[TCML] Tesla Coil Output Hazards, Skin Effect?

[Frank]

Here is a direct copy of the hazards from the 
book by Fink. All can read it and see he did not 
say it was not dangerous to take a shock from a 15k transformer!

"Electrical Protection for the Sign 
Installation.-Simple as a luminous tube is, it. 
must be realized at all times that it is 
potentially a very dangerous piece of apparatus. 
'When properly constructed and installed, it 
presents less hazard than an ordinary lamp 
socket. But if proper precautions are not taken, 
the high voltage used is definitely dangerous. 
Since the current is limited to 30 or 60 
milliamperes in most cases, the neon sign usually 
cannot produce a shock of sufficient force to 
kill a man. But the shock from a neon sign is 
powerful enough to overthrow a man, and the 
resulting fall may easily kill or cripple him. 
Furthermore, the possibility of the public's 
coming in contact with the high voltage is far 
too great a hazard to be allowed. "

In most cases, a shock from a NST is usually from 
one side of the transformer to ground so the voltage is 1/2 the rated.

Potentials that can kill vary a lot depending on 
the human physiology, the current path thru the body and conditions.
The better the conduction path, IE, your are wet 
or even better, sweating, the lower the voltage is needed.

There are many documented cases of personnel that 
took a shock from a HV source and even lightning 
and walked away only to die a few hrs / days 
later. They were found that have damage to 
internal parts from the path the current took.

I know of a welder that got electrocuted when he 
accidentally struck the side of his face with the 
stinger. He was wet, salt water was around, the OCV was 70 VDC.

Heart stimulators are not high voltage items but 
high current. Using conductive gels and proper 
location of the paddles, it saves lives. It can also stop a heart.

Once you get past the skin, very little voltage 
can kill, look at a pacemaker for example. It 
uses very minute voltages to control or even shock the heart.

Properly applied a 9 V battery can kill!
In the tube days, ham radio operators were killed 
with voltages around 500 to 1000 VDC and 1-2 amperes.

A good rule of thumb is to touch a suspected live 
circuit with the back of your hand, that way you 
will not involuntarily grasp the circuit if it is 
live. keep one hand in your pocket to minimize 
the circuit path across the heart.

NEVER wear any metal, rings, watches, earrings, 
bracelets or necklaces when working around 
electricity, especially HV. Be aware of your 
pants and the buttons on them. Jeans usually have 
a metal button and you can complete the circuit 
from your hand thru your belly if you are leaning 
against a grounded or metal object.
Even low voltage, say like a car battery, can 
burn the skin around the metal object if it is 
shorted. A ring across a car battery will spot 
weld itself to the connections and then the ring 
gets red hot and you can lose a finger.

With Tesla or RF currents, current density is 
particularly important. These devices put out a 
pretty much fixed current and if concentrated to 
a small area, nasty burns or damage can occur. If 
spread out over a larger area, chances are there will be no damage.

The early diathermy machines were spark gap Tesla 
devices and they would put up to 5 amps of RF 
current thru a patient using electrodes that were 
metal with wet sponges in direct contact with the skin.

Early electrotherapy used large static machines 
capable of 12" or more sparks and patients were 
directly across the output at times. Extremely HV 
DC and microamperes of current.

It is basically the combination of voltage and 
current that is lethal and mainly current. The 
higher the current, the higher the risk.

In large TC's that use a pole xfmr, one is at a 
very high risk of electrocution it getting across 
the secondary circuit of the transformer.
NST coils are dangerous too, do not get me wrong, 
and ALWAYS proper caution is to be used around these devices.

Frank


At 11:36 PM 12/1/2007 -0600, you wrote:
>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
>
>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
>• 50­100 mA—possible heart ventricular fibrillation
>• 100­200 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
>--