Trip Circuit Supervision With Two Digital Inputs - Allen-Bradley Rockwell Automation 857 User Manual

Trip Circuit Supervision with Two Digital Inputs

The first digital input is connected parallel with the trip contacts
(Figure 8.8).
The second digital input is connected parallel with the auxiliary
contact of the circuit breaker.
Both inputs are configured as normal closed (NC).
The digital input delay is configured longer than maximum fault
time to inhibit any superfluous trip circuit fault alarm when the
trip contact is closed.
The trip relay should be configured as non-latched. Otherwise, a
superfluous trip circuit fault alarm will follow after the trip
contact operates, and the relay remains closed because of
latching.
Both digital inputs must have their own common potential.
Digitalinputs
Trip relay
Alarm relay
for trip
circuit failure
&
close control
CB
Figure 8.8 – Trip Circuit Supervision with Two Digital Inputs
Applications
+V
AUX
tri p c ircuit
failure alar m
relay compartment
circui t breakercompartmen
-V
AUX
OPEN COIL
-V
AUX
CLOSE COIL
857-UM001A-EN-P – July 2009
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