Rockwell Automation 1768-PA3_PB3 CompactLogix Power Supplies Installation Instructions - Manual (Page 7)

1768 CompactLogix Power Supplies 7
Publication 1768-IN001B-EN-P - July 2006
The controller converts the 24V dc to 5V dc and distributes 5V dc and 24V dc
power as required by modules on the backplane. The following list describes
controller power distribution considerations:
• 5V/24V power goes to 1769 I/O modules on the right side of the controller.
• 5V power goes to 1768 communication or motion modules on the left side
of the controller.
• System power-up and power-down may take longer than expected.
• Full power-up should occur within a few seconds of turning on the power
supply. Power-down, however, takes significantly longer. When the power
supply is turned off, the CompactLogix controller uses some power to write
its program to internal memory. During this program write, there is activity
on the controller’s status indicators.
• If your system is not receiving power, the cause may or may not be the
power supply.
For example, if a 5V short exists in the 1769 I/O portion of the local chassis,
the controller faults and stops powering the 1769 I/O until the short
condition is corrected. In this case, the power supply is operating normally
and continuing to send 24V dc to the controller.
To troubleshoot any power supply issues, see Interpret the LED Indicators.
• 1769 CompactLogix I/O modules in the local chassis receive power from the
1768 power supply. However, banks of 1769 I/O modules remote to the
1768 power supply require that a 1769 power supply be installed in the
remote bank.
IMPORTANT
When you turn the CompactLogix power supply off, make sure you wait for all
status indicators on the power supply and controller to turn off before
disconnecting any part from the system.
If you disconnect the CompactLogix system while the controller is still writing
its program to memory, the program write will not be completed and you will
lose your program.
IMPORTANT
Never install a 1769 power supply on the local 1768 CompactLogix
backplane.