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

[CONOR WHYTE <cjwhyte@xxxxxxx>]

I don't use resistors on my MMC. I find these waste energy and cut down on my spark length. I  use CDE 942C series 1.6Kvdc 680nF capacitors, I use 20 per string 34nF @ 32Kvdc x2 . I run 12Kvac @ 240mA. I have been running my MMC now for 2 years and have had 0 problems. 
Quite often many people are scared about residual charge in the cap bank this is why people add the resistors. It bleeds charge away after the unit is turned off. You can do this with a discharge wand MUCH cheaper.
Like I said I have never used them. It is a waste of energy. 
If you feel like you want to protect your cap bank, I'd might make an extra gap that one could adjust.
maybe say to be safe a 3.5cm gap 35Kv.  I would also make sure the MMC total DC rating is around 3x that of the input voltage.  12Kvac -- 32-36Kvdc.  Another factor I would also check is the tolerance rating of the capacitors most are 5%... which is ok... CDEs on the other hand are 10% and can handle much more voltage spikes.
 

----- Original Message -----
From: vatercox@xxxxxxx
Date: Monday, August 18, 2008 10:47 am
Subject: [TCML] mmc cap protection by spark-gaps-any ideas?
To: tesla@xxxxxxxxxx

> 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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