ABB ACS880-04F-504A-3, Hardware Manual

Page: 171 / 202

The Safe torque off function
Contents of this chapter
This chapter describes the Safe torque off (STO) function of the drive and gives
instructions for its use.
Description
WARNING!
In case of parallel-connected drives or dual-winding motors, the STO must be
activated on each drive to remove the torque from the motor.
The Safe torque off function can be used, for example, as the final actuator device of
safety circuits (such as an emergency stop circuit) that stop the drive in case of danger.
Another typical application is a prevention of unexpected start-up function that enables
short-time maintenance operations like cleaning or work on non-electrical parts of
the machinery without switching off the power supply to the drive.
When activated, the Safe torque off function disables the control voltage for the power
semiconductors of the drive output stage, thus preventing the drive from generating
the torque required to rotate the motor. If the motor is running when Safe torque off
is activated, it coasts to a stop.
The Safe torque off function has a redundant architecture, that is, both channels must
be used in the safety function implementation. The safety data given in this manual
is calculated for redundant use, and does not apply if both channels are not used.
The Safe torque off function complies with these standards:
Name Standard
Safety of machinery – Electrical equipment of machines – Part 1:
General requirements IEC 60204-1:2016
EN 60204-1:2018
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The Safe torque off function 171