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WAGO-I/O-SYSTEM 750
750-517 2DO 230V AC 1.0A/ Relay 2CO/ Potential Free
Pos : 86 /Serie 750 ( WAGO-I/O-SYST EM)/Ans chli eßen/Anschl uss beispi ele/Digitalausgangs klemmen/Kontaktsc hutz beschaltung für Rel ais klemmen @ 12\mod_1339677705690_21.doc x @ 97510 @ 2 @ 1
6.3
Protective Circuits for Contacts of Relay Modules
Switching off inductive loads such as contactors and solenoid valves can generate
transients with voltage peaks of up to several thousand volts. Very often, these
transients exceed the permissible limits specified in the EMC standards. They
must therefore be limited by using external protective circuits.
Furthermore, they cause an arc, which may destroy the switching contact, and has
a significant impact on the lifetime and safety of the relay. The following
protective circuits, which are directly connected to the source of the interference
in parallel with the consumer, have proved successful in practice:
Table 14: Protective Circuits for Contacts of Relay Modules
Protective Circuits
Figure 15: Diode
Figure 16: Zener Diode
and Diode
Figure 17: Suppressor
Diode
Figure 18: Varistor
Manual
Version 1.1.2
Additional
Defined
Off-Delay
Induction
Voltage
Limitation
long
yes (U
)
D
medium to
yes (U
)
ZD
short
medium to
yes (U
)
ZD
short
medium to
yes (U
VDR
short
Connect Devices
Bipolar
Advantages and
Effective
Disadvantages
Attenuation
Advantages:
•
easy implementation
•
cost-effective and
reliable
•
uncritical
no
dimensioning
•
low induction voltages
Disadvantages:
•
attenuation only via
load resistor
•
long off-delay
Advantages:
•
uncritical
dimensioning
Disadvantages:
no
•
attenuation only above
U
ZD
Advantages:
•
cost-effective
•
uncritical
dimensioning
•
limitation of positive
yes
and negative peaks
•
suitable for AC
voltage
Disadvantages:
•
attenuation only above
U
ZD
Advantages:
•
high power absorption
•
uncritical
dimensioning
)
yes
•
suitable for AC
voltage
Disadvantages:
•
attenuation only above
U
VDR
35
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