Re: MMC Design and Wiring

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Conner <steve@xxxxxxxxxxxx>


> Should an MMC be wired so that the current flows in opposite directions
> in adjacent capacitors in a series string(to reduce inductance in the
> primary circuit)?

As far as I know, that was something I came up with when I was 
working on OLTCs. They typically have a primary inductance less than 
1uH, so even a couple hundred nanohenries of stray inductance can 
hurt performance.

On a spark-gap coil (or a DRSSTC for that matter) the primary has a 
much higher inductance, so the inductance of your cap bank can be 
ignored, unless you decide to make a 40 foot long capacitor or something.


>Can I place the strings in close
> proximity to one another without danger of arc over between strings?

I put mine pretty close:

http://www.scopeboy.com/tesla/newcapsnewdanger.jpg

This was a MMC cap rated at 12.5nF, 22kV, with four strings of 15 
caps. I used it in a DC resonant charging coil with a DC bus voltage 
of 10kV, and never had any trouble. Each cap has a 10 Meg VR37 
bleeder resistor across it. The picture is from this page:

http://www.scopeboy.com/tesla/t21m.html

Unused strings are a different matter altogether, though. They need a 
lot more clearance.


Steve Conner
http://www.scopeboy.com/