Emc Directive Measures For Relay Outputs; Countermeasures; Countermeasure Examples - Omron NJ501-1 Series User Manual

A-5 EMC Directive Measures for Relay
Outputs
The NJ-series Controllers conform to the Common Emission Standards (EN 61000-6-4 or EN 61131-2)
of the EMC Directives. However, noise generated by relay output switching may not satisfy these Stan-
dards when the Controller is incorporated into a system. In such a case, a noise filter must be con-
nected to the load side or other appropriate countermeasures must be provided external to the
Controller.
Countermeasures taken to satisfy the standards vary depending on the devices on the load side, wir-
ing, configuration of machines, etc. Following are examples of countermeasures for reducing the gener-
ated noise.
 Countermeasures
(Refer to EN61000-6-4 for more details.)
Countermeasures are not required if the frequency of load switching for the whole system with the
Controller included is less than 5 times per minute.
Countermeasures are required if the frequency of load switching for the whole system with the Con-
troller included is 5 times or more per minute.
 Countermeasure Examples
When switching an inductive load, connect an surge protector, diodes, etc., in parallel with the load
or contact as shown below.
Circuit
Yes
CR method
C
R
Power
supply
NJ-series CPU Unit Hardware User's Manual (W500)
Current
AC DC
Yes If the load is a relay or solenoid,
there is a delay in the resetting
time.
If the supply voltage is 24 or 48 V,
insert the surge protector in parallel
with the load. If the supply voltage
is 100 to 200 V, insert the surge
protector between the contacts.
Characteristic
The capacitance of the capacitor
should be approx. 1 to 0.5 F per
contact current of 1 A and resis-
tance of the resistor should be
approx. 0.5 to 1  per contact volt-
age of 1 V. These values, however,
vary with the load and the charac-
teristics of the relay. Decide these
values from experiments, and take
into consideration that the capaci-
tance suppresses spark discharge
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 polarity.
Appendices
Required element
A-101