RE: Geek MMC vs Teflon film cap.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Snoswell by way of Terry Fritz <teslalist-at-qwest-dot-net>" <mark-at-cgCharacter-dot-com>

Thanks for that... I am still weighing up using the Teflon film I have
or making up a MMC.

425 feet of 0.001" Teflon x 6" wide cost me about A$250

I can make up about 0.010uF cap with breakdown rating of 204 KV AC --
de-rating to just 10% of breakdown gives a 20 KV AC working voltage.

Or if I drop the safety margin to 29% of breakdown then I can get about
0.09uf with a breakdown rating of about 70 KV AC.

With a MMC I should get 0.007 uF with 43 x 0.33uF caps in series which
gives a voltage rating of 20 KV AC  (45 KC DC) which will cost A$189  --
which is not too far off the cost of the equivalent Teflon cap --
although the Teflon should give a cap with 10x or so lower ESR at 100 -
200 KHz.

If I de-rate the Teflon cap then the equivalent MMC cap would cost
A$2,440 -- almost 10x more expensive than "home made" Teflon film cap.

Q: Just how much do people over-rate their MMC caps? ... For instance
the Cornell-Dubilier 942C16P33K 0-33MFD is rated at 1600VDC but only
465V AC... Do people stick to the AC ratings?

Thanks

Mark

  <tesla-at-paradise-dot-net.nz>
|You are fortunate to have a CDE agent in Adelaide. They are KD Fisher
Ltd.
|
|942C20P15K      0-15MFD  2000VDC     M.O.Q.  20   AUST$4-30ea
|
|942C16P33K      0-33MFD  1600VDC     M.O.Q.  20   AUST$4-40ea
|
|KEN  FISHER  (General Manager)
|Adelaide, South Australia,
|ph   08-8277 3288     ( Int.)-61-8-8277 3288
|email   kenf-at-kdfisher-dot-com.au

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