Re: grounding question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi John,

On the schematic shown and as typical with NST's, the two output 
leads go directly to the each end of the primary coil. The primary is 
floating in reference to the secondary. This is because the center of 
the NST's hv winding is connected to the iron core that it's wound on 
which is also connected internally to the case. Also, the case and 
core are often connected to mains ground (there is sometimes debate 
on that particular connection). You are correct that the bottom 
secondary should go to RF ground and that the primary should not (in 
this case).

I prefer (a debate topic sometimes on the list) to connect the case 
ground to RF ground. Thus, my filters safety gap is fired to RF 
ground and not mains ground. I only connect Neutral and Hot to the 
NST from mains power. Some others use mains ground at the case and 
safety gap. Either will work, but if your house is wired as my own, 
then when the safety gap fires, the Neutral line throughout the house 
and everything plugged into the outlets would feel the brunt of the 
hv arc at the safety gap (this is why I chose RF ground to the case 
instead of mains ground).

Other transformer selections (PT's, PIG's, homebrews, etc.) often do 
not have their hv winding connected to the core or to their case. In 
those instances, one end of the primary can be connected to RF ground 
(same point as the bottom of the secondary coil). Thus, the two coils 
are "not floating" and have the same point of voltage reference. When 
doing that particular hookup, one side of the hv winding is connected 
to RF ground and the other to one end of the cap. The other end of 
the cap is connected to the primary winding (usually the outer 
portion) and the inner winding of the primary to RF ground. I know 
this hookup is out of reach with your particular transformer but I 
wanted to explain why some schematics show a primary connection to RF ground.

Take care,
Bart

Tesla list wrote:

> Original poster: John <guipenguin@xxxxxxxxx>
>
> I think I am going to build this simple NST protection filter for my 
> new coil. 
> <http://hot-streamer.com/greg/filter.htm>http://hot-streamer.com/greg/filter.htm 
>
>
> I see the center safety spark gap is grounded to the NST's chasse, 
> which is grounded to mains ground.
>
> Now, am I correct in thinking that I should NOT ground the primary 
> circuit to the same ground as the end of the secondary (as I see in 
> many schematics) as this could pose a threat from putting you in 
> contact with the primary circuit through a secondary spark?
> for a spark gap Tesla coil, is this circuit that I linked the only 
> thing that should be ground to mains ground?     and then ONLY have 
> the end of the secondary coil to a separate RF ground?
>
> I want to make sure I have everything as safe as possible before I 
> even start building my design.
>
>
>
> Thanks again,
>
>       John.