# ceramic caps for tesla coil?

#### DerStrom8

##### Super Moderator
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
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

#### duffy

##### New Member
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:

#### DerStrom8

##### Super Moderator
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
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

#### lokeycmos

##### New Member
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 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. #### duffy ##### New Member Yes, doorknob caps will work, that's what's usually used. #### DerStrom8 ##### Super Moderator Most Helpful Member 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

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:

#### gary350

##### Well-Known Member
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:

#### gary350

##### Well-Known Member
I just sold 30 ceramic caps on ebay because they don't work well on tesla coils. Very high loss TC output sucks.

#### gary350

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

Last edited:

#### DerStrom8

##### Super Moderator

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!