Using Suppression Circuits - Siemens Simatic S7-200 System Manual

2.4

Using Suppression Circuits

General Guidelines
Equip inductive loads with suppression circuits that limit voltage rise on loss of power. Use
the following guidelines to design adequate suppression. The effectiveness of a given design
depends on the application, and you must verify it for a particular use. Be sure all
components are rated for use in the application.
Protecting DC Transistors
The S7-200 DC transistor outputs contain zener diodes that are adequate for many
installations. Use external suppression diodes for either large or frequently switched
inductive loads to prevent overpowering the internal diodes. Figures 2-15 and 2-16 show
typical applications for DC transistor outputs.
Figure 2-15
Figure 2-16
S7-200 Programmable Controller System Manual
C79000-G7076-C230-02
+VDC
Diode Suppression
(1)
+VDC
Zener Diode Suppression
Installing an S7-200 Micro PLC
(1)
(1) IN4001 diode or
equivalent
Inductor
(1) IN4001 diode or
(2)
equivalent
(2) 8.2 V zener, 5 W
Inductor
2-13