USER’S MANUAL
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The Safe torque off function
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, 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 clean-
ing 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.
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.
Compliance
The Safe torque off function of the drive complies with these standards:
EN 60204-1:2006 + AC:2010
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
IEC 61508-1:2010
Functional safety of electrical/electronic/pro-
grammable electronic safety-related systems –
Part 1: General requirements
IEC 61508-2:2010
Functional safety of electrical/electronic/pro-
grammable electronic safety-related systems –
Part 2: Requirements for electrical/electronic/
programmable electronic safety-related systems
Functional safety – Safety instrumented systems
for the process industry sector
IEC/EN 61800-5-2:2007
Adjustable speed electrical power drive systems –
Part 5-2: Safety requirements – Functional
IEC/EN 62061:2005 + A1:2013
Safety of machinery – Functional safety of safety-
related electrical, electronic and programmable
electronic control systems
EN ISO 13849-1:2008 + AC:2009
Safety of machinery – Safety-related parts of
control systems –
Part 1: General principles for design
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