User`s manual

MPS Doc: UPS_AS_UM Rev (-) May 23, 2012 Page 27 of 38
5.3. A Two PC System
There may be a situation when a number of PC stations are supported by a single
UPS. Moreover it may be required to shut down some none-critical stations (in
order to save battery energy) while allowing the critical one to keep operating.
For example let's consider two stations: PC-A and PC-B, supported by single M359-1
UPS. PC-A in our example is a critical server that consumes 1,000W (including all its
peripherals) and takes 3 minutes to safely shutdown. We are required to maximize
its “ride-through” time (the longest duration of AC Main power failure that it can
tolerates without interruption).
PC-B in our example is a non-critical 500W PC that we want to run uninterrupted
during short fluctuations (shorter than 30 seconds) of the AC Main power, but we
can tolerate its shutdown during long power failures. PC-B of this example takes 2
minutes to shut down and its operator will need an advanced 2 minute warning to
save their work.
5.3.1. Calculating the Required Battery Thresholds for PC-B
5.3.1.1. In order to allow 30 seconds of uninterrupted operation of PC-B, its
“Low Charge Warning Threshold” needs to be:
100% - 100% x(0.5/10) = 95%
When “0.5” is the 30 seconds uninterrupted operating time of PC-A when
both PC-A and PC-B are operating and consuming 1,500W. The “10” is the
10 minutes that 100% charge can support 1,500W (from the “M359-1
UPS
Power Line
PC B
LAN
PC A