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Re: [TCML] NIST High Voltage Laboratory Testing / Safety Reference

As to using the water service as a ground, I also have all copper in the house, but a PVC service line to the meter, so using it could be shocking to someone in the house using a sink or shower.

One thing to be aware of, is many utilities (I retired from a county water/sewer dept.) are using smart meters, which may not like induced voltage on them. My service entrance has a dedicated ground rod, which I call "line ground" on my schematic. My RF ground is a single ground rod located close to where I run the coil. I have a welding cable disconnect to connect the FAT welding cable to the coil and a smaller 2 AWG one to go to the pig and lightning arrester.

 From: Jim Mora <wavetuner@xxxxxxxxx>
To: 'Yurtle Turtle' <yurtle_t@xxxxxxxxx>; 'Tesla Coil Mailing List' <tesla@xxxxxxxxxx> 
Sent: Saturday, August 23, 2014 2:50 AM
Subject: RE: [TCML] NIST High Voltage Laboratory Testing / Safety Reference


Nice layout. My control cabinet (well bonded to ground) is similar though
presently I only need one manual power stat. (I have two more off shaft).
Its all in a half high 19" rack mount enclosure with a read door. I also use
a smaller variac to supply rectified DC to a saturable reactor I pulled from
a big Blue Ox oven. I sold the 25KVA monster I used to have. I included a
dead man switch on the key switch line. It's just a cotter pin activated
microswitch attached to the operator via monofilament and an alligator clip.
So if knocked out or worse the system shuts down to protect first
responders. I pull the cartridge fuses too, and check for them in my pocket
if I'm near the pig.

There are interlocks on the doors but as a former support technician in the
field, it was always necessary to defeat them somehow to make repairs,
schematics on hand. Most of what I did was LV. Some are cleverly well hidden
by design engineers. I don't see Tesla Hobbyists as using them unless they
have a HV cabinet in the near vicinity. Who would get their head in there
without locking out the safety switch? Mine is a Big dude with big knifes
and long travel.

My electrical is on a big breaker in the main service entrance and feeds a
dedicated subpanel near the cabinet. I'm fortunate; my house has all copper
water pipe. I use two ground rods at the service entrance in addition and
have 3/4 copper feed pipe coming from the water meter near the street under
the sprinkler system. It is pretty much a star ground otherwise.

RF ground is of course separate and at a distance in the back.

Jim Mora

-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of Yurtle Turtle via
Sent: Friday, August 22, 2014 6:43 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] NIST High Voltage Laboratory Testing / Safety Reference


This is my work in progress. I haven't updated it in quite some time. I
think the only thing that's missing is the dedicated 100 amp breaker, and
the line filters. It's probably not what I would have done from scratch, as
it has evolved. Anyway, suggestions/comments are welcome.

From: David Sharpe <sparktron01@xxxxxxxxx>
To: Tesla Coil Mail List <tesla@xxxxxxxxxx> 
Sent: Wednesday, August 20, 2014 7:09 AM
Subject: [TCML] NIST High Voltage Laboratory Testing / Safety Reference

Truly excellent reference for use when designing
medium or high voltage equipment or performing HV lab work,
from NIST.  This document was referenced in a recent
EDN e-blog.  The great thing about this document is it
is succinct, brief (9 pages), specific, and to the point.


One recommendation is the requirement of having "2"
separate operations to turn on high voltage; this requires
at a minimum a Main Disconnect (Lockable Safety Switch)
and a start-stop push-button station with seal in contactor.
This requirement supports my contention you should never
"instant on" high voltage equipment.  YMMV, but I've seen
catastrophic, spectacular failures doing this.

The additional requirements of a RTZ (Return to Zero) interlock,
on all  HV equipment is very interesting, and I'd bet less then
5% of the amateur Tesla Coil HV equipment built worldwide
has that feature.  But RTZ could save your life, and possibly
infrastructure too.  I am designing a solid state power controller
with integral ballasting and current limit regulation (240V/100A)
utilizing AC Chopper technology that I have decided to incorporate
this feature into the design.  An additional requirement is a
flashing red beacon with the presence of High Voltage (if it
doesn't interfere with testing).  If the SG is not firing, you have
no outward indication that there is high voltage present, which could
have very dangerous consequences.

I hope this document is useful to the Tesla Community

Best Regards

Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA

Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
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