Discrete I/O Modules 41
Publication 1746-IN005A-US-P
Auto Reset Operation
Short Circuit/Overload Current Diagnostics
If a short circuit or overload current condition occurs on an output channel:
1. The E-Fuse LED will illuminate provided that power is applied to the
module. Power required: 5V dc via backplane and load power via an
external supply.
2. All other channels continue to operate as directed by the CPU (processor)
module.
Recovery From Channel Shutdown
1. Remove the SLC 500 system power and correct the conditions causing the
short circuit or overload current condition.
2. Restore the SLC 500 system power. The module automatically resets and
resumes control of the output channel and associated load.
IMPORTANT: The 1746-OB6EI and -OB16E perform auto-reset under overload
conditions. When an output channel overload occurs as described
on page 40, 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.
Allen-Bradley Spares
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