Siemens SIMATIC S7-1500 System Manual page 131

Connection cables for digital inputs and digital outputs
Use rigid or flexible cables with a conductor cross-section as specified in the SIMATIC Drive
Controller manual for wiring the inputs/outputs.
Note
Maximum permissible cable length
The maximum permissible cable length for the connection cable is 30 m.
Inductive loads
When you use the digital inputs in combination with inductive loads, you must ensure that
the permissible voltage range of the digital inputs from -30 V to +30 V is not exceeded by the
switching overvoltage of inductive loads.
You best avoid the overload by using auxiliary contacts at the contactor/relay for the digital
inputs. If no auxiliary contacts are available, you must integrate an overvoltage protection.
Protective wiring with overvoltage protection diode, or a diode combination with Zener diode
are possible as overvoltage protection. RC elements and varistors are not suitable due to the
residual voltages.
Overvoltage protection for signal lines
Overvoltage protection devices are required for lines of > 30 m. You are advised to use the
following snubber to protect the 24 V signal lines from overvoltage:
Table 8- 2
Line
24 V signal lines
Snubbers must always be positioned at the edge of the area to be protected, for example at
the entry to the cabinet. All 24 V lines leaving the protected area must run through a
snubber. You can find additional information on overvoltage protection in the SINAMICS
S120 manual "Booksize Power Units
(https://support.industry.siemens.com/cs/ww/en/view/109781351)".
Additional information
Additional information on the pin assignment of interfaces X122, X132, X142 can be found
in the SIMATIC Drive Controller manual
(https://support.industry.siemens.com/cs/ww/en/view/109766666).
SIMATIC Drive Controller
System Manual, 11/2023, A5E46600094-AD
8.7 Digital inputs and digital inputs/outputs X122, X132 and X142
Recommendations for overvoltage protection
Overvoltage protection device
Manufacturer: Weidmüller article: MCZ OVP TAZ
Article number: 844915 0000
Connecting
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