Rockwell Automation 1746-HSCE2 Multi-Channel High Speed Counter Module - Manual (Page 46)

Publication 1746-UM002B-EN-P - August 2004
3-6 Installation and Wiring
Electronic Protection The electronic protection of the 1746-HSCE2 has been designed to
provide protection for the module from overload current conditions.
The protection is based on a thermal cut-out principle. In the event of
a short circuit or overload current condition on an output channel, all
channels will turn off within milliseconds after the thermal cut-out
temperature has been reached.
Auto Reset Operation
IMPORTANT
The module does not provide protection against
reverse polarity wiring or wiring to AC power
sources. Electronic protection is not intended to
replace fuses, circuit breakers, or other
code-required wiring protection devices.
IMPORTANT
1746-HSCE2 outputs perform auto-reset under
overload conditions. When an output channel
overload occurs as described above, all channels
turn off within milliseconds after the thermal cut-out
temperature has been reached. While the
overcurrent condition is present, the module tries
resetting the outputs at intervals of 500 ms. If the
fuse cools below the thermal cut-out temperature, all
outputs auto-reset and resume control of their
external loads as directed by the module until the
thermal cut-out temperature is again reached.
Removing power from an overloaded output
channel would also allow the fuse to cool below the
thermal cut-out temperature, allowing auto-reset to
occur when power is restored. The output channels
then operate as directed by the module until the
thermal cut-out temperature is again reached.
To avoid auto-reset of output channels under
overload conditions, monitor the fuse blown status
bit (FB1) in the module’s status file and latch the
outputs off when an overcurrent condition occurs.
An external mechanical fuse can also be used to
open output circuits when they are overloaded.