The Safe torque off function 199
The Safe torque off function
What this chapter contains
This chapter describes the Safe torque off (STO) function of the drive and gives
instructions for its use.
Description
The Safe torque off function can be used, for example, to construct safety or supervision
circuits that stop the drive in case of danger (such as an emergency stop circuit). Another
possible application is a prevention of unexpected start-up switch 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.
Note: The Safe torque off function does not disconnect the voltage from the drive, see the
warning on page 207.
When activated, the Safe torque off function disables the control voltage of the power
semiconductors of the drive output stage (A, see the diagram below), 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 of the drive complies with these standards:
Standard Name
EN 60204-1 Safety of machinery ā Electrical equipment of machines ā Part 1: General
requirements
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