FATEK M Series User Manual page 56

Suppression of Counter-Electromotive Force
For the inductive load, whether in AC or DC power, suppression devices must be connected in parallel
to both its ends to protect the relay contacts and lower noise interference. The schematic diagrams for AC
and DC powers are shown below, respectively:
Suppress by a diode + Zener in DC power load (for high power and frequent ON/OFF)
6-4-2 Protection of Transistor Output and Noise Suppression
The transistor output in M-Series PLC already includes Zener diode for counter-electromotive force,
which is sufficient for low power inductive load and medium frequency of ON/OFF application. In
conditions of high power or frequent ON/OFF, please construct another suppression circuit to lower noise
interference and prevent voltage from exceeding the limit or overheating that may damage the transistor
output circuit.
Scheme of AC power load
Suppress by a diode in DC power load (for low power）
8
Chapter 6 Digital Output Circuit
M-Series PLC Expansion Module User Manual