ABB RELION REX640 Technical Manual page 112

Basic functions
TO
IRF
<U
TC1
DCS
F1
In example 2, the fail-safe approach aims at securing motor shutdown via an
emergency switch and in case the control voltage disappears. In case of internal
relay fault, the necessary actions must be initiated by the process operators or by
the control system.
-F1
Figure 33: Motor feeder fail-safe trip circuit principle, example 3
A1
ES
Q0
TO
IRF
<U
TC1
K1
F1
In example 3, the fail-safe approach aims at securing motor shutdown via an
emergency switch and in case the control voltage disappears. In case of internal
relay fault, the circuit breaker is tripped via an undervoltage coil after a preset time
delay. The additional time delay allows the relay to recover from the internal fault
situation without tripping the circuit breaker.
112
Protection relay trip output
Internal relay fault indication
CB undervoltage trip coil
CB trip coil 1
Distributed process control system
Miniature circuit breaker
Control +
-K1
-A1
ES
TO
-Q0
<U
TC1
Control -
Protection relay
Emergency stop
Circuit breaker (CB)
Protection relay trip output
Internal relay fault indication
CB undervoltage trip coil
CB trip coil 1
OFF delay time relay
Miniature circuit breaker
AUX. POWER
IRF
-K1
1MRS759142 F
REX640
Technical Manual