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Don Klipstein
Guest
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 Posted:
Wed Jun 01, 2005 4:52 am Post subject:
Re: electrocution by car battery |
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What I expect:
15 mA has minimal (but not zero) electrocution risk, although by many
(but not all) accounts is able to cause humans to latch onto shocking
conductors, and become unable to let go and may die from fibrillation
resulting from prolonged shock or may die from breathing muscles being
impaired by the shock.
Main result that I expect from 113 watts of power dissipation into a
human body is burns.
With initial contact resistance of 500K ohms (highish side but fairly
typical of human contact with wires), I expect most of this resistance tio
be in small volumes of skin, that get burned through quickly with 113
watts. That means the victim of such a neon sign transformer shock
quickly gets to dissipate a small fraction of the above-mentioned 113
watts, while conducting a current close to 30 mA - which has a non-zero
chance of being fatal.
Another thing: The output impedance of neon sign transformers is mostly
inductive reactance rather than resistance. Put a 500K-ohm load across
the output of a 15KV 30mA neon sign transformer, and you get more than
7.5 KV at 15 mA, as in closer to 10 KV at 20 mA, ideally 10.3 KV at 20.6
mA.
- Don Klipstein (don@misty.com)
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Don Klipstein
Guest
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| Posted:
Wed Jun 01, 2005 4:57 am Post subject:
Re: electrocution by car battery |
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This is much less current than I have found from a few neon sign
transformers and "oil burner" transformers. In my experience, the
short-circuit current using the entire secondary is close to the "label"
current or slightly higher, and with a load whose impedance is the ratio
of rated voltage to rated current I find voltage and current typically
around 60-66% of the "label" values.
- Don Klipstein (don@misty.com) |
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DaveC
Guest
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| Posted:
Wed Jun 01, 2005 6:42 am Post subject:
Re: electrocution by car battery |
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| Quote: | I'm not reading a news source, just stating experience.
I've been shocked many times from line voltages with
no ill effects. Once, I was shocked by 10KV from
an aviation radar system, and it threw me across the room,
but I got up and went back to work.
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Your experience notwithstanding, people die from 110 vac. You're healthy and
lucky. Not everybody is.
--
Please, no "Go Google this" replies. I wouldn't
ask a question here if I hadn't done that already.
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
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Don Klipstein
Guest
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| Posted:
Wed Jun 01, 2005 1:53 pm Post subject:
Re: electrocution by car battery |
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The data posted shows 78.8% of short-circuit current with a load that
loads down the output voltage to half the open circuit voltage.
Ideally, inductive reactance such as leakage reactance would result in
86.6% of short circuit current to a load that loads down the output
voltage to half the open circuit voltage.
I believe the data above show resistance being part of the output
impedance, and/or the leakage inductance being nonlinear (less at higher
current).
One thing I have experienced: Output impedance (ratio of open circuit
voltage to short circuit current at least) of an oil burner transformer
being higher when the input voltage is decreased.
- Don Klipstein (don@misty.com) |
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Guest
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| Posted:
Wed Jun 01, 2005 4:35 pm Post subject:
Re: electrocution by car battery |
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John Fields wrote:
| Quote: | On Mon, 30 May 2005 18:39:58 -0400, John Popelish <jpopelish@rica.net
wrote:
It can't, since it's designed to saturate at 30mA, but looking at its
load line it'll put out, say, 15kV at 0A into an open, and 0V at 30mA
into a dead short.
That means that with an initial 500kohm human load across it its
output voltage will drop to 7500VRMS and it'll be forcing 15mA through
the load, and the load will be dissipating about 113 watts. OUCH!!!
You may be right, but that is not what I understand to be the case. I
thought they are rated for normal load current over the voltage range
expected when driving a gas tube. And that they have a very nonlinear
current limit, much like Sola ferro resonant constant voltage
transformers. Those hold specified voltage regulation at rated
current but the current increases only to about double rated under a
short circuit. I don't think most neon sign transformers are just a
tightly coupled step up transformer in series with a big resistor.
---
AIUI, they're designed to be ballasts. That is, to start off with a
high enough voltage to strike the arc through the tube and then to
provide the proper current (30 or 60 mA) to run the tube when the gas
ionizes and provides a more or less constant low-resistance load
through the plasma.
