Rockwell Automation 1336E IMPACT Adjustable Frequency AC Drive User Manual V 1-4.XX - Manual (Page 298)

12-16 Troubleshooting
Understanding Precharge and
Ridethrough Faults To understand the precharge and ridethrough faults, you need a basic
understanding of how these functions work, as well as the options that
you can use to alter the way precharge and ridethrough operate in the
1336 IMPACT drive.
Understanding Precharge
The precharge of the drive has different circuits depending on drive
size. For the precharge operation for large horsepower (40 hp and
larger) standalone drives, the precharge starts the SCR phase advance
and completes precharge when the bus is stable. For all other drive
types, precharge is completed after a stable bus voltage is achieved
and the precharge device (SCR or relay) by-passes the precharge
resistor. For common bus operation, set bit 12 in Bus/Brake Opts
(parameter 13). The drive current and voltage ratings stored in
EEProm determine the standalone operation.
With the default configuration, the following conditions are needed to
complete precharge:
• a stable bus voltage for a minimum of 300 milliseconds
• a bus voltage greater than the value set in Line Undervlts
(parameter 27)
• a valid control status from the precharge board, if present
You can modify the default configuration for common bus drives by
using the external fault (input) and the precharge exit option:
• You can use the external fault input with a cabinet disconnect
switch to force precharge when the disconnect is opened and the
drive is disabled. This may reduce current stress when the
disconnect is closed again.
• You can use the exit precharge option to let the precharge
complete after the precharge timeout period (30 seconds) when
the bus voltage is not stable. All other conditions must be met.
This is often used in the case of common or shared bus
configurations where other drive(s) may be causing bus voltage
variations. Only use this option where needed otherwise
excessive inrush current could open or weaken the line fuses.
Before you can enable the inverter, all drive types must complete a
first time precharge. This is required even if you have set the disable
precharge function by setting bit 14 of Bus/Brake Opts
(parameter 13).
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
tracker’s voltage value before starting again.
file: Application
group: Bus Control
file: Fault Setup
group: Fault Limits