Rockwell Automation 1768-PA3_PB3 CompactLogix Power Supplies Installation Instructions - Manual (Page 12)

12 1768 CompactLogix Power Supplies
Publication 1768-IN001B-EN-P - July 2006
Main Power Disconnect
Place the main power disconnect switch where operators and maintenance
personnel have quick and easy access to it. In addition to disconnecting electrical
power, de-energize all other sources of power (pneumatic and hydraulic) before
working on a machine or process controlled by a controller.
Isolation Transformers
We recommend that you use an isolation transformer in the ac line. This type of
transformer provides isolation from your power distribution system to reduce
electrical noise and is often used as a step-down transformer to reduce line voltage.
Any transformer used with the Compact I/O system must have a sufficient power
rating for its load. The power rating is expressed in volt-amperes (VA).
Power Supply Inrush
During power-up, the power supply allows a brief inrush current to charge internal
capacitors. Many power lines and control transformers can supply inrush current
for a brief time. If the power source cannot supply this inrush current, the source
voltage may sag momentarily.
The only effect of limited inrush current and voltage sag on the system is that the
power supply capacitors charge more slowly. However, the effect of a voltage sag
on other equipment should be considered. For example, a deep voltage sag may
reset a computer connected to the same power source.
WARNING
Explosion Hazard - Do not replace components or disconnect equipment
unless power has been switched off.