User`s manual

7-24
(3) Countermeasure to surge voltage at opening/closing induced load
Some load generates surge voltage of several thousands volt when an induced load is operated or
closed its circuit. All output module except the relay output module have a circuit to absorb surge
within module. However, when the wiring to the load is long, its effectiveness is reduced and a
surge countermeasure is required in the load side as well. In case of the relay output module
without surge absorption circuit, surge countermeasure outside the module is indispensable in
case the load generates high voltage. (This surge voltage countermeasure can extend the life time
of the contact points of the relay.)
Surge voltage countermeasure
Relay output module
Relay output module
Transistor output module, FET output module
Triac output module
CR surge killer: C: 0.033 to 0.33 mF (Pressure resistance of over 250 VAC)
R: 47 to 120 ohm
Example of CR surge killer
Diode: Peak inverse voltage (V
RM
) is more than three times of the load voltage.
Average rectified current (Io) is more than load current.
In case of AC load, a varistor can be used in place of the CR surge killer for the same effect.
(Installation of both of the CR surge killer and the varistor increases the effect.)
RC
For 100 VAC
For 200 VAC
953M2503 10411(0.1 m + 120 ohm) (made by Matsuo Electric Co., Ltd.)
953M5003 33311(0.033 m + 120 ohm) (made by Matsuo Electric Co.,Ltd.)
For 85 to 132 VAC
For 170 to 264 VAC
TN R12G221K (made by Marcon Co., Ltd.), NV220D14 (made by NEC)
TNR12G431 K (made by Marcon Co., Ltd.), NV430D14 (made by NEC)
Surge killer
L load
Diode
L load
＋
−
Diode
L load
＋
−
Surge killer
L load
(In case of contact
points in series line)