What This Chapter Contains - ABB ACS880-37 Hardware Manual

The Safe torque off function

What this chapter contains

This chapter describes the Safe torque off (STO) function of the inverter (ie. the inverter
unit 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 inverter 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 inverter.
When activated, the Safe torque off function disables the control voltage of the power
semiconductors of the inverter output stage (A, see diagram below), thus preventing the
inverter 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 inverter complies with these standards:
Standard
EN 60204-1:2006 + AC:2010
IEC 61326-3-1:2008
Name
Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
Electrical equipment for measurement, control and laboratory use – EMC
requirements – Part 3-1: Immunity requirements for safety-related
systems and for equipment intended to perform safety-related functions
(functional safety) – General industrial applications
The Safe torque off function 223
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