Re: Electrocution by 3 phase

[Keith Doxey <keith.doxey@xxxxxxx>]

From: 	Harrison, Mark (Alliance)[SMTP:Mark.Harrison@xxxxxxx]
Sent: 	05 March 1999 16:51
To: 	ukha_d@xxxxxxx
Subject: 	[ukha_d] Re: x10 over three phase

> assuming you survive.

Very unlikely, I'm afraid.

As I understand things, the reason people tend to surive normal 230v AC
shocks is that every 100th of a second, the PD between the bit of their
body connected to the mains drops to zero volts relative to the bit
touching the earth. At these points (or close to them) it's _relatively_
easy to shake free of the "spark radius" and stop the current
flowing
through you.

The problem with touching two different phases of three phase is
two-fold.

Firstly, there is an AC voltage peaking at about 400v between the
phases.

Secondly, it's likely that part of you will also be grounded at the time
- this means that part of your body will always have a voltage of at
least 100ish volts - as one phase gets to zero, the next has take off.

Reason number 3.....

In order to come into contact with 2 phases normally requires that
one hand is touching one phase and the other is in contact with the
second phase. This means that the current flows ACROSS the
chest and via the heart. As Mark has previously mentioned, one of
the phases will always be at least 100 volts and even if you werent
in contact with ground, the phase that had dropped to 0V would act
as a ground. The net result is that your body has a varying voltage
of between 100 and 400 volts across it. The current would never fall
to zero and the heard would go into muscle spasm leading to death.
That is the main reason that 3 phase shocks more often than not
prove to be fatal.

Now that would not be a good start to the day :-((

To quote from "Hill Street Blues".....

LETS BE CAREFUL OUT THERE !!

Keith

Keith Doxey
http://www.btinternet.com/~krazy.keith
Krazy Keith's World of DIY HomeAutomation



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