User guide

A120 Power Supplies
890 USE 108 00 August 2001 179
The P120 module is designed to be inserted in any available I/O slot in the DTA 200
backplane just like a standard A120 I/O module, but it does not make any
connections to the backplane. No jumper changes or switch setting changes are
required when changing from 115 Vac to 230 Vac power input, or when changing
from 230 Vac to 115 Vac input.
Overload and
Overvoltage
Protection
The P120 has internal overvoltage protection, preventing the output voltage from
exceeding 35 V should the supply lose regulation. If an overvoltage condition is
sensed, the P120 shuts down and will not restart until the ac input power source has
been turned OFF for a minimum of 5 min. The P120 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 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 power supply be used to power
the Compact 984 and its I/O.
A separate supply, which may be a P120, 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