User guide

A120 Power Supplies
182
890 USE 108 00 August 2001
Overload and
Overvoltage
Protection
The P120-125 has internal overvoltage protection, preventing the output voltage
from exceeding 36 V should the supply lose regulation. The P120-125 also has
internal overload protection which permits the unit to safely transition into a short
circuit for a period no greater than 5 min.
LED Indicator The P120-125 has one green LED indicating, when ON, that the unit is supplying dc
power within regulation (+5%). Marginal regulation-line voltage provided but below
the required 5% minimum-causes the LED to glow dimly. The LED goes OFF upon
loss of regulation.
Note: It is not recommended that a single P120-125 power supply be used to
power the Compact 984 and its I/O.
A separate supply, which may be a P120-125, is recommended to reduce the risk
of field noise affecting the controller’s operation. This is also beneficial in cases of
single-supply configurations, where a field point failure could cause the controller
to shut down.