Appendix C Notes on Applying the I/O Modules
6F8C1575
120
(6) If the inductive load is connected to an output module, a transient voltage with a
relatively large energy is generated at OFF time. This surge voltage is absorbed
with Diode D mentioned above to protect the transistor.
If the external wiring is used for routing, this surge voltage may have an adverse
affect on other signal systems. To prevent this, install the surge absorbing element
in parallel to the inductive load as shown in Figure C.3-11.
Figure C-13 Connection of inductive load
For the surge absorbing element, select one
suitable for application
Freewheeling
Reverse withstand voltage:
diode 3 times or more relative to the supply voltage
(For voltage clamp) Forward current: Greater than the load current
Varistor
A varistor the rated voltage of which is more
(For voltage clamp)
than about twice the maximum supply voltage
Snubber (CR) circuit
R: 0.5 to 1 Ω for 1 V coil voltage
(For attenuation of
C: 0.5 to 1 F for 1A coil current
high frequency) (Nonpolar capacitor)
L
Transistor
output
module
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