[Prev][Next][Index][Thread]
RE: MMC to be?
>Original Poster: Adam <psycho-at-tradewind-dot-net>
>
>Ok, I'm thinking of building an MMC cap, but I'd like it if I could get
>some feedback on my plans from those who have built them before I start.
>
>My NST is 9kV at 30mA, so my target capacitance is going to be around
>.009uF
>
>What I'm wondering is whether I can use snubber capacitors. The ones
>I'm looking at are 3000VDC at .047uF. This means I should only need 5
>in series in order to get .0094, which is pretty close. The string
>would therefore be able to take 15000VDC, which is nearly 18% above the
>peak voltage of the transformer. I'm certainly overworking them, but
>given that others have had success driving MMCs at peak AC=DC, I think
>I'll be okay.
>
>This means my TC cap will cost me about $20.00 total, and will be
>extremely convenient.
>
>Unfortunately, all of this seems a little too good to be true.
>Please feel free to ruin my dreams before they mature! Comments would
>be greatly appreciated!
>
>Adam
Snubber caps do seem to be rated for high pulse current applications, and
with polypropylene dielectric, would be a good choice for a Tesla MMC.
While the voltage rating of the proposed cap sems OK, I'd be concerned
with using only one string, rather than several in parallel. With only
one string, the entire tank circuit current will be passing through each
cap, instead of being divided between several parallel paths. While the
Wima data sheets on my web site will tell you how much current a cap can
take, it's not clear what we coilers can actually get away with. I'm
sure I'm violating the peak current rating as well.
Regards, Gary Lau
Waltham, MA USA