Re: acmi and mandk sources anyone?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

Peter Lawrence wrote:

> I've built four coils with the same overall dimensions
...
> 1)  6 turns #2 wire, 2-tpi  495 turns #24 wire, 45 tpi
> 2)  9 turns #6 wire, 3 tpi  759 turns #28 wire, 69 tpi
> 3) 15 turns #10 wire, 5 tpi 1287 turns #32 wire, 117 tpi
> 4) 24 turns #14 wire, 8 tpi 1993 turns #36 wire, 181 tpi 

Had to guess a few things, but I've modeled your coils #1 and #4,

      tap   k      peak gradient     at          mode3
#1    1.7   0.16      930 V/m       22% height     4%
#4    5.7   0.17      205 V/m       35% height     3%

where the tapping points are given in turns from the inside and you
are using the outermost turns.  Yours ought to be in the same
ballpark, give or take a turn.

The upshot is that there is no more than the usual small amount of
higher mode activity in these coils, typical of the small k factors,
so this can't be the cause of your racing arcs unless something else
is very different.  Are your actual tapping points vastly different
to my estimates?  Do the racing arcs appear before or after topload
breakout as you turn up the variac?  The modeling assumes a good
ground plane under the coil. 
 
The effective reactances of the secondaries come out at

      Les      Ces      Fres  
#1    5.5mH   12.2pF   615 kHz  
#4   90.3mH   12.3pF   152 kHz 

are your figures vastly different to these?

As far as acmi goes, there's nothing to suggest that it's more
accurate than MANDK - they both use a similar method. acmi is more
difficult to use because it's a more general purpose program - MANDK
is specific to TCs.  If you're a programmer you'll enjoy rooting
about in acmi's source. 

Cheers,
--
Paul Nicholson,
Manchester, UK
--