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Re: NST Safety Gap Question.
At 11:27 AM 17/04/00 -0600, you wrote:
>Original Poster: "William Parn" <parn-at-fgm-dot-com>
>
>
>Greetings All,
>
>I picked up a second 9kv-at-30ma NST and decided that
>I now will definitely need a safety gap. So I
>hooked one up and paralleled the NST's. The gap
>constantly fired, it did not fire when connected
>up to one NST directly. So I doubled the spacing
>of the gap and then it still fired often.
>
>So I am wondering what are the basic rules for setting
>the safety gap so that it only fires upon a primary
>strike, or something potentially equally devastating?
>
>Or does it sound like I maybe have another problem, like
>maybe to small a wire in the primary hookups?
>
>By the way my variac is electrically tingling me
>with the two NST paralleled. Will this stop if I
>stop using the house ground for the NST's and variac?
>
>Many Thanks,
>Bill Parn
>
Hello Bill:
The simplest and most effective way to set the safety gaps is to connect
them, and only them, to your transformer(s) and set the gaps close.
They will fire initially, meaning you need to increase the gaps slightly
and equally and try again. Repeat this until you find that magic spot
which is just beyond the point where they fire. Secure them at this
spacing and you're all set.
Regarding the "tingling" off your variac, this indicates that it is hot
with R.F. or possibly a ground fault exists. Make sure that your T.C.
secondary bottom, your center terminal of your safety gaps, and the
cases of your N.S.T.'s are all connected together and to a GOOD ground
separate from the third pin ground of your power cord. The ground wire
of your power cord should be connected to the metal frame of the variac,
any metal parts of your control panel, and the ground terminal of your
E.M.I. line filter only.
73, Weazle, VE3EAR/VE3WZL
Listening: 147.030+ and 442.075+
E-mail: weazle-at-hurontel.on.ca
or ve3ear-at-rac.ca
Web site: www.hurontel.on.ca/~weazle