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Trip Circuit Supervision with One Digital Input
•
The digital input is connected parallel with the trip contacts
(Figure 8.6).
•
The digital input is 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.
Digital input
Trip relay
Alarm relay
for trip
circuit failure
close control
CB
Figure 8.6 – Trip Circuit Supervision when the Circuit-Breaker is Closed
Applications
+V
AUX
trip c ircui t
failure alar m
relay compartment
circuit breaker compartment
R1
Note: The supervised circuitry in
-V
this CB position is double-lined. The
AUX
digital input is in active state. For the
OPEN COIL
application to work when the circuit-
breaker is opened, a resistor R1
must be placed. The value for it can
-V
be calculated from the external
AUX
CLOSE COIL
wetting supply, so that the current
over R1 is >1 mA.
857-UM001A-EN-P – July 2009
8-5
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