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
±
i
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.
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PROSEC T3