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

Installation and Startup
8.2.7
Arc-Quenching for
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
8 - 28
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
• • operationally by contacts and switches,
• • or by fuses in the event of a fault.
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.
L+
AC Voltage
L
Digital Output
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System Manual
C79000-B8576-C199-03
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