Rockwell Automation 1606-XLE96B-2 Power Supply Reference Manual - Manual (Page 19)

All parameters are specified at 12V, 2.5A,230Vac input, 25ªC ambient and after a 5 minutes run-in time, unless noted otherwise.
Rockwell Automation Publication 1606-RM030A-EN-P — April 2014 19
Bulletin 1606 Switched Mode Power Supplies
22.6. Parallel Use to Increase Output Power
1606-XLE96B-2 power supplies can be paralleled to increase the output power.
This power supply does not include the capacity to balance the load current
between the power supplies. Usually the power supply with the higher
adjusted output voltage draws current until it goes into current limitation.
Therefore, the power supply can only be used in parallel as long as the
ambient temperature stays below 45°C. The output voltages of all power
supplies shall be adjusted to the same value (±100mV). A fuse or diode on
the output of each unit is required only if you connect more than three units
in parallel. If using a fuse or circuit breaker, choose one with approximately
150% of the rated output current of one power supply. Maintain an
installation clearance of 15mm (left / right) between two power supplies and avoid installing the power supplies on
top of each other. Do not use power supplies in parallel in mounting orientations other than the standard mounting
orientation (input terminals on the bottom and output terminals on top of the unit) or in any other condition where a
derating of the output current is required (e.g. altitude, above 60°C, …). Please note that leakage current, EMI,
inrush current and harmonics will increase when using multiple power supplies.
Unit A
AC
DC
Unit B
AC
DC
-
+
-
+
Load
+
-
22.7. Parallel Use for Redundancy
Power supplies can be paralleled for redundancy to gain higher system availability. Redundant systems require a
certain amount of extra power to support the load in case one power supply unit fails. The simplest way is to put two
power supplies in parallel. This is called a 1+1 redundancy. In case one power supply unit fails, the other one is
automatically able to support the load current without any interruption. Redundant systems for a higher power
demand are usually built in a N+1 method. E.g. six power supplies, each rated for 8A are paralleled to build a 40A
redundant system. For N+1 redundancy the same restrictions apply as for increasing the output power, see also section
22.6.
Please note: This simple way to build a redundant system does not cover failures such as an internal short circuit in
the secondary side of the power supply. In such a case, the defect unit becomes a load for the other power supplies
and the output voltage can not be maintained any more. This can only be avoided by using decoupling diodes
which are included in the 1606-XLSRED decoupling module.
Recommendations for building redundant power systems:
a)
Use separate input fuses for each power supply.
b) Monitor the individual power supply units.
c) 1+1 Redundancy is allowed up to an ambient temperature of 60°C
N+1 Redundancy is allowed up to an ambient temperature of 45°C
d) It is desirable to set the output voltages of all units to the same value (± 100mV) or leave it at the factory setting.