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Old February 9th, 2018, 01:31 PM   #6
United States

Timeismoney08 is offline
Join Date: Jul 2012
Location: United States
Posts: 251
Originally Posted by mk42 View Post
Generally, you use TWO contactors, so that if one welds shut, the other will still break the circuit. You should also be using contactors with an auxiliary feedback contact, to report status back to the system/safety relay.

I believe it is usually required to have a periodic test carried out (once a shift, once a day, once a week, depending), to check for hidden faults. This is often procedural, not automated.

How do you monitor the two contactors in series with a safety relay if they only pull in when it's in a safe condition? Would I need 1 Safety relay for the E-stops and 1 for the Motor/Contactor Circuit? Could I use Auto reset on that safety relay just for the contactors?
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