ABB ACS880-07, Hardware Manual

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The Safe torque off function
Contents of this chapter
This chapter describes the Safe torque off (STO) function of the inverter unit of the
ACS880-07 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:
Name Standard
Safety of machinery – Electrical equipment of machines – Part 1: General
requirements EN 60204-1:2016
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 IEC 61326-3-1:2008
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