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Re: Fw: Grounding of HV Transformer.

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

Hi Christoph,

Tesla list wrote:

Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>

Hello Bart.

> Looks pretty cool!  If your using mains ground and have no RF ground,
> then every time you get a primary strike (or even when the current
> gets high), you can certainly be zapped. You need a dedicated ground
> for RF.
Of course I use a RF ground, but only for the base of the secondary at
this time, but that can be easily changed.

Ok, well, see. Not always.

> Tie the core (sec) to RF ground. Your inner primary and
> bottom secondary should also be tied to RF ground.
Does this mean additionally to RF ground, connecting mains and RF ground
at the transformer?

Do not tie mains ground to RF ground. Mains ground should end at your controls. In order to tie the inner primary to RF ground depends on your transformer connections. For an NST, it would be typical to float the hv output across the primary with the cap in series. This is because the hv side of the NST is grounded to the case. Not so with your homebrew transformer, so you are free to set it up anyway you want.

One end of the primary must be mains ground, as there
is noe isolation transformer between mains and HV xformer input.

Hmm, this concerns me. Are you connecting 120 Vac to the transformer with one end grounded (or neutral and ground are one and the same in your house)? If so, don't tie the primary to RF ground. All your doing at that point is allowing RF to ride on mains ground. Instead, just float the primary (treat the mains ground as an opposite polarity to the AC line, like neutral). Is it possible your case is connected to this same ground point?

Here's a theory; whenever you get a primary strike, the hv induced on the primary is felt at the transformer core or case, finding it's way back to mains ground and on to the controller where you are getting zapped.

I have a question, is one of your hv winding ends connected to the case? or at a similar reference point? or are they completely isolated from the core and case?

Or are you referring to the TC itself with "inner primary and secondary"...
I guess so... so I will have to move the cap from one end of the RSG to
the other to get the connections right.

The primary can be moved to RF ground "only" if the transformer is also capable of grounding one side. I wouldn't change anything yet. Let's get it figured out first. It seems that you either have a hv winding at case/core ground or you may be arcing to the core during those primary strike events internal to your hv transformer. Just to let you know what is the norm, I never get a shock during major primary strikes, even long lasting primary strikes. We just need to find out where it's coming from.

Take care,