RE: center tapped transformers

["Tesla list" <tesla@xxxxxxxxxx>]

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

There is not a consensus on this question, and there are valid reasons
for both configurations.

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. And I don't think the safety angle carries
any weight as you shouldn't ever be touching the NST when the coil is
powered.

If the NST mid-tap is wired to the RF ground, there may be a very high
RF potential between RF ground and mains-ground (neutral wire), and it's
been suggested that the NST primary insulation may at risk.  But should
there be a streamer strike to the primary coil, it would be safely
channeled to RF ground.  While the potential across the NST
primary-to-core insulation is worrisome, I've never heard of an NST
failing for a primary side failure.  But the devil's advocate must ask -
if there was primary-to-core leakage, would that even be detected?  It
could elevate the RF ground to a mains fault condition.

I personally use the RF ground connection, but I acknowledge that
neither is perfect under all scenarios.

Regards, Gary Lau
MA, USA




> Original poster: "Langer Giv'r" <transworldsnowboarding19@xxxxxxxxxxx>
>
> when you ground the mid tap, do you earth ground it (rod into the
> ground) or do you ground it with your house?
> Thanks
>
>
> >From: "Tesla list" <tesla@xxxxxxxxxx>
> >To: tesla@xxxxxxxxxx
> >Subject: Re: center tapped transformers
> >Date: Wed, 02 Nov 2005 21:34:12 -0700
> >
> >Original poster: FutureT@xxxxxxx
> >
> >In a message dated 11/2/05 4:22:09 PM Eastern Standard Time,
> >tesla@xxxxxxxxxx writes:
> >
> >Q,
> >
> >The secondary insulation of NST's and OBIT's cannot withstand
> >the voltage stress of what you're suggesting.
> >
> >John
> >
> >
> >>Original poster: "Qndre Qndre" <qndre_encrypt@xxxxxxxxxxx>
> >>
> >>There is a question I asked myself over and over again since the
> >>first time I've seen a schematic for a Tesla coil on the net: Why do
> >>coilers ground the center tap of the secondary of the high voltage
> >>transformer (NST or OBIT) instead of just doing the opposite
> >>(insulating the case from ground very carefully or cut the
connection
> >>of the secondary to the case)? As far as I know this would be safer
> >>since touching one of the output wires (or being accidently
connected
> >>to one by a streamer) wouldn't electrocute you in this case since
the
> >>output terminals weren't hot in respect to ground.
> >>
> >>Regards, Q.
> >>
>