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Re: [TCML] Alternative RSG Motor and shielding
On 8/29/13 5:15 AM, Mark X2 wrote:
Had to dig into the archives, but when it comes to TC grounding,
I find this thread by Richard Quick very valuable:
http://www.pupman.com/listarchives/1995/november/msg00132.html
quote:
"You build or find a heavy ground and you ground your coil system
to it. The connections made to this RF ground are as follows:
SECONDARY COIL, SAFETY GAP, STEP UP XFRMR CORE, BYPASS CAPACITORS
(if using a center tap grnd xfrmr), SPARK GAP MOTOR HOUSINGS,
SPARK SHIELDS, AND ANY OBJECT SUBJECT TO BE STRUCK WITH DISCHARGE
You don't need a heavy ground, but the general point is that all these
things need to be tied to the "cold end" of the secondary. You want
secondary spark current to go to back to the secondary, not through your
gear.
I don't usually use my caps lock, but this is important. This
technique prevents RFI complaints, and will save valuable
electronic equipment in your area from destruction. It may save
you from the last shock of your life.
You ground your variac housing to your neutral wire.
*DANGER WILL ROBINSON*
NEVER connect the case of anything to the power line neutral. It's the
"grounded" conductor, but not the "grounding" conductor. There's no
guarantee that it's actually at a safe potential. Connect the housing
to the "green wire" ground.
All other
coil controls, relay housings, control xfrmr cores, line RFI
filters (run backwards) are grounded to the variac housing. Strap
is taken from the variac housing to a well grounded water pipe.
This protects the coil operator and the control circuits from
kickback that may come down the line from the step up xfrmr.
Water pipes are not a good ground, any more. Too much plastic, etc.
But basically all things you can "touch" or that are "line voltage
related" should be tied together to "green wire ground". Bear in mind
that more ground wires forming parallel paths is not a good thing. One
ground wire to each thing, forming a nice tree.
Two 60 cycle cables are run from the variac, through reversed
line filters, out to the step up xfrmr. No ground connection is
made anywhere between the 60 cycle cabinet ground and the RF
system ground. Hot wires only are given to the primary of the
step up xfrmr, as well as any gap motors or other utility for the
coil tank circuit.
Yup..
Although for safety purposes, connecting RF ground (if it's things you
can touch) and green wire ground is necessary. If you have an RFI
problem, that connection could be through a RF choke. It's the line
frequency current that is an issue. (e.g. a spark connecting the primary
winding and the RF ground is like hooking the output of your pole pig up
to the RF ground, and if you're touching the RF ground and something
else at the same time, you'll be fried.
This is called the "two ground system" and it is highly recom-
mended. The idea of the two ground system is to send all of the
RF to a dedicated ground, and prevent bleedover into your house
wiring, control cabinet and/or water pipe. It also protects the
operator with two low potential grounds from the lethal possi-
bilities of a coil misfire or similar "incident"."
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