RE:Tesla Coil Grounding (was - Pig setup help.)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John H. Couture" <couturejh-at-mgte-dot-com> 


All -

To my knowledge all safety codes regarding the grounding of power
transformers say the transformer case should be grounded to the green wire
as defined in the codes.
The main grounding question for Tesla coils is the connection of the green
wire network to the secondary circuit (so-called RF) ground. Apparently
coilers do it both ways, some connect and some do not connect. There are no
codes for this type of connection. From a safety standpoint not connecting
the two could be a hazard to humans. If you are taking sparks from a small
or medium TC the line voltage could kill you if there is a spark between the
primary and secondary coils.

John Couture

----------------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, March 15, 2004 10:05 AM
To: tesla-at-pupman-dot-com
Subject: Re: Pig setup help.


Original poster: Bart Anderson <classi6-at-classictesla-dot-com>

Hi Gerry,

Tesla list wrote:

 >Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >Hi Bart, John and others,
 >
 >This issue of whether to ground the transformer case (whether it be a pig
or
 >NST) to mains ground or dedicated RF ground seems to be a reoccuring
 >question that I think has no right or wrong.  I know there are opinions on
 >both sides and valid ones.  Each solution has its benefits and problems and
 >how one treats this issue depends on how they define their system.  The
 >following are the benefits and problems as I see them:
 >
 >Transformer grounded to mains ground (green wire):
 >
 >Benefit:  transformer fault (like primary to case short or secondary to
case
 >short) may draw excessive current and blow breaker (note that the balast
for
 >a PIG or PT may not allow this to happen unless ground fault protection is
 >used).  Case is safer, however one still has the bushings that can kill.
 >
 >Disadvantage:  A strike to the TC primary (transformer secondary) could
 >flashover to the case and thus the mains ground and kill sensitive
 >components (TV, stereo, etc) also plugged into the mains.

It is possible, but this is true with both configurations, including
floating configurations. The lowest impedance will feel the brunt of the
hit. Also, consider strike rings tied to rf ground (for all those folks who
use them).  A probability factor comes into play by an increase frequency
of hits (and you will get an increase in primary directed hits if a strike
ring is used, and at times, the primary will get hit as well (especially
for coils with poor field control). I just prefer to minimize the
possibility's.
Take care,
Bart

 >Transformer grounded to dedicated earth ground (aka RF ground):
 >
 >Benefit: a strike to TC primary that results in flashover to transformer
 >case will directly return to the secondary ground and not contaminate mains
 >power.
 >
 >Disadvantage:  transformer fault could result in a HOT case and no blowing
 >of the breakers if the dedicated earth ground is not adequate.  If
adequate,
 >the protection should be just a good as mains ground, but still no
 >guarantees for the balasted pig or PT unless ground fault protection is
 >used.
 >
 >I think one should define danger zones in their system design.  If the
 >transformer is within the danger zone,  grounding to the dedicated earth
 >ground is OK.  If outside the danger zone, the transformer should be
 >grounded to mains ground and the bushings protected from accidental
contact.
 >
 >One persons opinion,
 >Gerry R