Omron ZEN Operation Manual page 17

Conformance to EC Directives
Countermeasures
Countermeasure Examples
Circuit
CR method
Power
supply
xviii
(Refer to EN50081-2 for more details.)
Countermeasures are not required if the frequency of load switching
for the whole system with the ZEN included is less than 5 times per
minute.
Countermeasures are required if the frequency of load switching for
the whole system with the ZEN included is more than 5 times per
minute.
When switching an inductive load, connect an surge protector,
diodes, etc., in parallel with the load or contact as shown below.
Current
AC DC
Yes Yes If the load is a relay or
solenoid, there is a time
lag between the moment
the circuit is opened and
the moment the load is
reset.
If the supply voltage is 24
or 48 V, insert the surge
protector in parallel with
the load. If the supply volt-
age is 100 to 200 V, insert
the surge protector
between the contacts.
Characteristic Required element
The capacitance of the capaci-
tor must be 1 to 0.5 µ F per
contact current of 1 A and
resistance of the resistor must
be 0.5 to 1 Ω per contact volt-
age of 1 V. These values, how-
ever, vary with the load and
the characteristics of the relay.
Decide these values from
experiments, and take into
consideration that the capaci-
tance suppresses spark dis-
charge when the contacts are
separated and the resistance
limits the current that flows
into the load when the circuit is
closed again.
The dielectric strength of the
capacitor must be 200 to 300
V. If the circuit is an AC circuit,
use a capacitor with no polar-
ity.
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