In message
<201048ea81ba0745aca78e4cc8839001c8b...@desmdswms201.des.grplnk.net>,
dated Mon, 13 Aug 2007, "Haynes, Tim (SELEX) (UK Capability Green)"
<tim.hay...@selex-sas.com> writes:
>BS EN 50191 (erection and operation of electrical test equipment) has
>the following definition of "safe" electrical energy...
>
>For frequencies below 500Hz...
>
>25Va.c. or 50Vd.c. AND is SELV or PELV
>If the voltage exceeds that above, it is still a safe voltage if the
>current through a non-inductive resistor does not exceed 3mA a.c. or
>12mA d.c.
>
>And the discharge energy does not exceed 350mJ up to 1000V
>
>Elsewhere I have seen 45uC listed as the maximum charge on high voltage
>that would be considered safe. I don't have the reference to hand but I
>am looking for it.
The only one of those that is 'energy' is the 350 mJ. In any case, the
values are surprising, and not related to values in other safety
standards. For example, before IEC 60990 (on touch current measurement)
was written, IEC 60065 5th edition listed maximum permissible values for
consumer electronic products, but these are related much more to 'does
not create an unpleasant sensation', rather than 'does not threaten
life':
Antenna and (functional) earth terminals: 0.7 mA peak AC, 2 mA DC
through 2000 ohms;
Antenna terminal: maximum stored charge 4.5 μC;
Other parts: 0.7 mA peak AC, 2 mA DC through 50 kohms,
and:
- between 34 V peak and 450 V peak, maximum capacitance 1 μF;
- between 450 V peak and 15 kV peak, maximum charge 45 μC;
- above 15 kV peak, maximum energy 350 mJ
--
OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk
There are benefits from being irrational - just ask the square root of 2.
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
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