Fault Tracing - ABB ACH480 Hardware Manual

Safe torque off function 139

Fault tracing

The indications given during the normal operation of the Safe torque off function are
selected by drive parameter 31.22. The indications can be read via fieldbus. The
indications are not safety-classified signals.
The diagnostics of the Safe torque off function cross-compare the status of the two
STO channels. If the channels are not in the same state, a fault reaction function is
done 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, triggers
the same reaction.
See the drive firmware manual 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.