[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] Tesla Coil Output Hazards, Skin Effect?



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

_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla


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
--
***************************************************
We specialize in UNIQUE items! Coins shrunk by huge
magnetic fields, Lichtenberg Figures (our "Captured
Lightning") and out of print technical Books. Visit
Stoneridge Engineering at http://www.teslamania.com
***************************************************
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla