FATEK FBs-CBE - Protection of Transistor Output and Noise Suppression

H7-8
7.5.2 Protection of Transistor Output and Noise Suppression
The transistor output in FBS-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.
D : 1N4001 diode or
equivalent device
PLC Relay output
Inductive load
VDC
D
Suppress by a diode (for low power)
D : 1N4001 diode or
equivalent device
ZD : 9V Zener, 5W
PLC Relay output
Inductive load
VDC
ZD
D
Suppress by a diode + Zener (high power and frequent ON/OFF)