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Re: [TCML] difference between 10 mA from a flyback and a low voltage PSU ?



Alphonse,

The output of a flyback system is high frequency alternating current, probably in the range of 15 - 60 KHz. It is unlikely that you can come across an ordinary flyback transformer that could produce a continuous 300 watt output. Flybacks were used to power cathode ray tubes, which required high voltage but very low current. If you are drawing 10 mA from your flyback system, the output voltage will probably droop significantly. Say you are driving it with 12 volts, you would have to be feeding in at least 25 amps of supply current to get 300 watts. In reality, you would actually need a lot more, since no conversion system would be 100% efficient. You will have to be using some beefy power transistors to drive it at that power level.

Another responder mentioned the skin effect, in which high frequency alternating current tends to flow across the surface of a conductor rather than passing through the entire conductor. In the past, many TC operators thought that the skin effect would protect themselves from damage caused by the outputs of their coils. However, recent analyses previously posted in this list have indicated that your body would have to be ten feet thick (3+ meters) to obtain any appreciable protection by the skin effect at the frequencies commonly encountered in TC work. Therefore, don't count on the skin effect to provide you with any effective protection from high voltage RF current.

High voltage RF will burn painful black holes in your skin that take a long time to heal. In surgery, we routinely use RF electrocautery systems to simultaneously cut tissue and seal the edges against bleeding. Not something you want to do to your body on a causal basis.

Our nerves cannot perceive the passage of RF electricity, so some TC users think they are not being harmed by taking TC discharges to their extremities. That is not something I would want to do.

To answer your specific question, direct current can cause involuntary contraction of muscles, and, if passed through the heart, cardiac arrest. RF will cause tissue burns and probably long term nerve damage.

Dave

On 8/18/2012 4:42 PM, Jerry Turdjmann wrote:
Hello,
I'm trying to learn the basics of High Voltage electrical safety, so,
a safety issue, and perhaps an ingenuous question :

what is the difference between a current output of 10 mA from a flyback
and a direct current (not pulsed) of the same intensity of 10 mA provided
by a low voltage power supply : I see what gives this one, but what
are the differences of the flyback in effects on the human body ?

If the intensity is the same, the power output of a flyback is higher than that
of a low voltage power supply ?
eg : 30 000 V . 0,01 A = 300 W (flyback power output)    beside     10 V . 0,01 A = 0,1 W
So, is there a difference in effects on the human body from this higher power
even with the same current ?

Any (detailed) explanation would be welcome !

Alphonse

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