The Safe torque off functionContents of this chapterThis chapter describes the Safe torque off (STO) function of the drive and gives instructionsfor its use.DescriptionThe Safe torque off function can be used, for example, to as the final actuator device ofsafety 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 enablesshort-time maintenance operations like cleaning or work on non-electrical parts of themachinery without switching off the power supply to the drive.When activated, the Safe torque off function disables the control voltage of the powersemiconductors of the drive output stage (A, see the diagrams below), thus preventing thedrive from generating the torque required to rotate the motor. If the motor is running whenSafe torque off is activated, it coasts to a stop.The Safe torque off function has a redundant architecture, that is, both channels must beused in the safety function implementation. The safety data given in this manual is calculatedfor redundant use, and does not apply if both channels are not used.The Safe torque off function complies with these standards:NameStandardSafety of machinery – Electrical equipment of machines – Part 1: GeneralrequirementsIEC 60204-1:2016EN 60204-1:2006 + A1:2009 +AC:2010Electromagnetic compatibility (EMC) – Part 6-7: Generic standards – Im-munity requirements for equipment intended to perform functions in asafety-related system (functional safety) in industrial locationsIEC 61000-6-7:201418The Safe torque off function 135
