ABB ACS255 User Manual page 25

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5.10.7. "STO" Electrical Installation
The "STO" wiring shall be protected from inadvertent short circuits or tampering which could lead to failure of the "STO" input signal,
further guidance is given in the diagrams below.
In addition to the wiring guidelines for the "STO" circuit below, section 5.1.1 "Recommended installation for EMC compliance should also be
followed.
The drive should be wired as illustrated below; the 24Vdc signal source applied to the "STO" input can be either from the 24Vdc on the drive or
from an External 24Vdc power supply.
5.10.7.1.
Using an External 24Vdc Power Supply.
Safety relay
External
+24Vdc
Power
0V
Supply
1 2 3 4 5 6 7 8 9 10 11 12 13
External
+24Vdc
Power
Supply
Note : The Maximum cable length from Voltage source to the drive terminals should not exceed 25 metres.
5.10.7.2.
Voltage Rating (Nominal)
STO Logic High
Current Consumption (Maximum)
5.10.7.3.
The safety relay should be chosen so that at minimum it meets the safety standards in which the drive meets.
Standard Requirements
Number of Output Contacts
Switching Voltage Rating
Switching Current
Recommended "STO" wiring
Protective Capped Trunking
or equivalent to prevent
STO Cable short circuit to an
external Voltage source.
- Twisted-Pair
- Shielded cables
Safety relay
0V
External Power supply Specification.
24Vdc
18-30Vdc (Safe torque off in standby)
100mA
Safety Relay Specification.
SIL2 or PLd SC3 or better (With Forcibly guided Contacts)
2 independent
30Vdc
100mA
Using the drives on-board 24Vdc supply
Protective Capped Trunking
or equivalent to prevent
STO Cable short circuit to an
external Voltage source.
Safety
1213
relay
1 2 3 4 5 6 7 8 9 10 11 12 13
Wires should be
protected
against short
circuits as
shown above
1 7
1213
Protected
shielded cables
Safety relay