Omron CJ2 CPU UNIT User Manual page 416

Appendices
Circuit
No
Diode method
Power
supply
Yes
Varistor method
Power
supply
When switching a load with a high inrush current such as an incandescent lamp, suppress the inrush
current as shown below.
Countermeasure 1
OUT
R
COM
Providing a dark current of
approx. one-third of the rated
value through an incandescent
lamp
A-154
Current
AC DC
Yes The diode connected in parallel
with the load changes energy accu-
mulated by the coil into a current,
which then flows into the coil so
that the current will be converted
into Joule heat by the resistance of
the inductive load.
This time lag, between the moment
the circuit is opened and the
moment the load is reset, caused
by this method is longer than that
caused by the CR method.
Yes The varistor method prevents the
imposition of high voltage between
the contacts by using the constant
voltage characteristic of the varis-
tor. There is 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 varistor in parallel with
the load. If the supply voltage is
100 to 200 V, insert the varistor
between the contacts.
Countermeasure 2
OUT
COM
Providing a limiting resistor
Characteristic
R
Required element
The reversed dielectric strength
value of the diode must be at least
10 times as large as the circuit volt-
age value. The forward current of
the diode must be the same as or
larger than the load current.
The reversed dielectric strength
value of the diode may be two to
three times larger than the supply
voltage if the surge protector is
applied to electronic circuits with
low circuit voltages.
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CJ2 CPU Unit Hardware User's Manual