I have touched the case of my 5kV@20mA NST many times
during Tesla coil operation.It doesn't hurt at all.
My NST case is mains-grounded,and Tesla coil is grounded
to water pipe in my house :-)
Dex
--- Gary.Lau@xxxxxx wrote:
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Subject: RE: [TCML] Main ground vs RF ground
Date: Thu, 19 Nov 2009 18:39:07 +0000
The only place for using the mains-ground is for objects that one
is likely to touch while energized. The purpose is in the event
that there is a short between the HOT line and the thing that one
might touch - to provide a path to ground so that the fault current
trips the breaker or fuse and neutralizes the threat.
In a Tesla coil, there should be no objects beyond the variac case
or control cabinet, that one might touch. Only the variac case and
control cabinet should go to mains ground, and the NST case must
not be connected to that. The NST case should be considered off-
limits to touching (it will hurt the whole time...). Unlike in a
neon sign application in a pizza shop where a customer could
reasonably make contact with the NST case, we and those under our
supervision, should NEVER touch the NST case or any other part of a
Tesla coil. It is dangerous by nature and will never be UL-approved!
Using both an RF and mains ground for things that are RF-hot (NST
case), is not conservative, it's just wrong and serves no purpose
as far as minimizing RF interference. One could argue that it may
make the coil safer should there be a fault, but doing so destroys
your effort to reduce EMI. The Terry filter schematic is 100%
correct.
Regards, Gary Lau
MA, USA
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of chuck
Sent: Thursday, November 19, 2009 11:47 AM
To: 'Tesla Coil Mailing List'
Subject: RE: [TCML] Main ground vs RF ground
"But since you are asking about NST's and the Terry filter,
if you are running a single low powered NST with a Terry Filter,
you may
not have too many issues to be concerned about, but if you are
running
multiple NST's, I would consider a separate RF ground to be
safe... "
Would I be correct to infer that using separate RF and mains
grounds would
the more conservative way to go? That is, while I run a low risk
using a
common ground with one or more NSTs, that risk is reduced if I use
two
grounds: a mains ground and an RF ground? If so, I need to alter
my Terry
Filter.
Shouldn't somebody issue a pen and ink change to the Terry Filter
schematic?
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf
Of BunnyKiller
Sent: Thursday, November 19, 2009 12:17 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Main ground vs RF ground
Hey Chuck...
In the majority of instances, the RF ( or secondary base wire)
should
have its own "RF" ground rod. Hooking the secondary base to the
"house"
ground can lead to problems with items that contain circuitry
boards...
and thats about everything as far as appliances go... computers,
ovens,
stoves, refridgerators, garage door openers, touch lamps ( the
kind you
touch to turn on) will eventually fall prey to the wrong grounding
techniques. But since you are asking about NST's and the Terry
filter,
if you are running a single low powered NST with a Terry Filter,
you may
not have too many issues to be concerned about, but if you are
running
multiple NST's, I would consider a separate RF ground to be safe...
Replacing the stoves controller board isnt cheap... ask me how I
know
about that one ;)
There are some instances in which the NST is wired with the case
ground
on the center tap of the unit... IIRC grounding the case and
secondary
becomes "weird"...
not too sure about this situation.... see if someone else has
that answer.
Scot D
chuck wrote:
Some coilers say that the NST may be grounded to the mains ground
and
that the secondary of the TC should be grounded to RF ground and
emphatically declare that the two should never meet. Others say
ground
is ground and it doesn't matter where the unit is grounded as
long as
it is grounded. The famous schematic of the Terry Filters shows
the NST
and the TC sharing a common ground.
So which is it? Should the Terry Filter schematic be altered? Or
not? I
hope for first lights by Thanksgiving so I need an answer ASAP.
asimov13647@xxxxxxxxxxxx
Stuck in the (now infamous)
23rd NY Congressional district
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