Re: Air core chokes?

To: tesla-at-pupman-dot-com
Subject: Re: Air core chokes?
From: lod-at-pacbell-dot-net
Date: Sun, 12 Jan 1997 12:01:18 -0800
Subscriber: lod-at-pacbell-dot-net Sun Jan 12 22:11:14 1997

Steve Falco wrote:

> I'd like to protect my neon with chokes and spark gaps as per the list.
> But, I don't know where to get the toroid cores I've seen mentioned
> on this list.  Is it possible to wind an air-core choke to get some
> protection?  I have a fair amount of #30 and #18 magnet wire at the
> moment.

An single-layer aircore should do fine; in fact it should have less
shunt capacitance than a toroidal design. The design that I have used
for neon xfmr service over the last 5 yrs consists of #26 wire wound on 
a 2" PVC SCH 40(white) form, with a winding length of 2.5".  #30 should
work as well, just a little harder to handle.  
One choke goes on each HV leg of the xfmr.

> Also, how do I set the gaps on a protective spark gap?  Just set it
> 'till it stops firing, or can I calculate what I need.  (12kv 30ma neon
> and probably about .005 uF main capacitance.)

I used to put safety gaps across the xfmr, but never saw them fire so I
stopped using them, with no ill effects.  If the choke is doing its job,
why do you need them?  The .001 uf cap sounds like a better idea.

-GL