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

["David Nelson" <davidnelson11@xxxxxxxxxxx>]

How much energy is lost in the MMC resistors? Surely it is a small 
percentage?

It seem to me that most people highly recommend them for safety reasons.

Dave Nelson
----- Original Message ----- 
From: "CONOR WHYTE" <cjwhyte@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, August 18, 2008 2:01 PM
Subject: Re: RE: [TCML] mmc cap protection by spark-gaps-any ideas?


That was what I was trying to say. Some MMC designs I have seen use an over 
volt gap over the entire MMC to protect it. -- are you saying this is a bad 
idea? mike hammer used this design and it proved reliable for him. 
personally I have never used it. The caps i use allow me lots of breathing 
room. CDEs are simply awsome!!
The resistors are safety for the operator. Like I said it is a waste of 
energy and $$.
You can simply discharge a gap with a discharge wand after the power is off.


----- Original Message -----
From: S&JY <youngs@xxxxxxxxx>
Date: Monday, August 18, 2008 12:26 pm
Subject: RE: [TCML] mmc cap protection by spark-gaps-any ideas?
To: 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx>

> 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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