What would cause an SAFF (Safety Function Error) fault on a Process Drive?

Issue:
SAFF (Safety Function Error) fault on a Process Drive

Product Line:
Altivar Process Drives

Environment:
All

Cause:
NA

Resolution:

SAFF occurs if STOA and STOB are at different levels (one on and one off).  This indicates the safety monitoring circuit is not in a good condition so it will trip the drive, preventing it from operating.

Review wiring connections between 24V, STOA and STOB terminals to ensure proper signals are present.  If both STOA has 24VDC present and STOB does not (or B is on and A is not), the SAFF will be triggered.  Check terminals for a good connection, check external wiring for the source of the discrepancy.
Use the Logic Input Map (available in Menu 4: Display, then go to I/O Map and then Logic input map) to view the status of the inputs according to the drive and compare to measurements made between COM and STOA as well as COM and STOB.
If voltage is measured on each input, but the Logic Input Map does not show both STOA and STOB are on (up in the image) then there may be an issue with drive.

Noise is a possible cause of SAFF, so to test, remove the external wires and install jumpers between 24V, STOA and STOB.  Then test (if safe to do so) and if SAFF no longer occurs, closely review the wiring to STOA/STOB wiring.  Separate from power wiring.  Use shielded cable to help reduce noise.

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