage' started by lokeycmos, Nov 16, 2011.

  1. lokeycmos

    lokeycmos New Member

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    will high voltage ceramic caps work good for a tesla coil? i initially make a bucket cap, but im finding some decent prices on 30kv ceramic caps on ebay.
     
  2. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    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
     
  3. lokeycmos

    lokeycmos New Member

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  4. dave

    Dave New Member

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  5. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    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
     
  6. duffy

    duffy New Member

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    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.
     
    Last edited: Nov 16, 2011
  7. lokeycmos

    lokeycmos New Member

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  8. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    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).
     
  9. duffy

    duffy New Member

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    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
     
  10. lokeycmos

    lokeycmos New Member

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    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
     
  11. jpanhalt

    jpanhalt Well-Known Member Most Helpful Member

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  12. duffy

    duffy New Member

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    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.
     
  13. lokeycmos

    lokeycmos New Member

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  14. duffy

    duffy New Member

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    Yes, doorknob caps will work, that's what's usually used.
     
  15. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    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.
     
    Last edited: Nov 19, 2011
  16. gary350

    gary350 Well-Known Member

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    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.
     
    Last edited: Dec 21, 2011
  17. gary350

    gary350 Well-Known Member

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  18. gary350

    gary350 Well-Known Member

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    I just sold 30 ceramic caps on ebay because they don't work well on tesla coils. Very high loss TC output sucks.
     
  19. gary350

    gary350 Well-Known Member

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    WHY did I receive a message in email that someone replied to this thread? Nothing new here this was 12 years ago.
     
    Last edited: Apr 16, 2017
  20. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    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!
     
  21. gary350

    gary350 Well-Known Member

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    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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