Re: secondary coils

["Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Kevin,

Comments interspersed below.

> Original Poster: "Kevin Wahila" <knw2-at-lehigh.edu>
> a few questions to help ease the mind (mine)
> how do i decide which size secondary to use with my system? i have
> both a 4" and 6"  i have 3 9kV 30mA neons as a power supply.

Personally, I donīt think the secondary size vs. transformer rating is
THAT critical. Of course, it would be pointless to run a 10kVA pole
pig on a 2" secondary or a 4kV/30mA NST with a 20" secondary,
but for all practical purposes, you can use either one. If you plan on
upgrading your psu someday, go for the 6". If you are more or less
"fixed" to the above NSTs, there is no real reason why you canīt
use the 4". Depending on true construction, the 6" will allow you to
go for a lower Fres. This means you can use a bigger capacitor in
the primary tank circuit (longer sparks).  Can you give us some
more specs on the secondaries (i.e: wire gauge, winding length)?

> i am also wondering what there really is to gain by using 1, 2 or all
> three of them.  in a unit as small as mine, is it worth adding them
> or just going for the best with one?

This depends on your setup. Are you using a static gap or a (sync)
rotary? What cap size, Fres, etc are you planning to run? In other
words, if your setup (primarily dependant on cap size (and Joules)
is small enough, so that one NST (270VA) "fills the bill", then there
is no point in using all three. However, if you are (like most) chasing
after the longest possible spark, you will want to use all 3 in parallel
(9kV-at-90mA = 810VA). Match the caps to the xformer rating for the
highest possible Joules. This includes the possible useage of LTR
(larger than resonant caps), etc. Build your coil so that it will take
full use of the input power (large enough toroid, etc).

> about MMC's, either i am confused (well that is a given i guess) but
>when people use these as primary caps, have i been noticing that
>the overall  voltage rating they chose is not the typical 50kV rating
>one would try to use when doing a poly cap. but rather much less?
> how come?

Have a look at my long post called "Re: Another MMC cap
candidate (UK)" for MMC designing tips. You can find it in the
archives. In a nutshell, tho: The typical 50kV rating for rolled
poly caps is necessary, because you are using non virgin,
non uniform thick materials, that are touched and rolled by
human hand (i.e: YOU). The MMC has a lot of edge here,
because we have the benefit of being able to use the
commercial manufaturerīs "state of the art" design. They use
virgin material and machines to roll the cap. This makes each
cap very strong, so there is no need to "over do" it on voltage
rating (i.e: the safety factor with MMCs is much higher than
the printed rating will let you believe and much, much higher
than a self rolled cap).


Coiler greets from germany,
Reinhard