The Safe torque off function 143
Connecting the STO
See STO control unit connections in Connecting the control unit on page 85.
The following diagrams present examples of Safe torque off wiring for
• a single drive unit (page 144)
• multiple drive units (page 145)
• multiple drive units when an external 24 V DC power supply is used (page 146).
Activation switch
In the wiring diagrams below, the activation switch has the designation [K]. This
represents a component such as a manually operated switch, an emergency stop
push button switch, or the contacts of a safety relay or safety PLC.
• If a manually operated activation switch is used, the switch must be of a type that
can be locked out to the open position.
• The contacts of the switch or relay must open/close within 200 ms of each other.
• An FSO-xx safety functions module can also be used. For more information, see
the FSO-xx module documentation.
Cable types and lengths
• Double-shielded twisted-pair cable is recommended.
• Maximum cable lengths:
• 30 m (100 ft) between activation switch [K] and drive control unit
• 60 m (200 ft) between multiple drive units
• 60 m (200 ft) between external power supply and first drive unit
Note: The voltage at the INx terminals of each drive control unit must be at least 17 V
DC to be interpreted as “1”.
Grounding of protective shields
• Ground the shield in the cabling between the activation switch and the control unit
at the control unit.
• Ground the shield in the cabling between two control units at one control unit only.
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