Hi and also Welcome to the Forum!
wine_sparky said:
If I give my PF 40p a STO signal, then attempt to restart after, it won't. No Faults.
I end up having to remove the start and FWD command, then re-apply them.
After doing that, the drive will run.
Any thoughts?
For a minimum Category 3 / Performance Level d (Cat3/PLd) Safety function, as well as tripping the STO you must also disable the drive (remove Enable) and assert a Stop (includes removing the Start).
Note: On the PowerFlex 40P (and PowerFlex 70 Class) drives, the STO option module has only one Safety channel input. However, the Enable input is a solid state input which acts as a second Safety channel input.
The Safety relay (or controller) when tripped will open its output circuits which should then remove power from both the STO and Enable inputs. This provides a level of redundancy in disabling the drive.
Atop that, the Safety relay (or controller) output circuits should also remove power to the Stop/Start inputs, asserting a Stop to the drive. As the power for a Stop, Start and a FWD input circuit, etc., are typically all from the same source, this should mean that the Safety function will simultaneously remove the power from all these control inputs.
The STO module on your drive also provides an auxiliary "Monitor Contact" which you should wire to the Safety function's monitored reset circuit, if required.
Only after the Safety relay (or controller) has been reset, and the STO and Enable inputs are restored, should a valid Start/FWD command be issued to the drive. Depending on where these commands are issued from (hard wiring or controller, etc.), you must ensure the above is implemented.
On the topic of automatically restarting these drives in general, there is indeed also a standard auto reset/restart feature on these drives. We may set certain parameters to allow an automatic reset/restart after a Type 1 Fault (Example: Motor Overload). This is just to inform in general that it should not be thought of as "not ever permitted" to automatically restart these drives.
What should determine whether this feature would be allowed or not is a Risk Assessment (dirty words again). Certain machines, operations or processes may indeed be perfectly safe in having a function restart automatically, if assessed as such. But as Ken mentions, "typically" for Safety functions, on relatively dangerous equipment, this tends not to be permitted.
For more information, clarification, and verification on the above, please reference the following manual for your DriveGuard Safe Torque Off Option...
https://literature.rockwellautomation.com/idc/groups/literature/documents/um/pflex-um003_-en-p.pdf
Note: Page 17 tables the status of the STO/Enable channels, along with the auxiliary status signals made available in the drive.
Regards,
George