Precautions for i/o modules – Toshiba Programmable Controller PROSEC T3 User Manual

Page 62

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3. Precautions for I/O Modules

(4) If a capacitive load is connected, rush current will flow when

output is changed to ON.
At that time, necessary measures must be taken to protect the
output transistor from being destroyed by the rush current.

To limit the rush current there are two effective measures. One

is to connect a resistor to the load in series. The other is to apply

dummy current to the load by connecting a resistor between the

output terminals.

(5) If an inductive toad is connected, transient overvoltage will occur

when the output is changed to OFF.
This surge voltage will be absorbed into the diode D mentioned

before so that the transistor will be protected. However, if the

output cable is Installed closely to other signal lines, the surge
voltage may cause other problem. In this case, install a flywheel
diode in parallel with the inductive toad (as near as possible to
the toad.)

Output module

Rywtiee) diode

Reverse withstand voltage:

3 times or more of the circuit

voltage

Forward current: load current

or more

If a flywheel diode is connected, the OFF restoration time of the

toad will become longer. If this becomes a problem, connect a

CR snubber circuit to the toad, similar to the countermeasure

taken for surge voltage in AC output.

PROSEC T3