Using a Transco T1512, which is a 15kV 30mA NST, like this:
Iout-
120VAC>----+ +---------+ <-----+
)||( | |
)|| >-GND [R] Eout
)||( | |
120VAC>----+ +---------+ <-----+
I get the following data:
R Eout Iout
M kV pk mA RMS
-----+-------+--------
0.00 0.000 17.3
0.05 0.662 17.3
0.09 1.647 17.1
0.13 2.586 16.8
0.17 3.456 16.3
0.21 4.270 15.9
0.25 5.02 15.5
0.29 5.744 15.1
0.33 6.37 14.7
0.37 6.971 14.3
0.41 7.511 13.8
2.0 10.0 6.6
4.0 10.8 5.5
5.0 11.0 5.3
10.0 11.37 5.2
20.0 11.55 5.1
INF 15.0 0.0
Which shows there's no voltage regulation at all, but only a 3.5mA
change in current for a 7500V change in voltage across the load from
410kohms to a dead short.
The reason the short-circuit current is 17.3 mA instead of 30 is
because I loaded the entire secondary, and it's wired so you can only
get 15mA or so that way. If you take current from either end of the
secondary to the center tap you can get 15mA out of each half of the
secondary for a total of about 30mA.
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Facts are so much better than assumptions. Thanks for going to this
trouble for all of us. I dug a bit deeper, and my assumptions fell
through. I was thinking of the effect of the resonant circuit in a
ferroresonant transformer, and apparently, neon sign transformers have
only leakage inductance (more like the character of a microwave oven
transformer or welder), which would agree well with your measurements.
But I wonder how they get it to act as nonlinear as it does. It seems
strange that the short circuit current is only about 1.25 times as high
as the current that pulls the output voltage down by half. That surely
looks like an attempt at current regulation. On a graph of this data,
there is a bit of a kink. |
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John Fields
Guest
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| Posted:
Wed Jun 01, 2005 9:34 pm Post subject:
Re: electrocution by car battery |
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| Quote: | Facts are so much better than assumptions. Thanks for going to this
trouble for all of us. I dug a bit deeper, and my assumptions fell
through. I was thinking of the effect of the resonant circuit in a
ferroresonant transformer, and apparently, neon sign transformers have
only leakage inductance (more like the character of a microwave oven
transformer or welder), which would agree well with your measurements.
But I wonder how they get it to act as nonlinear as it does. It seems
strange that the short circuit current is only about 1.25 times as high
as the current that pulls the output voltage down by half. That surely
looks like an attempt at current regulation. On a graph of this data,
there is a bit of a kink.
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---
Yes, at the high voltage end I used a bunch of 20 megohm metal oxide
resistors for the load, but I'm pretty sure they aren't rated for
10-15kV, so that may be where the kink came from. Or, measurement
error :-(
There's another problem I'm trying to solve, though, and that's why
the output current is so low. I had thought that 15mA out of each
secondary to the center tap would result in 30mA total, but that's not
right. I called the manufacturer and their tech guy said that I ought
to get 30mA RMS out of the entire shorted secondary, just like Don
said. Well, he didn't say RMS, but...
The strange part is I've got a 9kV and a 15kV transformer, and I get
the same short circuit current out of both of them, making several
measurements with different meters.
I've got a friend who owns a sign shop, so I guess the next thing I'll
do is take a meter over there and see what a known good transformer
puts out.
--
John Fields
Professional Circuit Designer |
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Guest
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| Posted:
Thu Jun 02, 2005 7:27 am Post subject:
Re: electrocution by car battery |
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John Fields wrote:
(snip)
| Quote: | There's another problem I'm trying to solve, though, and that's why
the output current is so low. I had thought that 15mA out of each
secondary to the center tap would result in 30mA total, but that's not
right. I called the manufacturer and their tech guy said that I ought
to get 30mA RMS out of the entire shorted secondary, just like Don
said. Well, he didn't say RMS, but...
The strange part is I've got a 9kV and a 15kV transformer, and I get
the same short circuit current out of both of them, making several
measurements with different meters.
I've got a friend who owns a sign shop, so I guess the next thing I'll
do is take a meter over there and see what a known good transformer
puts out.
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Excellent. I love experimental science.
--
John Popelish |
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Bill Bowden
Guest
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| Posted:
Sun Jun 05, 2005 8:35 am Post subject:
Re: electrocution by car battery |
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| Quote: | Your experience notwithstanding, people die from 110 vac.
You're healthy and lucky. Not everybody is.
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Actually, I'm not healthy, but I am lucky. I have coranary heart
disease and luckily had a triple bypass operation last year that
brought me back to normal. I had angina pains when walking uphill, so I
went to a cardiologist, who gave me a treadmill test, and then told me
to go to the hospital. I was lucky again to have insurance that paid
$85,000 for the angiogram and surgery. Otherwise, I would be bankrupt
today.
But I feel pretty good now. I can walk uphill for long distances and
climb 4 flights of stairs with no pain.
