Rockwell Automation 1336T FORCE Series B - Manual (Page 222)

Chapter 6
Troubleshooting
6–10
A filtered, or slow, average of the bus voltage is developed as a
reference, or bus voltage tracker, to determine if a line drop out has
occurred. If a 150 volt (or greater) drop in present bus voltage compared
to the filtered bus voltage occurs, the drive can start a ridethrough. The
ridethrough function:
•
disables the drive
•
restarts a precharge
•
waits for the bus to return to within 75 volts of the bus voltage track-
er’s voltage value before starting again.
You can use bits 0–4 of Bus/Brake Opts to control the slew rate of the
bus voltage tracker. Refer to the section on the bus voltage tracker later
in this chapter for additional information.
Understanding Ridethrough
Ridethrough provides current inrush protection and extended logic
operating time if the power lines drop out while the drive is running.
The drive is immediately disabled when it senses that the incoming
power lines dropped out (bus capacitor voltage drop). The energy stored
in the bus capacitors keeps the logic supplies running for an extended
time. If the power lines return before the logic power supplies lose
power, you can configure the drive to resume operation without system
intervention (default). The ridethrough timeout is set for two seconds.
This means that the drive is configured to fault (default setting) and not
auto–restart if the dropout lasts more than two seconds.
!
ATTENTION: You must determine safe auto–restart and
fault configurations at the system and user level. Incorrect
selection(s) may result in safety concerns and/or drive
damage.
CP Fault / Warning Configuration Select 1 (parameter 86) and CP
Warning / None Configuration Select (parameter 87) let you specify how
you want the drive to report specific precharge and ridethrough
information.
Ridethrough also protects the drive from excessive inrush current when
the power returns by entering a precharge mode when ridethrough is
initiated. After precharge has finished, the drive can complete
ridethrough and resume normal drive operation. The drive is enabled
again after the bus rises to within 75 volts of the bus voltage tracker
value.