Wiring
For the electrical specifications of the STO connection, see the technical data of the control
unit.
￭ Activation switch
In the wiring diagrams, 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.
• In case 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 or an FPTC-0x thermistor protection module can
also be used. For more information, see the module documentation.
￭ Cable types and lengths
• Double-shielded twisted-pair cable is recommended.
• Maximum cable lengths:
• 300 m (1000 ft) between activation switch [K] and drive control unit
• 60 m (200 ft) between multiple drives or inverter units
• 60 m (200 ft) between external power supply and first control unit
Note: A short-circuit in the wiring between the switch and an STO terminal causes a
dangerous fault. Therefore, it is recommended to use a safety relay (including wiring
diagnostics) or a wiring method (shield grounding, channel separation) which reduces or
eliminates the risk caused by the short-circuit.
Note: The voltage at the STO input terminals of the control unit must be at least 17 V DC
to be interpreted as “1”.
The pulse tolerance of the input channels is 1 ms.
￭ Grounding of protective shields
• Ground the shield in the cabling between the activation switch and the control unit at
the control unit only.
• Ground the shield in the cabling between two control units at one control unit only.
The Safe torque off function 213
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