Haven't tried the 120VAC shock test yet, but I'm really more afraid of
falling down than getting shocked.
Last month, I fell down and hit my head on a open tool box and needed 5
stitches. I would have much prefered being shocked from 120VAC than
smashing my head on a open tool box.
-Bill |
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Gilbert
Guest
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| Posted:
Mon Jun 06, 2005 12:35 am Post subject:
Re: electrocution by car battery |
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When I was a kid my older brother had an "Electric Lab", the lab
contained a device that was a coil with contacts. The Idea was to
connect a small battery 1.5v to it and adjust the contacts to
"resonate" ( switch on/of continuosly ) . It had also 2 wires ending
in 2 separate pieces of pipe that I will hold and feel the
electricity.
I was used to connect it to an old train toy AC adapter and set it up
full blast.
I had to grab the pipes carefully ( more than letting them rest in the
palms of my hands and slowly grab them. I could feel the electricity
moving all the muscles of my hands and arms. So much that sometimes it
was difficult to open my hands to let go.
I also played with a neon sign transformer that make an arch 2 inches
long , and thru wood. When I turned off the light to do it I coud see
the cable and my fingers with a light blue color, I think it was 15000
volts. I got a shock once with it but the electricity whent in and out
in my hand , so nothing happened to me.
At school there was a cold water fountain that will shock you if you
touched it at the same time that the surrounding wall. I used to be in
line to drink water and touch the wall and the ears of the one
drinking water..... |
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drake89
Joined: 02 Apr 2006
Posts: 1
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| Posted:
Sun Apr 02, 2006 8:16 pm Post subject:
neon sign shock |
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| im going to build a tesla coil and just bought a neon sign transformer. 7500V 0.30mA. i was playing with it (making cool arcs) and i just got zapped. it scared me because i heard you can die from it (i had one wire in each hand so i suppose it went across the heard). the funny thing is that i was holding onto the thick insulation and several inches from the exposed ends. any ideas on how the hell i got shocked. i now respect electricity. |
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neon
Joined: 25 Feb 2006
Posts: 580
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Mon Apr 03, 2006 7:24 am Post subject:
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| why 12 volts as pointed out allready is not the voltage that kill you but rather the current. so now the question arise what can kill you well a 1.5 volt cell can supply enough power to kill you. all timers tested battery by licking one terminal with the toungue to see if it tingle yes it does. DON'T TRY THAT it can and did kill. normaly a healthy person can begin to feell around 28v using the skin to limit the current. now lets supply a small cut to the blood source which is mostly sodium {metal} and current increases dramatically killing you by basicaly stopping the heart. and an item of interest is that most accidental electricusion the terminal of exit mostly is the private part between your legs because of vast blood supply. |
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neon
Joined: 25 Feb 2006
Posts: 580
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| Posted:
Fri May 05, 2006 5:39 pm Post subject:
Re: electrocution by car battery |
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| Anonymous wrote: | what i meant was after stepping up the battery to a very high voltage
such as 110 or 240 volt... would it kill you if you touch the terminal
at the point after stepping it up? cuz from my guess it should right?
because the voltage is now high enough to penetrate the skin and the
current is also quite big. |
voltage does not kill you currebt does I GOT BITTEN BY 25KV TV many times but with 10mega in series all i got is mad at it and me. |
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neon
Joined: 25 Feb 2006
Posts: 580
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Fri May 05, 2006 5:56 pm Post subject:
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| I read and read but the fact still remain that is not the voltage that kill but the current thru your heart that stop that machine to operate properly. so a D cell 1.25v is that good enough to kill you absolutelly. The D cell can provide 2 amps into a short circuit for quite some time the voltage will probably say zero but the current will be there to kill you. Now before i get some wise guy to tell me BS here is the way break the skin and do it instant death blood is rich with sodium [metal] that will conduct very well the current neccessary to kill. anybody got hit by 25kv TV i did countless of times and from cars system too no damage because of skin resistance and thank to for the 10 megohms in series. so finaly and in conclusion the current is the killer not the volts. |
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neon
Joined: 25 Feb 2006
Posts: 580
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Sat May 20, 2006 6:02 pm Post subject:
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| The fact is a 1.5 vplain D cell can and will kill you. they are capable to supply ~2 amps I will not guess but 2 amps thru your hart will defenetly do you no good. It is not the potential that kill it is ruther the current how? it depends on too many factors to enumerate. A D cell can provide ~2amps into a short. now before some smart aleck claim BS the trick is to pass the current thru the heart. just plain skin resistance will stop the flow. but break the skin and the flow into sodium rich blood?. well don't try to prove me wrong. |
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