Rockwell Automation Publication 1769-IN028C-EN-P - August 2016 7
Compact I/O Expansion Power Supplies
About the Power Supplies
Compact I/O™ power supplies provide 120/240V AC and 24V DC power to modules, which
you can place to the left or the right side of the 1769 power supply. As many as eight I/O
modules can be placed on each side of the power supply.
Before You Begin
There are some points about power distribution that you must know.
• The master control relay must be able to inhibit all machine motion by removing power
to the machine I/O devices when the relay is de-energized. We recommend that the
controller remains powered even when the master control relay is de-energized.
• If you are using a DC power supply, interrupt the load side rather than the AC line
power. This operation avoids the additional delay of power supply turn-off. The DC
power supply must be powered directly from the fused secondary of the transformer.
Power to the DC input and output circuits must be connected through a set of master
control relay contacts.
Perform Periodic Tests of Master Control Relay Circuit
Any part can fail, including the switches in a master control relay circuit. The failure of one of
these switches would most likely cause an open circuit, which would be a safe power-off failure.
However, if one of these switches shorts out, it no longer provides any safety protection. These
switches must be tested periodically to make sure they stop machine motion when needed.
ATTENTION: This equipment is not resistant to sunlight or other sources of UV radiation.
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