Rockwell Automation Publication 440C-WD001C-EN-P - June 2015 59
Chapter 12
Dynamic Feedback
This application example shows how to configure the CR30 safety relay to
monitor the feedback contact of an output device dynamically.
With safety rated relays and contactors, the normally closed feedback contacts
are
either positively guided, mechanically linked, or mirrored. These features are
designed to help ensure that the normally closed contact moves with the normally
open contacts. If the safety rated relay or contactor were to weld or get stuck in
the closed position, the normally closed contact would remain open. If open,
then the safety system would not turn the outputs ON.
The process that is described in the previous paragraph does not detect wiring
shor
ts across the normally closed contacts, and some devices do not have
mechanically linked contacts.
The application note shows how to monitor one or more feedback contacts
dyn
amically. If any one of the feedback contacts does not open (or is shorted to
24), and the output device is energized; the CR30 safety relay turns off all output
devices.
Product Overview
Figure 39 - Overview
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