Rockwell Automation Publication ICSTT-RM447M-EN-P - July 2019 107
Specifying a New Controller Chapter 6
System Power Requirements
A controller's system power should be supplied from two different 24 Vdc
(Nominal) power supplies with a common return path; that is, the 0 V return
will be the same between the power feeds. Each controller also requires an
external field power source for the field loops.
This means that a controller must be supplied with system power from a power
source that complies with SELV and PELV standards.
• SELV (safety extra-low voltage) is a voltage which is no larger than 30
Vrms, 42.4 Vpeak and 60 Vdc between conductors, or between each
conductor and earth in a circuit which is isolated from the line voltage
by a safety transformer.
• PELV (protected extra-low voltage) is an extra low voltage circuit with a
protective partition from other circuits which has a protective earth
connection.
To satisfy SELV and PELV requirements the power source must have a safety
transformer with a protective partition between the primary and secondary
windings so that the windings are galvanic and electrically isolated.
Power Arrangements for Field Devices
Output modules use an external source of power for field devices. This may be
the power source used for the controller or a separate power source.
9451 18-32 165 Output: 18-32 Vdc @ 0.5 A, Pilot duty
16 VA, 1.5 A Inrush
9801 18-32 6.5 -
9802 18-32 6.5 -
9803 18-32 6.5 -
9831 18-32 0-24 -
9832 18-32 0-24 -
9833 18-32 0-24 -
9851 18-32 500 -
9852 18-32 500 -
9892 18-32 500
9881 18-32 0-24 -
9882 18-32 0-24 -
Module Back-plane Electrical Ratings Input/Output Electrical Ratings
Voltage Range (Vdc) Maximum Current (mA)
WARNING: A controller system must be installed with a power network that
is designed to meet over voltage Category II
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