# [TCML] MMC

bartb bartb at classictesla.com
Sun May 10 10:45:40 MDT 2009

```Hi Mitch,

no big deal. Given cap tolerances, you would end up up with some
variation no matter what. But there is some confusion here. You stated
"20 x 0.47uF". Did you mean 0.047uF? 2 strings of 10 using 0.047uF would
give you 0.0094uF. 2 strings of 0.47uF would give you 0.094uF.

Next problem is transformer resonance. Because you are looking at
.0095uF for a 10/30 NST, then I assume your in 50Hz land. This is the
capacitance at which the NST will become resonant. This resonance can
cause excessive voltage at the caps damaging both the caps and even the
NST itself. We often recommend going 1.5 x Cres for static gap coils,
thus, you should be building for 0.0143uF.

Another problem is the MMC standoff voltage. For your 10kV NST, the 10kV
is an rms value. The NST and MMC will see the peak voltages of a little
over 14kV. Your cap should be designed for at least the peak voltage at
a "minimum" and preferably 2X the peak voltage.

Undersizing the cap standoff voltage and also designing for NST
resonance is a good way to kill your caps and your NST quickly.

Take care,
Bart

Mitch Newman wrote:
> Hi all,
> As some of you may know, i am new to the Tesla world.But i wanted to know, because some of the materials used in the Tesla coil can be hard to find i just wanted to know if i could use "20 X 0.47 uF / 1000 V. METALLISED POLY AXIAL CAPACITORS" set up in 2 stings of 10 (caps) set up in parallel, to reach the 0.0095uF, 10kv that the output of a 10kv, 30ma, NST.but the NST needs 0.0095uF for the capacitors but, using the MMC calculator on "DeepFriedNeon.com" the capacitance of those capacitors wired up in two strings in parallel (10 caps each) it comes to 10kv and 0.0094uF.
> Will that make a major problem being the capacitance off by 0.0001or will it be fine like that ?
> Thanks heaps,Mitch ~ Gb
```