Hardware reference guide

Pwr. & Grnding. Guide
744
35013379 11/2011
Similar to the summable supplies, the Quantum redundant power supplies also
contain circuitry which forces the installed power supplies to share output current
almost equally. An important difference between the summable and the redundant
supply lies in the system POK generation circuitry.
The Quantum system POK signal in systems powered by redundant power supplies
is true (power is OK) if either or both internal POK is true. The following figure shows
the internal Quantum redundant supply POKs are ORed to create the Quantum
System POK.
NOTE: Redundant power supply module health may be monitored in an I/O module
health status word. (Refer to the STAT Block description in Modicon Ladder Logic
Block Library User Guide, 840USE10100.)
Another important difference from the summable system is the total available
system backplane loading. If there are N redundant power supplies installed in a
backplane, the total backplane load must not exceed the capability of N – 1 supplies.
For example:
z If three 8 A redundant power supplies are installed (N = 3), the maximum
backplane load available for redundant operation is the current sourced by N – 1
( = 2) supplies, which is 16 A.
z if two 8 A power supplies are installed in the backplane (N = 2), the maximum
backplane load available for redundant operation is the current sourced by N – 1
( = 1) supplies, which is 8 A.