Re: Introduction / LTR caps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Mddeming@xxxxxxx 




In a message dated 9/6/05 11:20:51 A.M. Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:
Original poster: "Mark W. Stolz" <mark_w_stolz@xxxxxxxxxxx>

I would have to disagree.  The 10kVA coil we recently built uses a
.130 nF MMC and has had no problems, even with several minute runs.

Mark Stolz
http://teslacoils4christ.org/

>Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
>Don't use with pigs.  With a .05 uF Maxwell cap on a pig powered
>coil we measured 2,300 Apms peak on pri ---- too much for MMCs.
>
>Dr. Resonance



     While both of these answers are correct under their own 
conditions, the lack of specificity and explanation, while  to 
establishing a point of view, provide little or no insight.
Actually, it all depends on how the MMC is made. Describing an MMC as 
130 nF says nothing about its construction, voltage, or current 
handling capabilities.

Consider a single hypothetical cap rated 130nF. 600 VAC ,1500 VDC, 4 
A(rms), 200 A(peak).
    Now put four of them in a 2X2 array and you have an MMC that is 
still 130nF, but rated 1200 VAC, 3000 VDC, 8 A(rms), and 400 A(peak).
    Put 16 of them into a 4X4 array and you still have a 130nF MMC, 
but now its 2400 VAC, 6000 VDC, 16 A(rms) and 800 A(peak).
    Put 64 into an 8X8 array and you STILL have a 130nF MMC, only 
now its 4800 VAC, 12000 VDC 32 A(rms) and 1600 A(peak).
    Put 144 into a 12X12 array and you still have a 130nF MMC but at 
7200 VAC, 18000 VDC, 40 A(rms) and 2400 A(peak).

    The capabilities of an MMC depend entirely on how the total 
value is made up. In general, if you have a supply of caps of 
capacitance C, voltage rating V, and peak current A, then putting 
them into an M caps by N strings array will result in an MMC with the 
following charactistics:

Capacitance=CXN/M
Voltage=VXM
Current=AXN

There is, of course, a practical upper limit on the numbers M & N caused by:
1) resistive circuit losses (ESR, etc.)
2) Physical board size and volumetric heat dissipation.
3) Cost (MXN gets big very fast!)
4) Component reliability in very large samples.

So, can one make an MMC to work with a pole pig? YES
Will the MMC you tailored to your NST die in pig service? Most likely.
Before moving up to pig power, you really need to know all the 
internal specs of your caps.

Hope this helps clarify things,

Matt D.