User`s manual

MPS Doc: UPS_AS_UM Rev (-) May 23, 2012 Page 28 of 38
Holdup Time Vs Power” plot).
5.3.1.2. In order to allow for the 2 minutes that the operator will need to save
their work, we will need additional charge of:
100% x (2/10) = 20%.
So the “Low Charge Shutdown Threshold” will be set to 75% (95% from
5.3.1.1 less the above 20%).
5.3.2. Calculating the Required Battery Thresholds for PC-A
5.3.2.1. Since it takes PC-A 3 minutes to shutdown (and assuming that 10
seconds delay between reaching its “Low Charge Shutdown Threshold” to
the actual initiation of the Shutdown Procedure will be sufficient), the
charge that PC-A will consume from the time when its “Low Charge
Shutdown Threshold” is reached, until it is off will be:
100% x (3.15/17) = 18.5% =>20%.
When “3.15” is the 3 minutes and 10 second operation of PC-A, “17” is the
100% holdup time for 1,000W (from the “M359-1 Holdup Time Vs Power”
plot).
In order to leave 25% charge as a safety margin, the “Low Charge
Shutdown Threshold” of PC-A should be at least 45% (25% + 20%).
Since we want PC-A to operate uninterrupted for the longest possible
time (but still ensure safe shutdown), we will set the “Low Charge
Shutdown Threshold” of PC-A to the minimum safe value that we have
calculated (45%). No early warning is required for PC-A, so we will set it to
the same level as the “Low Charge Shutdown Threshold”.