Rockwell Automation Publication 1606-RM109A-EN-P - August 2020
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Power Supply —12V, 10 A, 120 W, Single Phase
Parallel Use to Increase Output
Power
Devices can be paralleled to
increase the output power. The
output voltage shall be adjusted to
the same value (±100 mV) with the
same load conditions on all
devices, or the devices can be left
with the factory settings.
The ambient temperature is not allowed to exceed 40 °C (104 °F)
If more than three devices are connected in parallel, a fuse or circuit breaker
with a rating of 15 A or 16 A is required on each output. Alternatively, a diode or
redundancy module can also be utilized.
Energize all devices at the same time. It also might be necessary to cycle the
input power (turn-off for at least five seconds), if the output was in overload or
short circuits and the required output current is higher than the current of one
unit.
Keep an installation clearance of 15 mm (left/right) between two devices and
avoid installing devices on top of each other. Do not use devices in parallel in
mounting orientations other than the standard mounting orientation or in
any other condition where a reduction of the output current is required ( for
example, altitude). Leakage current, EMI, inrush current will increase when
using multiple devices.
Parallel Use for Redundancy
1+1 Redundancy
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 prevents an event in which that the defective unit becomes a load for the
other device and the output voltage cannot be maintained.
1+1 redundancy allows ambient temperatures up to 70°C (158 °F).
Pay attention that leakage current, EMI, inrush current, and harmonics will
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.
•
It is desirable to set the output voltages of all devices to the same value
(± 100 mV) or leave it at the factory setting.
