What you describe is one way to achieve functional safety, but many modern drives now have functional safety built in so that power does not have to be removed using a relay. This allows for faster restart after a stop as the control electronics in the drive remains powers. Also this allows the drive to incorporate more advanced stopping and monitoring safety functions for the axis.
John Figie On Mon, Aug 9, 2021, 11:49 AM Nicklas SB Karlsson <[email protected]> wrote: > Reading about emergency stop relays/contactors use to have an extra > normally closed contactor. If I got right this contactor may be used to > monitor relay is not welded together and to fulfill highest requirements > they should be monitored individually since otherwise a single failure > may be missed. Idea must be failure is very unlikely to happen exactly > then emergency stop is needed. > > > Thinking a little about it normal stop is a common operation and have > slightly different requirements if machines is enclosed with an > electrical operated lock. Stop is the same, use safety relay to > disconnect supply voltage operating the relays and other power supply > voltages which may be used to move machine parts. Then idea is to use > extra normally closed contactor to open door lock. This circuit should > be rather simple and if I think correct very safe provided > relays/contactors are built so that extra normally closed connector > never will switch on if main contactor(s) are welded together or other > failure. > > > There may of course be a problem with problem with internally stored > energy in for example DC bus capacitors. Nice thing is normal > relays/contactors may be used even though they mail fail, would even > dare to use bi-stable but it is very important normally closed contactor > never close unless main contactors have been separated. Door lock will > only open electrically but must be closed mechanically otherwise the > normally closed circuit to stop machine will be broken. > > > Anyone with experience? > > Knowledge? > > Or other with any comments in particular about the extra normally closed > contactor? > > > > Regards Nicklas SB Karlsson > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
