Re: center tapped transformers

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>


> Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

> RF ground is what the secondary base is tied to, and should go to a
> ground rod separate from the mains-ground.

> If the NST mid-tap is wired to mains-ground, the NST core (connected
> internally to the mid-tap) is at the same potential as the
> mains-neutral.  The NST case is safe to touch (the main reason cited for
> connecting it to the mains-ground).  But if there should be a streamer
> strike to the primary coil, the safety gaps (you have these, right?)
> will fire, channeling the streamer current to the NST case and into your
> mains-ground.  Not healthy.

    X1

   ||O--------------------------------nnnnnnnn--TO-TANK-CIRCUIT->
   ||O            |             |        RF1
   ||O         ------- BC1      |
--O||O         -------          |
  O||O            |             *
  O||O--|--RRR----|-----GRND----* SSG
  O||O  |         |             *
--O||O  |      -------          |
   ||O  |      ------- BC2      |
   ||O  |         |             |        RF2
   ||O--|------------------------------uuuuuuuu--TO-TANK-CIRCUIT->
        |
        |
   mains GRND

SSG - safety SG
RRR - total impedance between mains ground and RF ground

as you said above, secondary base is tied to GRND, not mains GRND, so
when a streamer strike the primary coil and the safety gaps fire, all
HV will be across the RF1 & RF2, as they have much more impedance for
RF than closed SSG.
as a result chokes insulation will break down and HV through SSG would
go back to the secondary base - how could it go to the mains GRND?

in order to significantly increase the voltage on the mains GRND, RRR
impedance must be much more than impedance of the secondary winding of
NST - is it the case in reality?

the impedance of the closed SSG is smaller than the streamer
impedance (or even power arc, as the length of the power arc is more
than the arc length is the SSG), so insulation between NST HV outputs
and its case wouldn`t be destroyed i guess, then the potential of
mains GRND will not increase.

so what`s the trouble?

-----
Neon transformers are doomed in Tesla service! I should know, I've
killed more of 'em than many pople have ever even seen in a life time.
25-03-96 (c) Richard Hull, TCBOR