Re: Tom Hennessey?

[Garrett Wollman <wollman>]

<<On Sat, 15 Dec 2001 18:44:34 -0500, Eli Polonsky <elipolo@earthlink.net> said:

> All the tech department said was "that's not supposed to happen with our
> power protection circuitry"! All I could say was "well, it did..."

A lot of times people overload their UPSen.  Most ``UPS'' products on
the market today are not true Uninterruptible Power Supplies; rather,
they are Standby Power Supplies, which happen to be a good deal more
energy efficient, but depend on the equipment having enough
capacitance in the power supply to bridge the interval between the
power loss and the inverter starting.  In a true UPS, the inverter is
always running, and the protected equipment never sees an
interruption.  (At least, not until the barrety runs out.)  An SPS is
more efficient because, in normal operation, it doesn't suffer from
the AC->DC->AC conversion losses inherent in a UPS.  This also means
that it usually doesn't complain about being overloaded until the
inverter is switched on during a power failure.

A high-end backup power system, such as might be used for an important
data center, might have three stages: a battery-backed UPS, a flywheel
energy-storage system, and a diesel generator.  The UPS rides the
transients, and also smooths the (usually poor-quality) generator
output; the flywheel stores enough energy to keep things running for
the time it takes the generator to start and get up to operating
speed.

-GAWollman