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168 The Safe torque off function
•
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.
￭
Cable types and lengths
•
ABB recommends double-shielded twisted-pair cable.
•
Maximum cable lengths:
•
300 m (1000 ft) between activation switch [K] and drive control unit
•
60 m (200 ft) between multiple drives
•
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 drive must be at least 13 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.
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