22
Rockwell Automation Publication 1606-RM104A-EN-P - July 2020
Parallel Use for 1+1
Redundancy
The device can be used to build 1+1 redundant systems.
Devices 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 device fails. The simplest way is to put two devices in parallel.
This is called a 1+1 redundancy. In case one device fails, the other one is
automatically able to support the load current without any interruption. It is
essential to use a redundancy module to decouple devices from each other.
This helps prevent the defective unit from becoming a load for the other
device, and thereby helps ensure that the output voltage is maintained.
1+1 redundancy allows ambient temperatures up to 70 °C (158 °F).
Leakage current, EMI, inrush current, and harmonics increase when using
multiple devices.
Recommendations for building redundant power systems:
• Use separate input fuses for each device.
• Use separate mains systems for each device whenever it is possible.
• Monitor the individual devices. Therefore, use the DC OK signal of the
device.
• Set the output voltages of all devices to the same value (± 100 mV) or
leave it at the factory setting.
Figure 24 - 1+1 Redundant wiring with a 1606-XLSRED4HE
Figure 25 - 1+1 Redundant wiring with two 1606-XLBRED20
L
N
PE
20 A
Load
Failure
Monitor
I
Redundancy
Module
Output
Input
1
Input
2
+
+
-
-
+
-
I
Power
Supply
24V, 20 A
DC-
OK
+ +
- -
L N PE
Output
Input
o
o
Power
Supply
24V, 20 A
DC-
OK
+ +
- -
L N PE
Output
Input
o
o
L
N
PE
20 A
Load
Failure
Monitor
I
Redundancy
Module
Output
Input
1
Input
2
+
+
-
-
+
-
+
I
Power
Supply
24V, 20 A
DC-
OK
+ +
- -
L N PE
Output
Input
o
o
Power
Supply
24V, 20 A
DC-
OK
+ +
- -
L N PE
Output
Input
o
o
Redundancy
Module
Output
Input
1
Input
2
+
+
-
-
+
-
+