Arc-Quenching For Inductive Loads - Siemens S5-135U/155U System Manual

8.2.7

Arc-Quenching for Inductive Loads

Note
Digital output modules have integrated circuits on the module to quench
inductive loads (refer to the technical specifications of the output modules).
Exception: The 458 digital output module allows the switching of inductive
loads with contact protection submodules.
The integrated circuits on the modules for quenching inductive loads are
disabled if the load circuits are interrupted, either
This can result in excessive, inductive breaking voltages which put fault-free
operation at risk.
You can prevent this with additional, external quenching circuitry for the
inductive loads.
DC Voltage
Digital Output
Contact, Switch
Contactor,
Solenoid Valve, etc.
L–
Quenching Device
(Diode, Zener Diode, R/C Network or Varistor)
Figure 8-14 Quenching of Inductive Loads when the Load Circuit is Opened
System Manual
C79000-G8576-C199-06
operationally by contacts and switches,
or by fuses in the event of a fault.
L+
Digital Input/Output Modules
AC Voltage
L
Digital Output
ELR
ELR
ELR
N
8-25