Want to move to all 208V for server racks
Ingo Flaschberger
if at xip.at
Fri Dec 3 18:23:44 UTC 2010
Dear Leo,
> I worked in a data center with something I thought was very, very cool.
>
> http://www.hilkar.com/highresistance.htm
>
> The concept, at a high level, is rather than tie the (service, not
> signal) ground back to grounding rods directly you run it through a
> large resistor. Now when a phase is "grounded" it runs through the
> resistor, allowing a small but safe current to flow.
currents above 1mA and 50V are dangerous.
also the net-frequency of 50hz/60hz cause troubles for the heart
(Ventricular fibrillation).
If a really fail-tolerant system is needed, that the only solution if to
have a ground-free system. the incomming power is transformed (1:1 for
example) and not earthed.
a special device monitors the voltage between earth and power and do an
alarm if one of the power-lines connects to earth - but do no shutdown.
the fault can then be repaired without shutdowns.
only when 2 faults occur the breakers trip.
usually hospitals use such a configuration.
probably hilkar system is similar to this one.
Kind regards,
Ingo Flaschberger
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