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
The Safe torque off function can be used, for example, to as the final actuator device of
safety circuits that stop the drive in case of danger (such as an emergency stop circuit).
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 of the power
semiconductors of the drive output stage (A, see the diagrams 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 complies with these standards:
NameStandard
Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 60204-1:2016
EN 60204-1:2006 + A1:2009 +
AC:2010
Electromagnetic compatibility (EMC) – Part 6-7: Generic standards – Im-
munity requirements for equipment intended to perform functions in a
safety-related system (functional safety) in industrial locations
IEC 61000-6-7:2014
11
The Safe torque off function 147
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