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The mindkiller
Date: Thu, 1 Feb 1996 14:21:48 +0000
Subject: The mindkiller
>>>> Primary capacitor(s)
>>>> These are across the HV output and consist of 2 caps in series to
>>>> attain working voltage.
>>>> c1 0.0015uF 12Kv (large ceramic cap, big lugs)
>>>> c2 0.004 uF 20Kv Sangamo mica cap type g4R
>>>> ( I know these are not ideal i.e. low loss but they're all I've
>>>> got)
>>>> So that makes my cap about 0.0015 x 0.004 = 0.00109 uF
---------------
0.0015 + 0.004
>>>> is that a bit small? I could add the following caps in parallel,
>>>> do I need voltage balancing resistors if I do?
>>>> Best regards to all coilers
>>>> Steve Crawshaw
MG> Steve, first I think your capacitor value is too low, if the
transformer rating is about 50 ma I would suggest using around .005 ufd.
Second, you have a potential problem with connecting these caps in series,
assuming the transformer will develop 25 KV (it most likely won't) you stand
a VERY GOOD chance of destroying the .0015 ufd cap, and most likely both of
them. The reason is this, with these caps in series you'll have a reactance
at 60 hz of about 2,449,779 ohms, 1,769,285 in the .0015 ufd cap and
680,494 ohms in the .004 ufd cap. At 25 KV the total current flow through
these caps (60 hz.) will be about 10 Ma. being they are in series the
current is the same through both caps, but the voltage drops will not evenly
divide. The .004 ufd cap will have about 6,945 volts acrossed it and the
.0015 ufd cap will have about 18,055 volts acrossed it. Equalizing resistors
won't help here as you would have to use too many resistors to keep the
voltage acrossed each one low, and they would mostly likely affect the Q of
the primary circuit, in short they are not practical. I think I would use
the .004 ufd cap by itself and keep the gaps narrow and the transformer
backed down! I'm assuming these are D.C. voltage ratings and that just makes
it all the more vulnerable to failing.
Mark Graalman 71612,1234-at-compuserve-dot-com