User`s manual

7-23
[2] Precautions for operating the output module
(1) Protection from output short circuit
In case of a short circuit of the load connected to an output terminal, output devices and print
board may be burned. Be sure to insert a protection fuse in the output.
Some modules have a built-in fuse per common line for protection of the module from heating and
burning due to excessive current. It is not intended, however, for protection of the output devices
and load from excessive current; therefore, insert fuse for each line outside the module. This is
also advisable from maintenance point of view.
(2) Countermeasure to surge current of lamp load
At turning ON an incandescent lamp, there is surge current 10 to 20 times bigger than normal
current for several 10ms. For reduction of the surge current, insert either a bleeder resistance or
an electric current limit resistance.
1) To insert a bleeder resistance
During the OFF state of the output module, keep supplying dark current so small as to turn on
the lamp dimly.
2) To insert an electric current limit resistance
This limits the current within a value determined by the value of the current limit resistance.
When the resistance value is high, the voltage on the lamp decreases. Determine the resistance
value by the brightness needed when turning ON the lamp.
Output module
Load
Fuse
COM
Power supply load
1
0
Bleeder
resistance
Output
module
Surge killer
L load