At a Glance

Some general protective measures are integrated into the channels of discrete input/ouput direct current modules.

DC Outputs

Every static output (except where specifically labeled "Non-Protected"), features a protective device which allows the following to be detected when an output is active:

  • An overload or short circuit. Events such as these cause the output to be deactivated (tripped) and the event to be indicated on the display on the front panel of the module (the LED corresponding to the channel flashes, the I/O LED comes on).

  • Reversal of polarity. An event such as this causes the power supply to short circuit without damaging the module. In order to obtain optimal protection, a quick-blow fuse must be installed on the power supply and upstream from the pre-actuators.

  • Inductive overvoltage. Each output is individually protected against inductive overvoltage and has a fast electro-magnet demagnetization circuit using a zener diode which allows the mechanical cycle of certain fast machines to be reduced.

DC Inputs

24 VDC and 48 VDC inputs are of constant current type. The input current is constant for a voltage greater than:

  • 15 V for 24 VDC inputs

  • 25 V for the 48 VDC inputs

This characteristic has the following advantages:

  • guaranteed minimum current in active state in accordance with IEC standards

  • limited consumed current when input voltage increases, to avoid the module overheating unnecessarily

  • reduced consumed current to the power supply sensor supplied by the PLC power supply or a process power supply