Safe Torque Off (Option +Q967) - ABB ACS800 Series Hardware Manual

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Safe torque off (option +Q967)

The drive supports the Safe torque off (STO) function according to standards:
• EN 61800-5-2:2007,
• EN ISO 13849-1:2008,
• IEC 61508,
• IEC 61511:2004,
• EN 62061:2005.
The function also corresponds to Prevention of unexpected start-up of EN 1037.
The STO may be used where power removal is required to prevent an unexpected
start-up. The function disables the control voltage of the power semiconductors of
the drive output stage, thus preventing the drive from generating the voltage
required to rotate the motor (see diagram below). By using this function, short-time
operations (like cleaning) and/or maintenance work on non-electrical parts of the
machinery can be performed without switching off the power supply to the drive.
WARNING! The Safe torque off function does not disconnect the voltage of the main
and auxiliary circuits from the drive. Therefore maintenance work on electrical parts
of the drive or the motor can only be carried out after isolating the drive system from
the main supply.
Note: The Safe torque off function can be used for stopping the drive in emergency
stop situations. In the normal operating mode, use the Stop command instead. If a
running drive is stopped by using the function, the drive will trip and stop by coasting.
If this is not acceptable, e.g. causes danger, the drive and machinery must be
stopped using the appropriate stopping mode before using this function.
Note concerning permanent magnet motor drives in case of a multiple IGBT
power semiconductor failure: In spite of the activation of the Safe torque off
function, the drive system can produce an alignment torque which maximally rotates
the motor shaft by 180/p degrees. p denotes the pole pair number.
For more information on the installation of the Safe torque off function, see chapter
Installation of the ASTO board (Safe torque off,
For more information on the Safe torque off function and the relevant safety data,
see ACS800-01/04/11/31/104/104LC Safe torque off function (+Q967), Application
guide (3AUA0000063373 [English]).
An example circuit diagram is shown below.
Planning the electrical installation
+Q967).