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Bulletin 1606 Switched Mode Power Supplies
23.7. Parallel Use to Increase Output Power
Power supplies from the same series (XLS) can be paralleled to increase
the output power. The output voltage shall be adjusted to the same value
(±100mV) with the same load conditions on all units, or the units can be left
with the factory settings.
If more than three units are connected in parallel, a fuse or circuit breaker
with a rating of 6A or 10A is requird on each output. Alternatively, a diode
or redundancy module can also be used.
Keep 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 bottom and output terminals on the top of the unit) or in any other condition where a derating of the output
current is required (e.g. altitude, above 60°C, ...).
Pay attention that leakage current, EMI, inrush current, harmonics will increase when using multiple power supplies.
23.8. 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. five power supplies, each rated for 5A are paralleled
to build a 20A redundant system. For N+1 redundancy the same
restrictions apply as for increasing the output power, see also
section 23.7.
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 defective unit becomes a
load for the other power supplies and the output voltage can not
be maintained any more. This can be avoided by using decoupling
diodes which are included in the 1606-XLSRED redundancy module.
Recommendations for building redundant power systems:
a)
Use separate input fuses for each power supply.
b)
Monitor the individual power supply units. Therefore, use the DC-OK relay contact of the 16060-XLS power supply.
c)
It is desirable to set the output voltages of all units to the same value (± 100mV) or leave it at the factory setting.
All parameters are specified at 48V, 5A, 230Vac, 25°C ambient and after a 5 minutes run-in time, unless noted otherwise.
24
Rockwell Automation Publication 1606-RM045A-EN-P — March 2014
Unit A
AC
DC
Unit B
AC
DC
- -
-
-
+ +
+
+
IN 1
IN 2
48V,5A
Adj
DCok
Overload
1606-
1606-
1606-
XLSRED
XLS240F
XLS240F
Redundancy
Module
Power
Power
Supply
Supply
OUT
L N PE
-
+
optional
I
L
N
PE
+
-
+
Load
+
-
-
Failure
Monitor
- -
+ +
48V, 5A
Adj
DCok
Overload
L N PE
I
24V,10A
Load
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