Siemens SIMATIC ET 200PA SMART - Page 149

Example
The following diagram shows an output circuit that requires additional overvoltage protection
devices.


,0

36
6060606060606060
① Contact in output circuit
② Inductor requires a protection circuit
Figure 10-3 Relay contact for EMERGENCY STOP in output circuit
Protection circuit of DC-actuated coils
DC-actuated coils are connected to diodes or Zener diodes as shown in the following figure.





① With diode
② With Zener diode
Figure 10-4 Protection circuit of DC-actuated coils
The protection circuit with diodes/Zener diodes has the following properties:
● Trip overvoltages can be completely prevented. Zener diode has a higher trip voltage.
● High trip delay (6 to 9 times higher compared to case without protection circuit).
Zener diode trips faster than diode protection circuit.
ET 200PA SMART I/O modules
10.3 Digital output modules
ET 200PA SMART
Operating Instructions, 06/2019, A5E34192013-AB 149