Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
Hi all,
I may as well jump in and throw in my two-bits worth ;^)
I have not experienced shocks IF the primary capacitor
was in parallel with the HV secondary winding of the po-
wer transformer AND properly RF grounded.
Where I have had a little problem is
when I "float" the capacitor where both sides of it are
"hot" and it has no direct connection to the RF ground
once the coil is de-energized. That allows an electrosta-
tic charge to remain on the metal case surface of my
50 kV, .1 uFd Hipotronics pulse cap in my Green Monster
coil: http://www.teslauniverse.com/members/drieben/
(the turqouis green box with the insulator bushing)
I never received any severe shock because of this, it
was more like the shock from rubbing your feet across
a shag carpet and touching a doorknob on a cold dry
winter's day. However, it was still rather startling and
once I rewired the circuit for the cap's case to always
be tied to RF ground, this problem disappeared. There
is a residual charge left in the filter caps of my VTTC
caps after power down, though, and the discharge
looks hot enough to be very harmful or lethal!
It's kind of funny that >10J is considered lethally
dangerous and yet paramedics typically use 200J
and sometimes even 360J to "restart" a heart that
is in fibrillation. BTW, fibrillation does not mean that
the heart is completely STOPPED. Instead, it referrs
to a jelly-like quivering that the heart goes into when
its beat rhythm is knocked out of synch for whatever
medical reason. The heart cannot effectively pump blood
in this manner and death will soon occur if this beat
rhythm is not restored. The defibrillation cap discharge
actually resets the electrical rythym to (hopefully) restore
the natural heart beat rhythm. I think Peter Terren is an
actual medical doctor and he can probably explain it better
than my firefighter/rescue training allows me to explain it.
I think as little as 10 mA across the heart can cause fibril-
lation (which is obviously lethal if not quickly corrected)
but I believe it takes considerably more current to complete-
ly STOP the heart (seems like I've heard several hundred mAs)
If the heart is completely STOPPED by electrocution, I don't
think defibrillation will be able to correct that. It's all over!
Let's all be careful,
David Rieben
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, February 20, 2007 10:55 PM
Subject: Re: The MMC debate continues . . . . . .
> Original poster: Sparktron01@xxxxxxxxxxx
>
> Hi DC, Ed
>
> SNIP
> -------------------------------------
> > The two paths from the nst to it's center-tapped ground, the winding
> > resistance is perhaps 10K at maximum. Using a 5RC time constant the
> > reduces the cap discharge time to under 10 seconds for most small and
> > medium nsts with their respective small cap bank values. Perhaps
> > this is why our coils have never shocked anyone. We always run on AC
> > and never DC. Also, at higher potentials, the small dia of the cap
> > leads and any single sharp point on the cap bank board will bleed off
> > charge as corona in much the same manner as a high potential Van de
> > Graaff generator, even with it's symmetrical well-rounded terminal,
> > will bleed off over 400 kV into the ambient air, without being
> > discharged with a ground wand, in under 60 seconds. The MMC caps are
> > at much lower potential but with their nst resistance path directly
> > to ground and any slightly sharp point on the cap board or
> > connections dangerous potentials are quickly bled off
> ---------------------------------------------------
> Only time I was shocked was while working with a PT powered Tesla
> Equidrive configuration. At high power (IMHO), the caps ARE NOT
> perfectly balanced. This will lead to an unavoidable voltage delta
> between the two sides. Even with a 5% imbalance with 14kVrms
> (typical) would result in ~1kV (20kVpk *.05) available in series circuit ;
> and up to several times that amount could be dynamically transfered
> based on SG operation etc. I know on Ed's magnifier, easily 5kV or
> more has been seen when the caps are discharged (guess, never been
> measured). Richard Hull's 20kV magnifier 11E and Alex Tajnsek's
> "dynamite" magnifier also had to be manually discharged. Note that
> Richard's machine, one side of 20kV PT's was tied to ground; and
> ground path did not impair C delta charge build up.
>
> As an additional footnote, I also have never been shocked by NST powered
> TC's with equidrive circuit. Also additional footnote: National Electric
Code
> 1999 and later editions, Article 665 (Dielectric/Induction Heating).
> Paraphrasing: All capacitors 0.1uF or larger operating at voltages of
> 240V or more WILL have bleeder resistors installed. This includes
> VT bias or keying (modulation/staccato control) power supplies.
>
> 0.1uF @ 250VDC ~ 0.003J (3 millijoules). This level probably
> chosen due to involuntary startle reaction resulting in secondary
> injuries (lacerations/cuts) or throwing limb onto HV or power circuits
> which could result in additional severe / lethal trauma. 3mJ is not
> trivial, IT HURTS!!! 10J and above is generally considered a
> LETHAL hazard.
>
> Regards
> Dave Sharpe, TCBOR/HEAS
> Chesterfield, VA USA
>