RE: [TCML] mmc cap protection by spark-gaps-any ideas?

["S&JY" <youngs@xxxxxxxxx>]

No, no, no!  Don't do that!  If one or more of the gaps fires, the other
caps in series will overvolt which could cause them to fail.  

The resistors are not to protect the caps.  They are to protect you from an
accidental dangerous shock by bleeding down the voltage stored in each cap
in a few seconds after you turn off power.  

You can make good high voltage resistors by series connecting 5 2 meg 1/4
watt resistors.  Connect one of these resistor strings across each cap.
Yes, lots of soldering, but the resistors are only 1 US cent apiece (get
them in lots of 100 from Jameco).

--Steve Y.

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of vatercox@xxxxxxx
Sent: Sunday, August 17, 2008 3:23 PM
To: tesla@xxxxxxxxxx
Subject: [TCML] mmc cap protection by spark-gaps-any ideas?

Dear List
I have 30 x 47nF polypropylene metal foil caps, each rated at 2 kVDC 
which I intend to wire as three strings of 10 capacitors for 
approximately 14nF at 20kV DC. While normally each capacitor in an MMC 
would be protected by a 10- or more megohm high voltage resistor these 
have proved difficult to obtain (due to lack of demand?). In liu of 
this would it be possible to protect each cap with a miniature 
spark-gap -perhaps a pair of closely-positioned stiff wires connected 
to the capacitor leads notwithstanding the fact that 2 kV is usually 
regarded as a bit on the low side for satisfactory spark-gap operation

Jolyon Francis Vater-Cox
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