SLC 500 Digital I/O Modules 15
Publication 1746-IN027D-EN-P - December 2012
E-FUSE LED Indicator
Auto Reset Operation
Short Circuit/Overload Current Diagnostics
If a short circuit or overload current condition occurs on an output channel:
• the E-FUSE LED indicator will illuminate provided that power is applied to the module.
Power required: 5V DC via backplane and load power via an external supply.
• all other channels continue to operate as directed by the CPU (processor) module.
The 1746-OB6EI and 1746-OB16E modules perform auto-reset under overload
conditions. When an output channel overload occurs, that channel will limit
current within milliseconds after its thermal cut-out temperature has been
reached. While in current limit, the output channel can cool below the thermal
cut-out temperature allowing the module to auto-reset and resume control of the
output channel as directed by the processor until the thermal cut-out
temperature is again reached.
Removing power from an overloaded output channel would also allow the output
channel to cool below the thermal cut-out temperature, allowing auto-reset to
occur when power is restored. The output channel would operate as directed by
the processor until the thermal cut-out temperature is again reached.
To avoid auto-reset of an output channel under overload conditions, an external
mechanical fuse can be used to open the circuit when overloaded.
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