[TCML] Tesla Coil Output Hazards, Skin Effect?

[Bert Hickman]

Ed Phillips wrote:
> Ed --- can you give us a brief summary especially of the let-go / no 
> let-go points?
> 
> I was hit with a 15/30 back in 1962 and never forgot it. Hurt like H but 
> I only touched the wire with the back of my hand.  Had I enclosed the 
> wire with my fist things might have turned out differently.
> 
> Dr. Resonance"
> 
>    Ed asked the question.  "dwp" apparently read the paper.
> 
> Ed
> 
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A web accessible concise summary can be found on pages 4-11 of "A Guide 
to Electrical Safety" from the North Carolina Dept of Labor:
http://www.nclabor.com/osha/etta/indguide/ig18.pdf

An interesting graph (Figure 2 on page 4) shows the electrocution 
threshold (in mA flowing through the chest) for a typical adult versus 
time flowing through the body. The thresholds for a child may be 
significantly lower.

The following was extracted from the above paper:
"Based on the research of Professor Dalziel of the University of 
California, Berkeley, the effect of 60 Hz (cycles per second) of 
alternating current on the human body is generally accepted to be as 
follows:
• 1 milliamp (mA) or less—no sensation—not felt
• 3 mA or more painful shock
• 5 mA or more—local muscle contractions—50 percent cannot let go
• 30 mA or more—breathing difficult—can cause unconsciousness
• 50–100 mA—possible heart ventricular fibrillation
• 100–200 mA—certain heart ventricular fibrillation
• 200 mA or more—severe burns and muscular contractions—heart more apt 
to stop than fibrillate
• Over a few amps—irreversible body damage"

"Thus, we can see that there are different types of injuries that 
electricity can cause. At the 20 to 30 mA range a form of anoxia 
(suffocation) can result. This could happen in a swimming pool where 
there is a ground loop present (the drain at the bottom of the pool) if 
a faulty light fixture or appliance is dropped into the water. Current 
would flow from the light fixture to the drain, using the water as the 
conducting medium. Any person swimming through the electrical field 
created by the fault current, would be bathed in potential difference 
and the internal current flow in the body could paralyze the breathing
mechanism. This is why it is very important to keep all portable 
electrical appliances away from sinks, tubs and pools."

"Ventricular fibrillation generally can occur in the range of 50 to 200 
mA. Ventricular fibrillation is the repeated, rapid, uncoordinated 
contractions of the ventricles of the heart resulting in the loss of 
synchronization between the heartbeat and the pulse beat. Once 
ventricular fibrillation occurs, death can ensue in a few minutes. 
Properly applied CPR (cardiopulmonary resuscitation) techniques can save 
the victim until emergency rescue personnel with a defibrillator arrive 
at the scene. Workers in the construction trades and others working with 
electrical power tools should receive CPR training."

Above a few amperes, irreversible body damage can occur. This condition 
is more likely to occur at voltages above 600 volts AC. For example, if 
a person contacted 10,000 volts, I = 10,000/1,000 = 10 amps. This amount 
of current would create a great amount of body heat. Since the body 
consists of over 60 percent water, the water would turn to steam at a
ratio of approximately 1 to 1,500. This would cause severe burns or 
exploding of body parts. These are the types of injuries that you would 
normally associate with electric power company workers. They can also 
occur, however, when people accidentally let a television or radio 
antenna contact an uninsulated power line. Accidents involving mobile 
vertical scaffolding or cranes booming up into power lines can cause 
these types of injuries or fatalities."

The above paper implies that, although 30 mA NST may not provide a fatal 
shock to a healthy adult, it could cause suffocation and loss of 
consciousness. A sustained shock from a 60 mA NST might be fatal (from 
ventricular fibrillation) if the victim couldn't free himself from being 
part of the current path. Either shock would be quite painful...  =<:^o

Bert
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