mmc capacitor banks

[OakleyC]

Hi all

I have been building a dual MOT 110mm tesla coil. I want to make/buy my capacitors now. My question is, am I better off making my own flat capacitor (as rimstarorg made his but with like 150nf capacitance) or buying something similar these Capacitors.

Will these work? They seem a lot cheaper than the cornell-dubilier capacitors. I am aiming for around 150nf at 10kv.

Thanks for your time.

OakleyC


*edit
They also have these ones here.
I calculated I will need 30 to make a 204nf 10kv bank which I think is cheaper than buying lots of smaller caps.

[Hydron]

I believe that others have asked about the same capacitors on the forum, I don't remember the exact conclusion (I believe they have actually been tested) but I personally was and still am rather dubious of something without proper specs or datasheet. They don't even state the dielectric material!

[OakleyC]

Hmm good point on not having a datasheet! What about making my own flat capacitor with pp sheets and aluminium foil? I have seen tesla coils with 50nf in beer bottle capacitors working well but I don't want to work with liquid and high voltage I would rather have it dry (or maybe oil soaked if i have too but I am only running it at 4.2kv). I had a bit of a look around and found loneoceans post on capacitors. I have a very tight budget though and would rather only spend $50 on caps. All of those caps are like $3+ each which is too much when i'm going to buy like 100 of them. Is it ok to link 4hv and other forums to here?

[profdc9]

I actually used the capacitors at hvstuff and they worked.  I have used these capacitors
 
http://hvstuff.com/0-04uf-10kv-high-voltage-capacitor-hv-tesla-coil-ham
http://hvstuff.com/0-1uf-10kv-high-voltage-capacitor-hv-tesla-coil-ham

Also might be useful

http://hvstuff.com/0-02uf-15kv-high-voltage-capacitor-hv-tesla-coil-ham
http://hvstuff.com/0-01uf-20kv-high-voltage-capacitor-hv-tesla-coil-ham
http://hvstuff.com/2kv-0-15uf-high-voltage-capacitor-hv-tesla-coil-ham


You may not want to get one big capacitor.  The peak current ratings tend to be 250 A or so, so its better to use several smaller capacitors in parallel.

Dan

[Mads Barnkob]

Hi Oakley

Those are the "good and old" "Panasonic" capacitors, the reason I write both in situation marks is that they were the best back then, as pulse film capacitors was out of the reach for the amateur and it used to be Panasonic that made them, that is hardly the case anymore

I once found the specs and added the panasonics to my MMC calculator, so take a look there: http://kaizerpowerelectronics.dk/calculators/mmc-calculator/

Look at the Panasonic ECWH16333, Panasonic ECWH16473 and Panasonic ECWH16563: http://kaizerpowerelectronics.dk/theory/good-mmc-capacitors/

[OakleyC]

Ok thank you all for all the information! I think I will try making my own polyethylene and aluminium foil capacitor. If the results of that are poor I will buy the cheap china capacitors. If they are all bad i will save up for a cornell dublier capacitor bank.

  Oakley

[Mads Barnkob]

Ok thank you all for all the information! I think I will try making my own polyethylene and aluminium foil capacitor. If the results of that are poor I will buy the cheap china capacitors. If they are all bad i will save up for a cornell dublier capacitor bank.

  Oakley

Good luck with building your own You are going to learn a lot about creeping distances, field shaping and the importance of removing air in order to avoid corona discharges/losses/damages. Building your own can be cheap but not very effective. I would advise you on trying to roll it instead of making a stack of flat sheets. Roll it insanely tight around a larger diameter pipe to get good compression from the middle and out.

Inbetween getting CDE 942C and cheap chinese capacitors is the surplus market of large quantities of brand name leftovers from the industry, check out a good seller like this: http://www.ebaystores.co.uk/zhoefler/Elektronikbauteile-allgemein-/_i.html?rt=nc&_nkw=capacitor&_fsub=2&_sacat=zhoefler&_sid=26870231&_trksid=p4634.c0.m14.l1581&_pgn=3

There is a wide range of cheap 20-100 pieces in a lot MKP capacitors of various capacitance and voltage rating, some of them are vital for a MMC, depending on how much you are willing to solder together