Fault Tracing - ABB ACS880-04 Hardware Manual

280 The Safe torque off function

Fault tracing

The indications given during the normal operation of the Safe torque off function are
selected by drive control program parameter 31.22.
The diagnostics of the Safe torque off function cross-compare the status of the two STO
channels. In case the channels are not in the same state, a fault reaction function is
performed and the drive trips on an "STO hardware failure" fault. An attempt to use the
STO in a non-redundant manner, for example activating only one channel, will trigger
the same reaction.
See the firmware manual of the drive control program for the indications generated by
the drive, and for details on directing fault and warning indications to an output on the
control unit for external diagnostics.
Any failures of the Safe torque off function must be reported to ABB.