Specifications

RN: 5-88
RS3: Software Release Notes for P1 R4.2
Changes to RS3 Manuals
Description: Information under the heading “Finding the Number of
Power supplies Required” on page 1-2-12 was changed to read as
follows.
AC/DC Power Supplies
To determine the number of AC/DC Power Supplies needed to power
the DC bus:
1. Add the DC current requirements of all equipment that will be fed
from the DC bus.
2. Add an allowance for equipment expansion.
3. Divide the total current by 18 amps to determine the number of
power supplies required to supply the load. This is an empirical
number that will permit sufficient capacity to handle inrush
current at startup. The 18 amps may be reduced to provide extra
capacity if the user expects future expansion of the system:
Power Supplies Needed =
Total DC Load Current
18 Amps per Power Supply
4. Round up the r esulting number to the next higher whole number
to find the number of power supplies needed.
Many sites add one extra supply as an on-line standby. This provides
N+1 redundancy coverage should one supply fail.
The limit is ten AC/DC Power Supplies on one bus. One additional
power supply may be added for redundancy. The power supply is rated
for a maximum DC output of 22 amps. Normal design loads each supply
at about 10 to 18 amps. The crest factor (peak current divided by
average current) is approximately 1 .3. The power factor is about .90
lagging.
System Power Supply Units
To determine the number of System Power Supply Units needed to
power the DC bus:
1. Calculate the total DC current load.
2. Divide the DC load by 43 (43 amps is the rated output for each of
the power supply modules when they are connected on a DC
bus).
3. Round up to the next whole number.
4. Add one for r edundancy.
NOTE: If the DC bus is in a redundant bus configuration, do not
add anything for redundancy.